Michael Bardanis - Academia.edu (original) (raw)

Papers by Michael Bardanis

Research paper thumbnail of Long-term monitoring and behaviour of mudbricks and small mudbrick walls (in Greek)

9th Hellenic Conference on Geotechnical Engineering, 2023

The drying of full-size mudbricks and small mudbrick walls was investigated for various hay conte... more The drying of full-size mudbricks and small mudbrick walls was investigated for various hay contents by monitoring suction and volumetric water content as these were measured on sensors installed inside mudbricks and mudbrick walls. A higher drying rate is observed with increasing hay content. Mudbrick walls exhibit smaller uniaxial compressive strength compared to cubes sized 10x10x10cm. As the the size of mudbricks is increased, a tendency for uniaxial compressive strength with the increase of the wall size is observed.

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Research paper thumbnail of Investigation of index and mechanical properties of mudbricks from the ancient walls of Eleusis (in Greek)

9th Hellenic Conference on Geotechnical Engineering, 2023

Samples of ancient mudbricks from the remnants of the ancient walls of the Eleusis Sanctuary were... more Samples of ancient mudbricks from the remnants of the ancient walls of the Eleusis Sanctuary were tested. Their index and mechanical properties were measured and on the basis of these results, soil material from the archaeological site with the same properties was identified. This was subjected to compaction with various compaction energies per volume and hay content that allowed the determination of a suitable compaction energy per volume and hay content leading to the reproduction of new mudbricks with properties as close as possible to the ancient ones.

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Research paper thumbnail of Moisture Migration Under Mat Foundations in Nicosia Marl

Geotechnical and Geological Engineering, 2018

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Research paper thumbnail of A simplified approach to estimating the evolution of residual shear strength of unsaturated soils with suction

E3S Web of Conferences, 2023

Several researchers have investigated the effect of suction and partial saturation on the angle o... more Several researchers have investigated the effect of suction and partial saturation on the angle of residual shear strength. Most of these investigations involve the adoption and application of a method of controlling suction on the ring shear apparatus and performing ring shear tests on the same soil for various values of suction. Methods adopted include both the axis translation technique for control of suction over the range 50-1500 kPa and the saturated salt solutions method for control of suction in the range of several MPa. The general picture from these investigations is that the residual shear strength failure envelope remains linear but corresponding to higher values of the angle of residual shearing resistance for constant suction; this value increasing with increasing suction. The paper presents an attempt to normalise values of measured angle of residual shearing resistance for various suction values with the angle of residual shear strength of the corresponding fully saturated soil. This normalisation verified the linear increase of the ratio tanφres(s)/tanφres(s=0) with suction. This linear increase allows for estimation of the evolution of tanφres(s) with suction if φres(s) for one specific suction can be measured. This observation led to the measurement of tanφres(s) of clayey soils in conventional ring shear apparatus without suction control, simply by removing water from the shear box while shearing continues and measuring shear strength until its stabilisation, taking place after the specimen in the shear box came to equilibrium with prevailing laboratory atmospheric conditions. Using the chilled mirror hygrometer to measure equilibrium suction after ring shear completion indicated that equilibrium suction due to laboratory atmospheric conditions is practically constant over the time needed for a single test on one soil. This observation along with the previous observation on the linear increase of the ratio tanφres(s)/tanφres(s=0) with suction, makes valid the estimation of evolution of residual shear strength of unsaturated soils with suction using only a conventional ring shear apparatus and a chilled mirror hygrometer. The paper concludes by outlining the approach, presenting measurements and a relation obtained between tanφres(s)/tanφres(s=0), suction and liquid limit.

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Research paper thumbnail of Investigation of the properties and behaviour of ancient and newly constructed mudbricks from the ancient walls of Eleusis

E3S Web of Conferences, 2023

The paper presents the test results from the investigation of the nature and mechanical behaviour... more The paper presents the test results from the investigation of the nature and mechanical behaviour of mudbricks from the ancient mudbrick wall of Eleusis in Attica, Greece. The mudbrick wall remains preserved to date in the site of Eleusis are some of the largest preserved in Greece. Small fragments of mudbricks were taken to the laboratory for experimental investigation. Testing included index tests to classify the soil material the mudbricks were made of, mineralogical analyses of their fines' content, mechanical testing suitable for the nature of the materials and the ability to trim the samples without causing damage and measurements of suction on samples as they were obtained, further dried, or rewetted. The soil material used for ancient mudbrick construction was a silty sand to sandy silt with a small fraction clay content, with marginally plastic to non-plastic fines. Dry unit weight was found to be close to the dry unit weight of fresh mudbrick material after being compacted with a minimum compaction energy of only 45 kNm/m 3 and left to dry to residual water content conditions. Similarly, field water content was found close to the residual water content of these recompacted soil samples. Consequently, unconfined compression strength was found very high corresponding to the residual water content condition, with similarly high cohesion obtained from direct shear tests and a very high yield stress under one-dimensional conditions of loading.

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Research paper thumbnail of A simplified approach to estimating the evolution of residual shear strength of unsaturated soils with suction

E3S Web of Conferences

Several researchers have investigated the effect of suction and partial saturation on the angle o... more Several researchers have investigated the effect of suction and partial saturation on the angle of residual shear strength. Most of these investigations involve the adoption and application of a method of controlling suction on the ring shear apparatus and performing ring shear tests on the same soil for various values of suction. Methods adopted include both the axis translation technique for control of suction over the range 50-1500 kPa and the saturated salt solutions method for control of suction in the range of several MPa. The general picture from these investigations is that the residual shear strength failure envelope remains linear but corresponding to higher values of the angle of residual shearing resistance for constant suction; this value increasing with increasing suction. The paper presents an attempt to normalise values of measured angle of residual shearing resistance for various suction values with the angle of residual shear strength of the corresponding fully sat...

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Research paper thumbnail of Reproduction and long-term monitoring of drying of mudbricks and small mudbrick walls for the preservation of the ancient mudbrick wall of Eleusis

E3S Web of Conferences

The mudbrick wall remains preserved to date in the site of Eleusis are some of the largest preser... more The mudbrick wall remains preserved to date in the site of Eleusis are some of the largest preserved in Greece. Following an extensive investigation of the properties of existing mudbricks, material of similar properties from the archaeological site of Eleusis was used to reproduce mudbricks of similardensity with the ancient ones after drying with various concentrations of dry grass also from the archaeological site. Actual mudbricks were reproduced and brought to a final equilibrium condition under climatic conditions practically similar to those in Eleusis. Others were used to trim samples and measuremechanical properties to compare with original mudbricks, others were instrumented with suction and volumetric water content sensors in order to monitor mudbrick drying under climatic conditions and others in order to build small mudbrick walls with mortar from the same soil used to make the mudbricks. These small mudbrick walls included the mudbricks with internally installed suctio...

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Research paper thumbnail of Some examples and lessons from long-term field measurements of suction in Greece

E3S Web of Conferences

The occurrence of unsaturated soils in the field has been well documented worldwide by measuremen... more The occurrence of unsaturated soils in the field has been well documented worldwide by measurements of the degree of saturation on samples taken during geotechnical investigations. On the other hand, the suction of unsaturated soils in the field, especially as part of long-term measurements, is documented very rarely and references on the subject are very few and for very few places around the world. The scarceness of this kind of measurements denies researchers perception of the anticipated suction and its possible loss, or retention, as a result of climatic conditions, especially in countries with warm temperate climate. Suction measurements from temporary and permanent stations in Greece and Cyprus have been presented in the past showing that considerably high values of suction can develop and be maintained even during wet periods. This paper focuses on examples and lesson learned from stations in Greece, especially magnitude and change of suction with time, as well as longevity ...

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Research paper thumbnail of ROADS UNDER AIRPORTS: A CASE STUDY FROM INTERNATIONAL AIRPORT “DIAGORAS” ON RHODES ISLAND AND ITS LABORATORY AND FIELD INVESTIGATION (in Greek)

HSSMGE one-day conference on Geotechnical Engineering and Pavement Design, 2022

Runway 07-25 of “Diagoras” Inter¬national Airport on Rhodes island in Greece was suffering persis... more Runway 07-25 of “Diagoras” Inter¬national Airport on Rhodes island in Greece was suffering persistent pavement distresses at ch. 1+395. Surface depressions were very regularly recorded at approximately 3.5m to the left and right of the axis of the runway, with rapidly evolving extent during periods of heavy aircraft traffic or after heavy rainfall incidents follow¬ing prolonged dry periods. Satellite images and airport maintenance log reviews revealed that these distresses appeared systematically at the sa¬me location very soon, even after every superficial rehabilitation of the pavement. The desk study carried out during the recon¬nais¬sance phase of the problem revealed that the problematic pavement section coincides with the alignment of an old road that existed prior to airport construction. This road which used to connect the nearby Paradeisi village with the seashore seemed to remain a direct buried con¬duit for subsurface drainage towards the sea, as also revealed from the outflow location of fire-fighting vehicles’ foam after an aviation safety incident that happened near the problematic pavement area. A thorough geotechnical inve¬sti¬gation that was executed revealed that the pavement of the old road had not been removed, whereas layers of sandy gravel and loose sand were laid above the road’s asphalt pavement which eventually acted as conduits allowing se¬lective flow of water under the runway pave¬ment. The paper presents the site investigation (including the extensive desk study required to identify the possible origins of the problem), the geotechnical findings, lab test results and the engineering solution applied for the reha¬bi¬litation of the pavement at an area where the combined effect of aircraft loading and poor sub¬grade, becoming even poorer during pro¬longed seepage causing fines’ movement, led to persistent pavement distresses.

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Research paper thumbnail of THE LIGHT DYNAMIC PENETROMETER AND ITS USE IN GEOTECHNICAL INVESTIGATION FOR PAVEMENTS AND OTHER WORKS (in Greek)

HSSMGE one-day conference on Geotechnical Engineering and Pavement Design, 2022

The Dynamic Cone Penetration-Light test (DCP) is widely used for the determination of soil streng... more The Dynamic Cone Penetration-Light test (DCP) is widely used for the determination of soil strength in-situ and the compaction control of pavement layers. It is used for geotechnical investigation of road and highway works, for soil classification, for stratigraphy determination and for earthworks’ construction quality control. The results of the test are correlated to SPT and other geotechnical properties, such as CBR, modulus of elasticity or resi¬lient modulus, stiffness modulus, unconfined compressive strength, relative density etc. This test however can, with limited modifications, serve in geotechnical investigation mostly thanks to the ease of transport and access of the equipment, the ability to perform the test faster than other means of site investigation and the fact that it does not need specialised personnel to perform the test. It is also very useful, even for investigation to considerable depth, not so much in this case for estimation of parameters by empirical relations, as for the reconnaissance of stratigraphy, especially when other methods cannot be applied due to time, space or cost restrictions.

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Research paper thumbnail of SOIL MECHANICS TESTS AND CLASSIFICATION SYSTEMS OF THE PAVEMENTS’ FOUNDATION LAYER (in Greek)

HSSMGE one-day conference on Geotechnical Engineering and Pavement Design, 2022

The foundation layer is the natural subgrade or man-made layer, on which the pavement is construc... more The foundation layer is the natural subgrade or man-made layer, on which the pavement is constructed. The physical and mechanical properties of the foundation layer affect the overall pavement behaviour and have significant impact on the dimensioning of the base/subbase layers and the surface layers of Hot Mix Asphalt concrete (HMA) or Portland Cement Concrete (PCC). The existing Hellenic Technical Specifications (ΕΛΟΤ ΤΠ) provide guidance on the laboratory and insitu tests required for the acceptance of natural or borrow material, the quality assurance compliance during construction and the compaction of the foundation layer.

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Research paper thumbnail of A large-scale drainage field array to establish the effect of vertical drainage wells on underdrainage pore pressure profiles as part of a landslide stabilization scheme

11th Intnl Symp on Field Monitoring in Geomechanics, 2022

The paper presents results from a large-scale field array of vertical drainage wells penetrating ... more The paper presents results from a large-scale field array of vertical drainage wells penetrating the landslide material of a large palaeolandslide in Greece overlying a buried river bed. Piezometers with Casagrande type tips were installed before drilling the wells. Monitoring of pore pressures in these piezometers allowed the measurement of the pore pressure regime in the landslide material before drilling the wells and the actual effect of the wells on this regime after they were drilled. The initial pore pressure profile established corresponded to underdrainage. The monitoring results after drilling the wells indicated considerable decrease of pore pressure in the landslide materials downstream of the wells and some decrease upstream of the wells.

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Research paper thumbnail of Examples of mechanical properties and slope instabilities in expansive soils in Cyprus

WORKSHOP on THE GEOTECHNICAL CHALLENGES POSED BY HIGH PLASTICITY CLAYS, 2022

An invited lecture delivered at the Univeristy of Cyprus in Nicosia as part of the WORKSHOP on TH... more An invited lecture delivered at the Univeristy of Cyprus in Nicosia as part of the WORKSHOP on THE GEOTECHNICAL CHALLENGES POSED BY HIGH PLASTICITY CLAYS on the 11th of July 2022.

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Research paper thumbnail of Long-term suction measurements in Greece & Cyprus. A continuous update

4th European Conference on Unsaturated Soils (E-UNSAT 2020), 2020

The occurrence of unsaturated soils in the field has been well documented worldwide by measuremen... more The occurrence of unsaturated soils in the field has been well documented worldwide by measurements of the degree of saturation on samples taken during geotechnical investigations. On the other hand, the suction of unsaturated soils in the field, especially as part of long-term measurements, is documented very rarely and references on the subject are very few and for very few places around the world. The scarceness of this kind of measurements denies researchers perception of the anticipated suction and its possible loss or retention as a result of climatic conditions, especially in countries with warm temperate climate. Suction measurements from temporary and permanent stations in Greece and Cyprus are presented in the paper. From these-admittedly few-measurements until today, the large magnitude of suction that may occur both during summer and winter is presented, along with the possibility of long periods of these suctions being maintained. Another consequence is the range of suction values that sensors should be able to measure in regions of similar climatic conditions in order to cover the range of expected values as obtained from the measurements available so far.

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Research paper thumbnail of Slope stability and landslides in the climatic and developing conditions of Greece and Cyprus (in Greek)

University of Cyprus Seminar Series: The engineer in society, 2020

An invited lecture on slope stability and landslides delivered at the University of Cyprus in Nic... more An invited lecture on slope stability and landslides delivered at the University of Cyprus in Nicosia on the 20th February 2020. The lecture goes through basic slope stability and landslide analysis based on the limit equilibrium method with comments on particular points of interest or caution from examples of real landslides investigated, analysed and stabilised. Starting from general considerations, the lecture then focuses on the effect of the climatic conditions in Greece and Cyprus on the mechanical behaviour of soils near the ground surface (unsaturated soils, their behaviour and the effect of changes in partial saturation) and the consequences of increasing building activity related to tourism with examples from Cyprus.

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Research paper thumbnail of Simulation of mat bending due to changes in moisture in the foundation soil (in Greek)

8th Hellenic Conference on Geotechnical Engineering, 2019

Swelling soils develop volumetric strains during wetting or drying that result in damages to stru... more Swelling soils develop volumetric strains during wetting or drying that result in damages to structures founded in them. This article presents a simple constitutive model meant to be used in coupled finite element analyses of soil-mat foundation interaction due to moisture content fluctuations. This model is a combination of a non-linear elastic law and a mechanism that predicts volumetric strains caused by changes in suction. Analyses show that the deformations caused by moisture migration from and towards the peripheral zone of a mat foundation can generate significant bending moments, which must not be neglected in the foundation design.

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Research paper thumbnail of Evaluation of Existing Airport Pavement Aggregate and Subgrade Layers (in Greek)

8th Hellenic Conference on Getoechnical Engineering , 2019

Assessment of the present condition and the mechanical parameters of the ag-gregate and subgrade ... more Assessment of the present condition and the mechanical parameters of the ag-gregate and subgrade layers may be highly important or even critical for the optimization of the existing pavement rehabilitation design. The present paper focuses on the procedure used for the investigation of aggregate and unbound layers at Kos airport, which is a typical example of existing old pavement that suffers from extensive surface distress and local failures.

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Research paper thumbnail of The light dynamic penetrometer test and its use (in Greek)

Proceedings 8th Hellenic Conference on Geotechnical Engineering, 2019

The Dynamic Cone Penetration-Light test (DCP) is widely used for the determination of soil streng... more The Dynamic Cone Penetration-Light test (DCP) is widely used for the determination of soil strength in-situ and the compaction control of pavement layers. It is used for geotechnical investigation of road and highway works, for soil classification, for stratigraphy determination and for earthworks’ construction quality control. The results of the test are correlated to SPT and other geotechnical properties, such as CBR, modulus of elasticity or resilient modulus, stiffness modulus, unconfined compressive strength, relative density etc.

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Research paper thumbnail of Mechanical behavior of compacted chalk from Tersephanou, Cyprus (in Greek)

Proceedings 8th Hellenic Conference on Geotechnical Engineering, 2019

Laboratory test results on compacted chalk from Tersephanou Cyprus are presented in the paper. Th... more Laboratory test results on compacted chalk from Tersephanou Cyprus are presented in the paper. The tests were performed in a large-size direct shear device with circular section. The particular chalk in-situ constitutes a rock mass of poor to medium quality which upon contact with water or mechanical straining, like that induced by compaction, yields a material of soil-like behaviour. The shear strength, volume changes and coefficient of earth pressure at rest and its evolution with vertical stress and unloading-reloading cycles were measured and are presented in the paper.

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Research paper thumbnail of Long-term measurements of suction in the field (in Greek)

Proceedings 8th Hellenic Conference on Geotechnical Engineering, 2019

The suction of unsaturated soils in the field, especially during long-term monitoring, is measure... more The suction of unsaturated soils in the field, especially during long-term monitoring, is measured rarely. The lack of measurements of this kind denies geotechnical engineers the experience of the magnitude that this property may obtain in countries with climate like that of Greece and Cyprus, as well as the experience of retention or loss of this suction due to climatic conditions. Suction measurements from stations in Greece and Cyprus are presented in the article. These measurements document the large magnitude that suction may obtain during both summer and even winter, as well as its retention for very long periods.

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Research paper thumbnail of Long-term monitoring and behaviour of mudbricks and small mudbrick walls (in Greek)

9th Hellenic Conference on Geotechnical Engineering, 2023

The drying of full-size mudbricks and small mudbrick walls was investigated for various hay conte... more The drying of full-size mudbricks and small mudbrick walls was investigated for various hay contents by monitoring suction and volumetric water content as these were measured on sensors installed inside mudbricks and mudbrick walls. A higher drying rate is observed with increasing hay content. Mudbrick walls exhibit smaller uniaxial compressive strength compared to cubes sized 10x10x10cm. As the the size of mudbricks is increased, a tendency for uniaxial compressive strength with the increase of the wall size is observed.

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Research paper thumbnail of Investigation of index and mechanical properties of mudbricks from the ancient walls of Eleusis (in Greek)

9th Hellenic Conference on Geotechnical Engineering, 2023

Samples of ancient mudbricks from the remnants of the ancient walls of the Eleusis Sanctuary were... more Samples of ancient mudbricks from the remnants of the ancient walls of the Eleusis Sanctuary were tested. Their index and mechanical properties were measured and on the basis of these results, soil material from the archaeological site with the same properties was identified. This was subjected to compaction with various compaction energies per volume and hay content that allowed the determination of a suitable compaction energy per volume and hay content leading to the reproduction of new mudbricks with properties as close as possible to the ancient ones.

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Research paper thumbnail of Moisture Migration Under Mat Foundations in Nicosia Marl

Geotechnical and Geological Engineering, 2018

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Research paper thumbnail of A simplified approach to estimating the evolution of residual shear strength of unsaturated soils with suction

E3S Web of Conferences, 2023

Several researchers have investigated the effect of suction and partial saturation on the angle o... more Several researchers have investigated the effect of suction and partial saturation on the angle of residual shear strength. Most of these investigations involve the adoption and application of a method of controlling suction on the ring shear apparatus and performing ring shear tests on the same soil for various values of suction. Methods adopted include both the axis translation technique for control of suction over the range 50-1500 kPa and the saturated salt solutions method for control of suction in the range of several MPa. The general picture from these investigations is that the residual shear strength failure envelope remains linear but corresponding to higher values of the angle of residual shearing resistance for constant suction; this value increasing with increasing suction. The paper presents an attempt to normalise values of measured angle of residual shearing resistance for various suction values with the angle of residual shear strength of the corresponding fully saturated soil. This normalisation verified the linear increase of the ratio tanφres(s)/tanφres(s=0) with suction. This linear increase allows for estimation of the evolution of tanφres(s) with suction if φres(s) for one specific suction can be measured. This observation led to the measurement of tanφres(s) of clayey soils in conventional ring shear apparatus without suction control, simply by removing water from the shear box while shearing continues and measuring shear strength until its stabilisation, taking place after the specimen in the shear box came to equilibrium with prevailing laboratory atmospheric conditions. Using the chilled mirror hygrometer to measure equilibrium suction after ring shear completion indicated that equilibrium suction due to laboratory atmospheric conditions is practically constant over the time needed for a single test on one soil. This observation along with the previous observation on the linear increase of the ratio tanφres(s)/tanφres(s=0) with suction, makes valid the estimation of evolution of residual shear strength of unsaturated soils with suction using only a conventional ring shear apparatus and a chilled mirror hygrometer. The paper concludes by outlining the approach, presenting measurements and a relation obtained between tanφres(s)/tanφres(s=0), suction and liquid limit.

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Research paper thumbnail of Investigation of the properties and behaviour of ancient and newly constructed mudbricks from the ancient walls of Eleusis

E3S Web of Conferences, 2023

The paper presents the test results from the investigation of the nature and mechanical behaviour... more The paper presents the test results from the investigation of the nature and mechanical behaviour of mudbricks from the ancient mudbrick wall of Eleusis in Attica, Greece. The mudbrick wall remains preserved to date in the site of Eleusis are some of the largest preserved in Greece. Small fragments of mudbricks were taken to the laboratory for experimental investigation. Testing included index tests to classify the soil material the mudbricks were made of, mineralogical analyses of their fines' content, mechanical testing suitable for the nature of the materials and the ability to trim the samples without causing damage and measurements of suction on samples as they were obtained, further dried, or rewetted. The soil material used for ancient mudbrick construction was a silty sand to sandy silt with a small fraction clay content, with marginally plastic to non-plastic fines. Dry unit weight was found to be close to the dry unit weight of fresh mudbrick material after being compacted with a minimum compaction energy of only 45 kNm/m 3 and left to dry to residual water content conditions. Similarly, field water content was found close to the residual water content of these recompacted soil samples. Consequently, unconfined compression strength was found very high corresponding to the residual water content condition, with similarly high cohesion obtained from direct shear tests and a very high yield stress under one-dimensional conditions of loading.

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Research paper thumbnail of A simplified approach to estimating the evolution of residual shear strength of unsaturated soils with suction

E3S Web of Conferences

Several researchers have investigated the effect of suction and partial saturation on the angle o... more Several researchers have investigated the effect of suction and partial saturation on the angle of residual shear strength. Most of these investigations involve the adoption and application of a method of controlling suction on the ring shear apparatus and performing ring shear tests on the same soil for various values of suction. Methods adopted include both the axis translation technique for control of suction over the range 50-1500 kPa and the saturated salt solutions method for control of suction in the range of several MPa. The general picture from these investigations is that the residual shear strength failure envelope remains linear but corresponding to higher values of the angle of residual shearing resistance for constant suction; this value increasing with increasing suction. The paper presents an attempt to normalise values of measured angle of residual shearing resistance for various suction values with the angle of residual shear strength of the corresponding fully sat...

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Research paper thumbnail of Reproduction and long-term monitoring of drying of mudbricks and small mudbrick walls for the preservation of the ancient mudbrick wall of Eleusis

E3S Web of Conferences

The mudbrick wall remains preserved to date in the site of Eleusis are some of the largest preser... more The mudbrick wall remains preserved to date in the site of Eleusis are some of the largest preserved in Greece. Following an extensive investigation of the properties of existing mudbricks, material of similar properties from the archaeological site of Eleusis was used to reproduce mudbricks of similardensity with the ancient ones after drying with various concentrations of dry grass also from the archaeological site. Actual mudbricks were reproduced and brought to a final equilibrium condition under climatic conditions practically similar to those in Eleusis. Others were used to trim samples and measuremechanical properties to compare with original mudbricks, others were instrumented with suction and volumetric water content sensors in order to monitor mudbrick drying under climatic conditions and others in order to build small mudbrick walls with mortar from the same soil used to make the mudbricks. These small mudbrick walls included the mudbricks with internally installed suctio...

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Research paper thumbnail of Some examples and lessons from long-term field measurements of suction in Greece

E3S Web of Conferences

The occurrence of unsaturated soils in the field has been well documented worldwide by measuremen... more The occurrence of unsaturated soils in the field has been well documented worldwide by measurements of the degree of saturation on samples taken during geotechnical investigations. On the other hand, the suction of unsaturated soils in the field, especially as part of long-term measurements, is documented very rarely and references on the subject are very few and for very few places around the world. The scarceness of this kind of measurements denies researchers perception of the anticipated suction and its possible loss, or retention, as a result of climatic conditions, especially in countries with warm temperate climate. Suction measurements from temporary and permanent stations in Greece and Cyprus have been presented in the past showing that considerably high values of suction can develop and be maintained even during wet periods. This paper focuses on examples and lesson learned from stations in Greece, especially magnitude and change of suction with time, as well as longevity ...

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Research paper thumbnail of ROADS UNDER AIRPORTS: A CASE STUDY FROM INTERNATIONAL AIRPORT “DIAGORAS” ON RHODES ISLAND AND ITS LABORATORY AND FIELD INVESTIGATION (in Greek)

HSSMGE one-day conference on Geotechnical Engineering and Pavement Design, 2022

Runway 07-25 of “Diagoras” Inter¬national Airport on Rhodes island in Greece was suffering persis... more Runway 07-25 of “Diagoras” Inter¬national Airport on Rhodes island in Greece was suffering persistent pavement distresses at ch. 1+395. Surface depressions were very regularly recorded at approximately 3.5m to the left and right of the axis of the runway, with rapidly evolving extent during periods of heavy aircraft traffic or after heavy rainfall incidents follow¬ing prolonged dry periods. Satellite images and airport maintenance log reviews revealed that these distresses appeared systematically at the sa¬me location very soon, even after every superficial rehabilitation of the pavement. The desk study carried out during the recon¬nais¬sance phase of the problem revealed that the problematic pavement section coincides with the alignment of an old road that existed prior to airport construction. This road which used to connect the nearby Paradeisi village with the seashore seemed to remain a direct buried con¬duit for subsurface drainage towards the sea, as also revealed from the outflow location of fire-fighting vehicles’ foam after an aviation safety incident that happened near the problematic pavement area. A thorough geotechnical inve¬sti¬gation that was executed revealed that the pavement of the old road had not been removed, whereas layers of sandy gravel and loose sand were laid above the road’s asphalt pavement which eventually acted as conduits allowing se¬lective flow of water under the runway pave¬ment. The paper presents the site investigation (including the extensive desk study required to identify the possible origins of the problem), the geotechnical findings, lab test results and the engineering solution applied for the reha¬bi¬litation of the pavement at an area where the combined effect of aircraft loading and poor sub¬grade, becoming even poorer during pro¬longed seepage causing fines’ movement, led to persistent pavement distresses.

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Research paper thumbnail of THE LIGHT DYNAMIC PENETROMETER AND ITS USE IN GEOTECHNICAL INVESTIGATION FOR PAVEMENTS AND OTHER WORKS (in Greek)

HSSMGE one-day conference on Geotechnical Engineering and Pavement Design, 2022

The Dynamic Cone Penetration-Light test (DCP) is widely used for the determination of soil streng... more The Dynamic Cone Penetration-Light test (DCP) is widely used for the determination of soil strength in-situ and the compaction control of pavement layers. It is used for geotechnical investigation of road and highway works, for soil classification, for stratigraphy determination and for earthworks’ construction quality control. The results of the test are correlated to SPT and other geotechnical properties, such as CBR, modulus of elasticity or resi¬lient modulus, stiffness modulus, unconfined compressive strength, relative density etc. This test however can, with limited modifications, serve in geotechnical investigation mostly thanks to the ease of transport and access of the equipment, the ability to perform the test faster than other means of site investigation and the fact that it does not need specialised personnel to perform the test. It is also very useful, even for investigation to considerable depth, not so much in this case for estimation of parameters by empirical relations, as for the reconnaissance of stratigraphy, especially when other methods cannot be applied due to time, space or cost restrictions.

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Research paper thumbnail of SOIL MECHANICS TESTS AND CLASSIFICATION SYSTEMS OF THE PAVEMENTS’ FOUNDATION LAYER (in Greek)

HSSMGE one-day conference on Geotechnical Engineering and Pavement Design, 2022

The foundation layer is the natural subgrade or man-made layer, on which the pavement is construc... more The foundation layer is the natural subgrade or man-made layer, on which the pavement is constructed. The physical and mechanical properties of the foundation layer affect the overall pavement behaviour and have significant impact on the dimensioning of the base/subbase layers and the surface layers of Hot Mix Asphalt concrete (HMA) or Portland Cement Concrete (PCC). The existing Hellenic Technical Specifications (ΕΛΟΤ ΤΠ) provide guidance on the laboratory and insitu tests required for the acceptance of natural or borrow material, the quality assurance compliance during construction and the compaction of the foundation layer.

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Research paper thumbnail of A large-scale drainage field array to establish the effect of vertical drainage wells on underdrainage pore pressure profiles as part of a landslide stabilization scheme

11th Intnl Symp on Field Monitoring in Geomechanics, 2022

The paper presents results from a large-scale field array of vertical drainage wells penetrating ... more The paper presents results from a large-scale field array of vertical drainage wells penetrating the landslide material of a large palaeolandslide in Greece overlying a buried river bed. Piezometers with Casagrande type tips were installed before drilling the wells. Monitoring of pore pressures in these piezometers allowed the measurement of the pore pressure regime in the landslide material before drilling the wells and the actual effect of the wells on this regime after they were drilled. The initial pore pressure profile established corresponded to underdrainage. The monitoring results after drilling the wells indicated considerable decrease of pore pressure in the landslide materials downstream of the wells and some decrease upstream of the wells.

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Research paper thumbnail of Examples of mechanical properties and slope instabilities in expansive soils in Cyprus

WORKSHOP on THE GEOTECHNICAL CHALLENGES POSED BY HIGH PLASTICITY CLAYS, 2022

An invited lecture delivered at the Univeristy of Cyprus in Nicosia as part of the WORKSHOP on TH... more An invited lecture delivered at the Univeristy of Cyprus in Nicosia as part of the WORKSHOP on THE GEOTECHNICAL CHALLENGES POSED BY HIGH PLASTICITY CLAYS on the 11th of July 2022.

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Research paper thumbnail of Long-term suction measurements in Greece & Cyprus. A continuous update

4th European Conference on Unsaturated Soils (E-UNSAT 2020), 2020

The occurrence of unsaturated soils in the field has been well documented worldwide by measuremen... more The occurrence of unsaturated soils in the field has been well documented worldwide by measurements of the degree of saturation on samples taken during geotechnical investigations. On the other hand, the suction of unsaturated soils in the field, especially as part of long-term measurements, is documented very rarely and references on the subject are very few and for very few places around the world. The scarceness of this kind of measurements denies researchers perception of the anticipated suction and its possible loss or retention as a result of climatic conditions, especially in countries with warm temperate climate. Suction measurements from temporary and permanent stations in Greece and Cyprus are presented in the paper. From these-admittedly few-measurements until today, the large magnitude of suction that may occur both during summer and winter is presented, along with the possibility of long periods of these suctions being maintained. Another consequence is the range of suction values that sensors should be able to measure in regions of similar climatic conditions in order to cover the range of expected values as obtained from the measurements available so far.

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Research paper thumbnail of Slope stability and landslides in the climatic and developing conditions of Greece and Cyprus (in Greek)

University of Cyprus Seminar Series: The engineer in society, 2020

An invited lecture on slope stability and landslides delivered at the University of Cyprus in Nic... more An invited lecture on slope stability and landslides delivered at the University of Cyprus in Nicosia on the 20th February 2020. The lecture goes through basic slope stability and landslide analysis based on the limit equilibrium method with comments on particular points of interest or caution from examples of real landslides investigated, analysed and stabilised. Starting from general considerations, the lecture then focuses on the effect of the climatic conditions in Greece and Cyprus on the mechanical behaviour of soils near the ground surface (unsaturated soils, their behaviour and the effect of changes in partial saturation) and the consequences of increasing building activity related to tourism with examples from Cyprus.

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Research paper thumbnail of Simulation of mat bending due to changes in moisture in the foundation soil (in Greek)

8th Hellenic Conference on Geotechnical Engineering, 2019

Swelling soils develop volumetric strains during wetting or drying that result in damages to stru... more Swelling soils develop volumetric strains during wetting or drying that result in damages to structures founded in them. This article presents a simple constitutive model meant to be used in coupled finite element analyses of soil-mat foundation interaction due to moisture content fluctuations. This model is a combination of a non-linear elastic law and a mechanism that predicts volumetric strains caused by changes in suction. Analyses show that the deformations caused by moisture migration from and towards the peripheral zone of a mat foundation can generate significant bending moments, which must not be neglected in the foundation design.

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Research paper thumbnail of Evaluation of Existing Airport Pavement Aggregate and Subgrade Layers (in Greek)

8th Hellenic Conference on Getoechnical Engineering , 2019

Assessment of the present condition and the mechanical parameters of the ag-gregate and subgrade ... more Assessment of the present condition and the mechanical parameters of the ag-gregate and subgrade layers may be highly important or even critical for the optimization of the existing pavement rehabilitation design. The present paper focuses on the procedure used for the investigation of aggregate and unbound layers at Kos airport, which is a typical example of existing old pavement that suffers from extensive surface distress and local failures.

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Research paper thumbnail of The light dynamic penetrometer test and its use (in Greek)

Proceedings 8th Hellenic Conference on Geotechnical Engineering, 2019

The Dynamic Cone Penetration-Light test (DCP) is widely used for the determination of soil streng... more The Dynamic Cone Penetration-Light test (DCP) is widely used for the determination of soil strength in-situ and the compaction control of pavement layers. It is used for geotechnical investigation of road and highway works, for soil classification, for stratigraphy determination and for earthworks’ construction quality control. The results of the test are correlated to SPT and other geotechnical properties, such as CBR, modulus of elasticity or resilient modulus, stiffness modulus, unconfined compressive strength, relative density etc.

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Research paper thumbnail of Mechanical behavior of compacted chalk from Tersephanou, Cyprus (in Greek)

Proceedings 8th Hellenic Conference on Geotechnical Engineering, 2019

Laboratory test results on compacted chalk from Tersephanou Cyprus are presented in the paper. Th... more Laboratory test results on compacted chalk from Tersephanou Cyprus are presented in the paper. The tests were performed in a large-size direct shear device with circular section. The particular chalk in-situ constitutes a rock mass of poor to medium quality which upon contact with water or mechanical straining, like that induced by compaction, yields a material of soil-like behaviour. The shear strength, volume changes and coefficient of earth pressure at rest and its evolution with vertical stress and unloading-reloading cycles were measured and are presented in the paper.

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Research paper thumbnail of Long-term measurements of suction in the field (in Greek)

Proceedings 8th Hellenic Conference on Geotechnical Engineering, 2019

The suction of unsaturated soils in the field, especially during long-term monitoring, is measure... more The suction of unsaturated soils in the field, especially during long-term monitoring, is measured rarely. The lack of measurements of this kind denies geotechnical engineers the experience of the magnitude that this property may obtain in countries with climate like that of Greece and Cyprus, as well as the experience of retention or loss of this suction due to climatic conditions. Suction measurements from stations in Greece and Cyprus are presented in the article. These measurements document the large magnitude that suction may obtain during both summer and even winter, as well as its retention for very long periods.

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Research paper thumbnail of The landslides of Sesklo Clay Mine in central Greece. Designing to save an archaeological site and maintain mine operations.

ICONHIC 2022, 2022

The Sesklo open-pit clay mine is located near the city of Volos in central Greece. It is one of t... more The Sesklo open-pit clay mine is located near the city of Volos in central Greece. It is one of the oldest clay mines still in operation in Greece and the clay mined is used for cement production. The highest slopes in the mine are 80m high. Between 1999 and 2000 three major slides occured in the mine. One was a deep-seated landslide with base failure putting potentially in danger the ruins of a prehistoric settlement with important archaeological findings. It was 250m long, 250m wide with an estimated maximum depth of 65-70m. Two more landslides that occurred were smaller; one 100m long and 100m wide with a maximum depth of 18m, and the other 150m long, 150m wide with a maximum depth of 35m. The geometry of all landslides was dictated by a combination of the anisotropy of the clay formations, the existence of layers of very poor characteristics, and the magnitude and geometry of excavations during operation. The paper presents the results of the geotechnical investigation performed, the slope stability analyses performed in order to redesign the clay mine slopes geometry and ensure long-lasting affordable operation, while at the same time ensuring the safety required for the prehistoric settlement, especially given the high seismicity of the area.

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Research paper thumbnail of A landslide in bentonitic clays in Pafos, Cyprus

EUROENGEO 3rd European Regional Conference of IAEG, 2021

Paphos region in west Cyprus is a region notorious for its landslide susceptibility. Bentonitic c... more Paphos region in west Cyprus is a region notorious for its landslide susceptibility. Bentonitic clays of very high plasticity are found from the ground surface to considerable depth. These materials have very low peak and residual shear strength with angles of residual shear strength as low as 6-7o. Combining this very low strength with high precipitation dictated by the Mediterranean Sea to the west of the region leads to frequent slope stability problems even in very mild slopes.
The paper presents one such case near Armou village close to the city of Paphos. The landslide is approximately 300m long and 150m wide affecting a number of properties close to the crest. The average slope angle toe to crest is 7o. The landslide’s lateral boundaries are streams eroding its sides and contributing to the pore pressure regime in the landslide mass. Pore pressure increase and duration is aggravated by local small earth dams created for agricultural purposes on these streams. The landslide is a combination of circular and translational landslide with evidence indicating it is retrogressive in nature. Marine terrace layers lie above the bentonitic clays and are currently found turned due to rotation of the lowest part before the upstream one followed and so forth. Adding to this, between autumn 2018 and spring 2020 the crest of the landslide has advanced further upstream in a fashion similar to that found in the downstream parts of the landslide. Evident accumulated movements of the landslide mass make it a palaeolandslide with the material along the sliding surface having strength practically close to residual.
Due to the proximity of the area to Neapolis University, Paphos, the landslide serves as the subject of a site visit for the students of Engineering Geology and Soil Mechanics of the university. During these visits surface samples from around the landslide were collected and tested. These tests indicate the presence of a bentonitic clay with liquid limit in the order of 120-130% and a plasticity index of 100%. Peak shear strength values correspond to cohesion between 10 and 20 kPa and an angle of shearing resistance in the order of 20o, while the angle of residual shear strength ranges between 6 and 10o. Topographical data were collected from the Land Registy and Mapping Department of Cyprus and longitudinal and lateral sections were drafted in order to carry out slope stability back analyses using the limit equilibrium method. Pore pressures were modelled using the pore pressure coefficient ru, and values were sought after so that the angle of residual shear strength from the back analyses was 1-2o higher than those obtained in the laboratory tests. Sliding surfaces along the longitudinal sections were cross-checked so as they correspond to a convex surface from their depths plotted along the lateral sections.
This work is presented in the paper as an initial study of the Armou landslide contributing to the geological and engineering identification and classification of this landslide and serving even further to the educational material provided to the students of Neapolis University during their site visits to the area.

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