A Review of Direct Shear and Inclined Plane Tests Results for Different Interfaces in Landfill Capping (original) (raw)
Related papers
International Journal of Geosynthetics and Ground Engineering
Landfill liners are critical components of waste containment systems that are designed to prevent the migration of pollutants into the environment. Accurate measurement of the shear strength of soil–geosynthetic and geosynthetic–geosynthetic interfaces is essential for designing safe and cost-effective landfill liners. This paper presents a comparative study of the shear strength parameters of single and multi-layer interfaces using a Large Direct Shear Apparatus (LDSA). The study aimed to investigate the effects of using different testing configurations on the Peak and Large Displacement (LD) strengths of the interfaces and to identify the test configuration that provides the most critical shear strength results. A “305 × 305 mm” LDSA was used to perform interface shear tests in saturated conditions with applied normal stresses ranging from 50 to 400 kPa. The results showed good agreement between strength envelopes derived from single and multi-layer interface tests for the materia...
Large-Scale Shear Tests on Interface Shear Performance of Landfill Liner Systems
Geosynthetics in Civil and Environmental Engineering
Interface shear performance of various landfill liner systems were evaluated for landfill stability by conducting large scale shear tests. Testing program covers the interfaces between (1) geosynthetics (geomembrane (GM) sheet (HDPE and PVC) and non-woven geotextile) and subsoil, (2) geosynthetics and compacted clay liner (CCL), and (3) GM and geotextile. The focus of this paper is placed on interface shear performance under both as installed condition (dry for geosynthetics and optimum moisture content for CCL or subsoil) and saturated / wet condition, since landfill liner system is often subjected to saturated / wet condition due to the higher water retention capacity of CCL as well as the contact to leachate and/or groundwater. For geotextile-GM interface, there is no significant effect on the interface shear strength. The saturated CCL-GM interface had lower shear strength compared to the interface under as installed condition, although the shear performances of CCL-geotextile interface under both conditions are similar to each other. For the interfaces between geosynthetics and subsoil, the frictional resistance of HDPE with textures surface had a significant drop from 23 to 15 degree in the saturated / wet condition.
Interface shear strength variability and its use in reliability-based landfill stability analysis
Geosynthetics International, 2006
Failure of modern landfills by slippage of lining materials and waste bodies is not uncommon. The majority of failures are controlled by slippage at interfaces between lining components. Information on variability of interface shear strength is required both to carry out limit equilibrium stability analysis using characteristic shear strengths and to analyse the probability of failure. Current practice is to carry out a limited number of site-specific tests, and this provides insufficient information on the variability of interface strength for design. A summary of measured strengths and an assessment of variability are presented for seven generic interfaces common in landfill lining systems. This combines values from the international literature, from an internal database, and from the results of repeatability testing programmes. The implications of variable shear strength are examined though failure probability analysis for two common design casesveneer and waste body slippage -and this adds to the small number of studies published previously. The reliability analyses show that relatively high probabilities of failure are obtained when using variability values from the literature and an internal database, even when factors of safety > 1.5. The use of repeatability data produces lower probabilities for typically used factors of safety, although they are still higher than recommended target probability of failure values.
Interface shear strength of geosynthetics: Evaluation and analysis of inclined plane tests
Geotextiles and Geomembranes, 2009
The inclined plane test (IPT) is commonly performed to measure the interface shear strength between different materials as those used in cover systems of landfills. The test, when interpreted according to European test Standards provides the static interface friction angle, usually assumed for 50 mm displacement and denoted as f stat 50 . However, if interpreted considering the several phases of the sliding process, the test is capable of yielding more realistic information about the interface shear strength such as differentiating interfaces which exhibit the same value of f stat 50 but different behavior for displacement less than 50 mm. In this paper, the IPT is used to evaluate the interface shear strength of some materials usually present in cover liner systems of landfill. The results of the tests were analyzed for both, the static and the dynamic phases of the sliding and were interpreted based on the static initial friction angle, f 0 , and the limit friction angle, f lim . It is shown that depending on the sliding behavior of the interfaces, f stat 50 , which is usually adopted as the designing parameter in stability analysis, can be larger than f 0 and f lim .
E3S Web of Conferences
The design of a competent basal lining system is crucial in ensuring a long-lasting and functional engineered municipal solid waste (MSW) landfill. However, due to the inclusion of numerous geosynthetics and geomaterials forming a multi-layered lining system, there rises an uncertainty on determining the critical or weakest interface. This is exacerbated by the different properties offered by these lining materials and their inter-crossing functions in landfills. According to ASTM D5321-20 standard, the interface shear strengths used in design of bases and side-slopes of lining systems are determined through a single interface testing configuration. However, minimal research has been done to evaluate the consequences of multi-interface testing configurations on the minimum factors of safety (FoSmin). The present study was thus conducted to further investigate this phenomena while establishing the appropriateness of double interface testing configuration using large direct shear equi...
Studia Geotechnica et Mechanica, 2013
The problem of managing the unneeded and unusable materials is a serious challenge for modern societies. The progress of civilization is accompanied by an increase of the human population. This results in a constant increase of waste production. An average EU citizen generates over 500 kg of municipal waste per year, of which less than one third is recycled. The rest is either disposed of in the landfills or incinerated. Every landfill needs to be properly protected by an impermeable barrier - a liner. Its use is necessary to prevent soil and ground water contamination. The protection barrier needs to be implemented both at the bottom and at the top of a landfill. Various geosynthetic materials are utilized for a liner design. Waste disposed of in a landfill creates high embankments with steep slopes. In these conditions, the problem of liner stability arises. The tests, the results of which are presented in this paper, were conducted to analyze the behaviour of several different co...
Dynamic Shear Degradation of Geosynthetic–Soil Interface in Waste Landfill Sites
Applied Sciences, 2017
Geosynthetics and soil particles inevitably come into contact, resulting in a geosynthetic-soil interface. The discontinuity of the materials at the interface causes an intricate shear response, especially under dynamic loads. In the present study, the effects of chemical aggressors of the leachate from a waste landfill site on the cyclic shear behaviors of a geosynthetic-soil interface were investigated. The MultiPurpose Interface Apparatus (M-PIA) that can simulate cyclic simple shear conditions was utilized, and 72 sets of cyclic simple shear tests were conducted. The Disturbed State Concept (DSC) was employed to quantitatively estimate the shear stress degradation. As a result, new disturbance functions and parameters that represent the characteristics of the dynamic shear degradation at the interface were evaluated. Additionally, a numerical back-prediction was performed to verify the accuracy and applicability of the DSC parameters. Numerical interpolation procedures were suggested and enabled to reproduce the degradation successfully. Consequently, a general methodology was established to estimate the cyclic shear stress degradation of the geosynthetic-soil interface in consideration of chemical effects.
Influence of Surface Texture on the Interface Shear Capacity of Landfill Liner
Geomembrane is one of the most widely used geosynthetics in various civil engineering applications. Its primary function is to act as a barrier for liquid and/or vapour. Smooth geomembrane is frequently used in combination with different soils, and however due to its low surface roughness, the main concern in the design is to ensure adequate shear capacity along the smooth geomembrane/soil interface. The use of smooth geomembrane will lead to low interface shear capacity between landfill liner components which can be considered as one of the major factors in the landfill slope stability failures. Modification of HDPE geomembrane from smooth surface to textured surface is therefore required to improve interface shear capacity of landfill liners. In this study, several interfaces of landfill liner components were tested by using large scale shear box. The combinations used were (1) Sand:Bentonite (100:5)/Smooth HDPE; (2) Sand:Bentonite (100:10)/Smooth HDPE; (3) Sand:Bentonite (100:5)/...
Stability performance and interface shear strength of geocomposite drain/soil systems
AIP Conference Proceedings, 2018
Landfill covers are designed as impermeable caps on top of waste containment facilities after the completion of landfill operations. Geocomposite drain (GD) materials consist of a geonet or geospacer (as a drainage core) sandwiched between non-woven geotextiles that act as separators and filters. GD provides a drainage function as part of the cover system. The stability performance of landfill cover system is largely controlled by the interface shear strength mobilized between the elements of the cover. If a GD is used, the interface shear strength properties between the upper surface of the GD and the overlying soil may govern stability of the system. It is not uncommon for fine grained materials to be used as cover soils. In these cases, understanding soil softening issues at the soil interface with the non-woven geotextile is important. Such softening can be caused by capillary break behaviour and build-up of water pressures from the toe of the drain upwards into the cover soil. The interaction processes to allow water flow into a GD core through the soil-geotextile interface is very complex. This paper reports the main behaviour of in-situ interface shear strength of soil-GD using field measurements on the trial landfill cover at Bletchley, UK. The soil softening at the interface due to soaked behaviour show a reduction in interface shear strength and this aspect should be emphasized in design specifications and construction control. The results also help to increase confidence in the understanding of the implications for design of cover systems.
Comparison of Single and Multi Geosynthetic and Soil Interface Tests
2012
This paper presents a comparison of single-and multi-interface strength tests for two possible landfill liner system configurations. The paper provides a comparison of the peak and large displacement combination strength envelopes from single and multi-interface direct shear tests for the same geosynthetic/geosynthetic, geosynthetic clay liner (GCL)/geomembrane, and soil/geosynthetic interfaces. This comparison shows an agreement between the strength envelopes derived from single and multi-interface tests but there is a difference in the critical interface for some of the normal stresses and interfaces tested. The test results are also used to illustrate the effect of different types of geomembranes, soil type, and GCL hydration on the peak and large displacement strength envelopes.