Effect of wetting on the collapsibility and shear strength of tropical residual soils (original) (raw)
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Effect of Wetting on Collapsibility and Shear Strength of Tropical Residual Soils
Electronic Journal of Geotechnical …, 2008
Residual soils with extensive weathering of parent materials can yield collapsible soil deposits. In Malaysia, residual granite and sedimentary rock soils occur extensively, i.e. cover more than 80% of the country's land area. These types of soil have a high possibility to collapse when wetted. This paper described a study that had been carried out to examine the effect of wetting on the collapsibility and shear strength of the tropical residual soils. Odometer tests (single and double) and double shear box tests were carried out on selected soil samples. In addition Scanning Electron Microscopic (SEM) test and X-Ray Diffraction Analysis were also carried out. From the result obtained, both types of soils were found to collapse upon wetting (inundation). The finer granitic residual soil (MH) apparently showed a slightly higher collapse potential compared with the relatively coarser sedimentary residual soil (SM). The SEM analysis indicated that the soil structure became more compacted and voids between the structures became smaller upon collapse. The shear strength tests showed that the shear strength of both soil reduced significantly upon collapse, in particular the soil apparent cohesion, with the granitic residual soil showing more strength reduction compared with the sedimentary residual soil.
Characterization the geotechnical properties of a Malaysian granitic residual soil grade V
IOP Conference Series: Earth and Environmental Science, 2019
Residual soils are produced from weathering of rocks and commonly found in tropical humid areas. The geotechnical properties of residual soils are a function of the parent rock, the degree of weathering, and climate which vary from region to region. A thorough quantification of the geotechnical characteristics of residual soils is required for a safe and economic structure design. This study attempts to summarize a series of important geotechnical properties of a Malaysian granitic residual soil grade V which determine the suitability and ability of the soil for construction including particles size distribution, specific gravity, plastic index, soil-water characteristic curve, and shear strength. The findings were compared with geotechnical properties of other residual soils which were reported previously. The results showed weathering grade and the percentage of fine particles are the two important factors in controlling the geotechnical properties of residual soils.
Collapsibility and Volume Change Behavior of Unsaturated Residual Soil
American Journal of Environmental Sciences, 2006
Residual soils occur in most countries of the world but the greater areas and depths are normally found in tropical humid areas. In these places, the soil forming processes are still very active and the weathering development is much faster than the erosive factor. Most residual soil exhibit high suctions for most of the year. The absence of positive pore water pressure except immediately after rain, makes conventional soil mechanics for saturated soil not so relevant. Ignorance or lack of understanding of the geotechnical behavior of soil in the partially or unsaturated state has caused a lot of damages to infrastructures, buildings and other structures. For instance, the collapsibility and volume change of partially saturated soils in connection with the drying or wetting causes a lot of damage in foundation, roads and other structures. It is also observed that many shallow slope failures involve a slumping (collapse) type of failure. As such, the development of extended soil mechanics, which embraces the soil in the unsaturated state or subjected to soil suction, is essential. This study examines the collapsibility and volume change behavior specifically of an unsaturated residual soil under various levels of applied matric suction (u a-u w) and net mean stress (σ-u a) in a predetermined stress path. The volume change of the soil is found to be sensitive to both the applied matric suction and net mean stress. The soil is found to exhibit a collapsibility behavior upon a reduction in applied matric suction at constant net mean stress.
The residual shear strength of tropical soils
Canadian Geotechnical Journal, 2006
The paper discusses the residual shear strength of tropical soils. Ring shear tests have been performed with tropical soils from southern Brazil using the Bromhead apparatus. The data from the study are compared with data obtained in a comprehensive literature review of the subject. The residual friction angle of tropical residual soils from sedimentary formations decreases with increasing plasticity index following a general trend presented in the literature. Most of the residual soils described herein have also shown this trend. However, some of these residual soils, particularly basalt saprolitic soils, have shown quite low residual friction angles despite having low plasticity index and clay fraction values. It has been confirmed that the residual shear strength of tropical soils depends chiefly on mineralogy, particle size distribution, effective stress, parent rock, weathering degree, pedogenetic evolution and - when partly weathered minerals are present - degradation upon she...
Variability of residual soil properties
Engineering Geology, 2012
Rainfall-induced slope failures are commonly observed in residual soil. Due to weathering, the residual soil properties vary with depths, especially in tropical countries, such as: Singapore. Therefore, it is important to characterize the properties of residual soil with depth. Index properties, soil-water characteristic curve and saturated and unsaturated shear strength tests were carried out on residual soils from sedimentary Jurong Formation, Bukit Timah Granite and Old Alluvium in Singapore. The variations of residual soil properties in Singapore were determined from the laboratory test results and evaluated as a function of soil inherent variability. Typical, upper and lower bounds of soil properties for the residual soils in Singapore were described using confidence interval approach and coefficient of variation (COV) in this paper. The variations in residual soil properties can be incorporated in design based on risk or reliability approach. The COV of index and engineering properties of residual soils in Singapore indicate that residual soils from Bukit Timah Granite and Old Alluvium are coarser than residual soil from sedimentary Jurong Formation. The particle size distribution of residual soil from Old Alluvium is more uniform than that from Bukit Timah Granite. On the other hand, the particle size distribution of residual soil from Bukit Timah Granite is more uniform than that from sedimentary Jurong Formation. The shear strengths of residual soils from Bukit Timah Granite and Old Alluvium are higher than that from sedimentary Jurong Formation.
Influence of Fine Fraction on Shear Parameters and Consolidation Behavior of Tropical Residual Soil
Indian Journal of Science and Technology, 2016
Objectives: Tropical residual soils are widely available in the southern part of India and the construction in this type of soils more challenge issue to the geotechnical engineers to design the structure in the settlement criteria. Analysis: Tropical residual soils are in general are regarded as multi component, polyphase, and particulate system with compositional and/ or structural discontinuities. Both index and engineering properties of natural soils primarily depend on mineralogy and percentage of fine fraction. Findings: In this paper, eight soil samples are considered for to obtain the influence of the fine fraction on shear parameters and consolidation behavior of tropical residual soils in Tirupati region. Shear strength tests and one-dimensional compression tests have been conducted apart from the classification and identification tests. Application/ Improvement: Based on the experimental test results and analysis, it has been found that the percentage fine fraction has a greater significant influence on engineering properties like cohesion, angle of internal friction and compression index of tropical residual soils.
Laterites are used extensively as construction materials in Nigeria. Particle size distribution of the laterites from the sedimentary basin of Southern Nigeria show that laterites are composed of sands and clays. The dependence of the shear strength and compressibility on their clay content is investigated using field samples of sand and clay mixtures. The results show that the soils cohesion, plasticity index and compressibility index are directly proportional to the clay content, while the friction angle and initial void ratio are inversely proportional to the clay content at the same moisture content. Copyright © IJEATR, all rights reserved. Keywords: Clay content; sand and clay mixtures; soils cohesion; plasticity index; compressibility index; friction angle; initial void ratio
The engineering behaviour of the tropical clay soils of Dhaka, Bangladesh
Introduction 119 6.2 Consolidation characteristics 6.2.1 Volume change vs. time curves for triaxial consolidation 121 6.3 Consolidation parameters 6.3.1 Coefficient of consolidation 124 6.3 .. 2 Coefficient of volume compressibility 126 6.3.3 Void ratio vs. p' curves 128 6.3.4 Compression index 6.3.5 Coefficient of permeability 129 6.4 Summary 131 CHAPTER 7 UNDRAINED TRIAXIAL TESTS 147 157 7.2.3.7 Small strain behaviour 162 7.2.3.7.1 Tangential stiffness vs. mean effective stress (up to 2%) 163 Ill 7.2.3.7.2 Deviator stress vs. mean effective stress for natural soils of borehole one and two (up to 2% strain) 7.3 Consolidated undrained triaxial tests on destructured soils of borehole one and two 165 7.3.1 Stress strain curves of destructured soils of borehole one and two 167 7.3.2 Excess p.w.p. vs. strain curves for destructured soils of borehole one and two 169 7.3.3 q/p' ratio vs. strain for destructured soils of borehole one and two 171 7.3.4 Stress paths for destructured soils of borehole one and two 172 7.4 Failure surface for destructured soils of borehole one and two 173 7.5 Small strain behaviour 7.5.1 Tangential stiffness vs. mean effective stress (up to 2%) 174 7.5.2 Deviator stress vs. mean effective stress for destructured soils of borehole one and two (up to 2% strain) 7.6 Comparisons between the behaviour of the natural and destructured soils of borehole one and two 7.6.1 Comparions between the stress strain behaviour of natural and destructured soils of borehole one and two 7.6.2 Comparions between the of natural and destructured failure surfaces of borehole one and two 7.6.3 Comparisons between tangential stiffness vs. mean effective stress (up to 2%) for natural and destructured soils 179 7.6.4 Comparisons between strain contours for natural and destructured soils of borehole one and two 7.7 Critical state behaviour 181 7.7.1 Critical state behaviour for natural soils of borehole one & two 181 7.7.2 Critical state behaviour for destructured soils of borehole one and two 183 7.7.3 Comparison between critical state behaviour of natural and destructured soils IV 7.8 Comparisons between the behaviour of the natural soils of two boreholes 187 7.9 Comparisons between the stress strain behaviour of the destructured soils of two boreholes 7.10 Framework for the tropical clay soils of Dhaka, Bangladesh 7.10.1 Undrained characteristics to identify zones of behaviour 191
Characterization and Geotechnical Properties of Penang Residual Soils with Emphasis on Landslides
American Journal of Environmental Sciences, 2006
The predominantly hilly terrain of Penang Island combined with average maximum daily temperatures ranging between 27-35 o C and peak rainfall as high as 647 cm makes the overall area potentially susceptible to landslips. Over the recent past construction industry has shown a rapid growth mainly due to increase in the inflow of international tourists and other economic reasons. Eventually, the magnitude of disaster associated with landslides has also increased and that is one of the major concerns of engineering geologists and geotechnical engineers. With this background this paper attempts to characterize the largely granitic residual soils of Penang Island by discussing the nature, structural features, engineering behavior and field properties of soil samples extracted from 8 sites. These sites are distinctly chosen from a database of 31 sites for they are located over different prime geological formations. The mean values of various design properties at different depths are calculated and plotted to identify the property trend with depth and important behavioral features relevant to landslides are discussed. Similarly, compression index values are plotted against initial void ratio and liquid limit separately and resulting correlations are compared with the established ones. Correlations given by Azzous are found to hold good. Lastly, in the light of the lessons learnt from the past landslides and the current characterization results some improvements regarding slope instability problem are discussed.
Geotechnical Behaviour of Some Unsaturated Tropical Clay Soils of Dhaka, Bangladesh
Experimental testing has been carried out on samples collected from a borehole in the Curzon Hall area of Dhaka to investigate the geotechnical behaviour of some unsaturated tropical clay soils from Dhaka, Bangladesh. The soil was tested in its natural (undisturbed) state and also after destructuration in order to assess the influence of the natural iron oxide cementing on the strength and stiffness. Natural specimens consolidated at effective stresses below 500 kPa show a change in stiffness that can be interpreted as bond yield. The tests also show a difference in failure envelope between the natural and destructured specimens, confirming the influence of the iron oxide bonding on both stiffness and strength. Values of the Critical State stress ratio M were found to be 0.95-0.96.