Now showing 1 - 10 of 73
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    Cyclic Behaviour of Pond Ash-Based Controlled Low Strength Material
    (01-01-2020)
    Dev, K. Lini
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    Flowable fills, also called as Controlled Low Strength Materials (CLSM), are often used as alternative to compacted granular materials in specific situations like bedding layer to buried pipelines and backfill behind retaining walls. The fills are widely used in places where compaction cannot be done due to inaccessibility for moving compaction equipment and are often subjected to cyclic loading. While several studies are available in the literature on the static behaviour of flowable fills, the cyclic behaviour of flowable fills received less attention. This paper focuses on the cyclic behaviour of pond ash-based flowable fills. Comparative studies were carried out on compacted pond ash (CPA) specimens prepared at both standard and modified Proctor unit weight and optimum moisture content for similar testing conditions. The cyclic behaviour was studied by performing cyclic triaxial tests for different cyclic stress ratio (CSR) on both compacted pond ash and flowable fill. The results obtained based on cyclic triaxial tests showed that the flowable fills perform much better compared to the compacted pond ash specimens.
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    One-dimensional consolidation stress and Atterberg limits of reconstituted fine-grained soils
    (16-11-2020)
    Jyothsna, V.
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    The Atterberg limits–liquid limit (w L), plastic limit (w P) and shrinkage limit (w S) are of great importance for fine-grained soils. Though the procedure for their determination is empirical in nature, attempts were made in the literature to provide meaningful interpretation. In the present study, it is attempted to find out the consolidation pressure required to reach the liquid limit and plastic limit water contents when a slurry specimen is subjected to one-dimensional consolidation. Experiments were conducted on 10 soil samples of varying plasticity characteristics. The average effective consolidation pressure required to consolidate the specimen to the liquid limit and plastic limit void ratio was found to be 10 kPa and 600 kPa, respectively. Further analysis shows that the findings are in agreement with the data available in the literature. Therefore, there is scope for developing a test method to determine the Atterberg limits based on one dimensionally consolidating reconstituted soil specimens.
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    Estimation of Critical State Parameters from One-dimensional Consolidation and Triaxial Compression Tests
    (01-09-2013)
    Dev, K. Lini
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    Pillai, Rakesh J.
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    Determination of critical state parameters are essential, when critical state soil mechanics based soil models are used for the analysis. Isotropic consolidation test and triaxial tests with accurate measurements of volume change and pore pressure are essential for the direct measurement of critical state parameters. However, in the conventional geotechnical engineering practice, isotropic compression tests are usually not conducted but only one-dimensional consolidation test are performed. The usual parameters reported in most of the soil investigation reports are the shear strength parameters c′ and φ{symbol}′ and the consolidation parameters such as compression index (Cc) and the recompression index (Cr) apart from, the overburden pressure σ0′ and the corresponding void ratio e0. The critical state parameters are seldom reported in most of the soil investigation reports. This paper explains a procedure to estimate the critical state parameters, in the absence of isotropic compression test data, based on one-dimensional consolidation tests and triaxial compression tests, using the equations of Modified Cam clay state boundary surface. Comparison of the calculated values from the suggested method with the measured values, on three reconstituted soils and one undisturbed soil, lends support to the validity of the proposed procedure. © 2013 Indian Geotechnical Society.
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    Deformation behaviour of soil under vacuum consolidation
    (16-11-2010)
    Deepa, B. R.
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    Vacuum preloading technique is a viable ground improvement technique for the stabilization of soft grounds. The basic difference between surcharge preloading and vacuum preloading is that surcharge preloading imparts anisotropic stress conditions to the soil whereas the stress induced by vacuum pressure is more close to isotropic as it is applied to the pore phase. Therefore, the soil deform in the outward direction in the former case where as it is inward in the latter case. Though vacuum consolidation technique is extensively used in practice, the mechanism of soil deformation is not properly evaluated in the literature. This paper examines this aspect through an experimental programme on a reconstituted soil using a double wall triaxial cell. Apart from monitoring the vertical deformation, the lateral strain was also computed. It was found that the vertical settlement under vacuum consolidation is less than that obtained from one-dimensional consolidation under the same consolidation pressure. The vertical settlement under vacuum pressure is same as that under equivalent surcharge loading, if 1-D condition prevails. Copyright © 2009 by Geotechnical Society of Singapore (GeoSS).
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    A combined split-spoon sampler and spherical penetrometer: laboratory trials
    (01-01-2018)
    Mishra, S.
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    Full flow penetrometers (FFPs) such as T-bar and ball penetrometer provide reliable estimates of undrained shear strength (su) of soft-soil deposits. Several studies are reported in the literature on the field application of these penetrometers for offshore applications typically for the deep-water environment. However, the lack of sampling provision creates problem for identifying the accurate soil type from the load–penetration response. Information obtained from the field samples is vital in determining the stratigraphy and conducting several basic laboratory tests. This study proposes a new sampling-cum-penetration testing device, which uses a split-spoon sampler for sampling with a spherical cutting shoe. The cutting shoe was modified to increase the bearing area for enhanced accuracy in soft deposits. Strength assessment study was conducted in the laboratory using remoulded kaolin clay at various undrained shear strengths. To investigate the occurrence of plugging and the extent of influence zone during penetration, image-based deformation measurement technique was adopted. The modified ball penetrometer shows a strength factor of about 14·3 in remoulded kaolin clay.
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    Shear strength behavior of cement treated marine clay
    (01-10-2012)
    Bushra, I.
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    The in-situ deep cement mixing method is an established technique for improving the strength and reducing settlement of soft soil deposits. In practice, upon completion of the cement treatment, the improved ground will be left for curing over a specific period of time, before commencement of construction activities. In the case of deep mixing, curing takes place under the overburden pressures, at deeper depths. Studies on the influence of curing stress on the stress-strain and strength characteristics of cement stabilized clays are limited. The role of curing stress on the strength behavior of the cement treated soil is studied in this paper. Consolidated undrained triaxial compression tests performed on cement treated samples cured with and without stress are mainly focused. Marine clay from Ennore, near Chennai, India, excavated at a depth of 1.5 m was selected for the study. The range of cement contents selected were 10%, 15% and 20% with curing time of 28 days. The curing stresses adopted were 0, 50, 100 and 200 kPa. Additional tests were also conducted to study the effect of lower cement content of 5% and the effect of higher confining pressures.
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    Distress of an industrial building constructed on an expansive soil: A case study from India
    (12-04-2018)
    Ashok Kumar, T.
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    This paper presents a case study of a two-storey building in Oragadam, near Chennai (India), which has undergone distress due to the presence of expansive soil. Undulations in the floors, cracks in partition walls and non-uniform heave in the pavement are some of the failure patterns noticed in and around the structure. Undisturbed soil samples were collected from the site to identify the cause of distress. From the field inspection and laboratory testing it was found that the use of unsuitable fill material (expansive soil) followed by the ingress of excess water from the garden and improper planning of the location of the rainwater-harvesting system were the causes of the initiation of distress in the building.
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    Cyclic swell-shrink behavior of lime column stabilized expansive soil
    (01-12-2010)
    Bhuvaneshwari, S.
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    The cyclic swell shrink behaviour of expansive soils due to alterations in moisture content causes extensive distress to structures found on them. The volume change behaviour of the lime column stabilized expansive soil, under repeated wetting and drying is studied in the present investigation. The tests are carried out in modified oedometer cells at controlled temperature of 40 ± 5°C for faster drying. Diameter ratio of soil to lime column was varied and different techniques were adopted to improve the rate of diffusion. Microstructure observations were made through Scanning Electron Microscope studies. The equilibrium magnitude of swell-shrink is reached after about six to seven cycles. The lime column takes at least two cycles to get diffused into the surrounding soil to curtail the swelling. The subsequent shrinkage induced cracks enabled faster diffusion into the soil. © 2010 Taylor & Francis Group, London.
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    A rapid method of determination of swell potential and swell pressure of expansive soils using constant rate of strain apparatus
    (16-01-2020)
    Ashok Kumar, T.
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    Raheena, M.
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    Swell potential and pressure of expansive soils are conventionally determined using an oedometer apparatus. The specimens are commonly saturated by submerging in water under a seating pressure. Generally, the test takes a long time, as the saturation process is slow. This article presents an improved saturation method by back pressure application in a constant rate of strain (CRS) loading apparatus. Controlled strain loading (CSL) was adopted to bring back the swollen specimens to their initial thickness instead of conventional incremental loading. It is observed that the time taken to complete the test is 7 to 13 times faster compared to the conventional method. When compared to the conventional method, the swell potential and pressure values obtained with the back pressure saturation were found to be higher by about 19 % to 34 % and 6 % to 28 %, respectively. The reason for these higher values is attributed to the attainment of greater saturation using the back pressure saturation technique.
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    Constant Rate of Strain Consolidation Test Using Conventional Fixed Ring Consolidation Cell
    (01-04-2019)
    Moozhikkal, Raheena
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    Sridhar, G.
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    This paper describes a modified conventional fixed ring consolidation cell to perform constant rate of strain (CRS) consolidation test for determining consolidation properties of soils. The modified consolidation cell is similar to the conventional oedometer cell with an additional provision for measuring pore water pressure at the bottom of the soil specimen. Detailed description of the modifications required in the conventional consolidation cell is provided. The performance of the apparatus is validated by performing CRS consolidation tests on four types of reconstituted soil specimens and one undisturbed soil specimen. The test results obtained from the proposed CRS apparatus were compared with the results obtained from the incremental loading consolidation tests. The test results prove that the modified consolidation cell is very well suited for performing CRS tests to determine the consolidation properties of soils.