Shear behavior of an unsaturated soil-steel interface from direct shear tests

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Analysis of Soil-Compacting Effect Caused by Shield Tunneling Using Three-Dimensional Elastoplastic Solution of Cylindrical Cavity Expansion

This is the final version of the article. Available from Hindawi via the DOI in this record.Soil squeezing effect and formation disturbance caused by tunnel excavation can be simulated by cylindrical cavity expansion due to the comparability between tunneling and cavity expansion. Although most of the existing theoretical derivation is based on simple constitutive model of soil foundation, not only the relation between principal stress components was simplified in the solution process, but also the stress history, initial stress anisotropy, and stress-induced anisotropy of structural soil were neglected. The mechanical characteristics of soil are closely related to its stress history, so there is a gap between the above research and the actual engineering conditions. A three-dimensional elastoplastic solution of cylindrical cavity expansion is obtained based on the theory of critical state soil mechanics and engineering characteristics of shield tunneling. In order to fully consider the influence of initial anisotropy and induced anisotropy on the mechanical behavior of soils, the soil elastoplastic constitutive relation of cavity expansion is described in the course of K0-based modified Cam-clay (K0-MCC) model after soil yielding. An equation with equal number of variables is obtained under the elastic-plastic boundary condition based on the Lagrange multiplier method. By solving the extreme value of the original function, the analytical solution of radial, tangential, and vertical effective stresses distribution around the circular tunnel excavation is obtained. In addition, changes of elastic deformation area and plastic deformation area for soil during the shield excavation have been analyzed. Calculation results are compared with the numerical solutions which usually consider isotropic soil behavior as the basic assumption. In this paper, a constitutive model which is more consistent with the actual mechanical behavior of the soil and the construction process of the shield tunnel is considered. Therefore, the numerical solutions are more realistic and suitable for the shield excavation analysis and can provide theoretical guidance required for design of shield tunneling.This work is supported by the National Natural Science Foundation of China (no. 41172238)

CLASSIFICATION AND ASSESSMENT OF THE LAND USE – LAND COVER CHANGES IN JODHPUR CITY USING REMOTE SENSING TECHNOLOGIES

Land Use – Land Cover (LULC) classification mapping is an important tool for management of natural resources of an area. The remote sensing technology in recent times has been used in monitoring the changing patterns of land use-land cover. The aim of the study is to monitor the LULC changes in Jodhpur city over the period 1990–2018. Satellite imagery of Landsat 8 OLI (June, 2018) & Landsat TM (Oct, 1990) were used for classification analysis. Supervised classification-maximum likelihood algorithm is used in ENVI software to detect land use land cover changes. Five LULC categories were used, namely- urban area, mining area, vegetation, water bodies and other area (Rock outcrops and barren land). The LULC classified maps of two different periods i.e. 2018 and 1990 were generated on 1 : 50,000 scale. The accuracy assessment method was used to measure the accuracy of classified maps. This study shall be of good assistance to the town planners of Jodhpur city for the purpose of the sustainable development as per the master plan 2031

A Modified Suction-Controlled Direct Shear Device for Testing Unsaturated Soil and Steel Plate Interface

The interfaces between saturated/unsaturated and structure are common to many offshore and on-shore civil engineering structures, but their behavior is not well understood. The shearing behavior of the interface plays a significant role in the stability and serviceability of the associated structures. With this in view, to study the influence of matric suction on interface (a stainless steel plate), a suction-controlled direct shear apparatus was modified. The main modifications included the fabrication of the shear box base/test cell for interface testing, along with some other important features and modifications that are described in this paper. By utilizing the modified direct shear apparatus, several suction-controlled direct shear tests were conducted on both the soil and the soil-steel plate interface. The main aim of this study was to develop laboratory testing equipment that can be used to determine shear strength of unsaturated soil-steel interfaces, at different shearing planes. The typical test results obtained from the study are presented and discussed in this paper, and it has been observed that the modified apparatus is suitable for testing the unsaturated soil-steel plate interfaces

Direct Shear Testing Study of the Interface Behavior between Steel Plate and Compacted Completely Decomposed Granite under Different Vertical Stresses and Suctions

In this paper, the shearing behavior of soil-steel interfaces sheared at different planes is examined using a modified suction-controlled direct shear apparatus (MDSA). Direct shear tests on soil-steel interfaces sheared at three shear planes at three different suction values were conducted. Test results show that matric suction has a significant influence on interface shear behavior and shear strength and that the critical (or minimum) interface shear strength depends on the applied matric suction. Net normal stress affects both peak and postpeak shear stresses of the interfaces and those of the pure soil. The suction envelope for the interfaces is nonlinear. The interface shear strength values from experimental results are compared with the values predicted from an existing analytical model that considers the influence of soil dilation. The results indicate that the analytical model is suitable for predicting the unsaturated interface shear strength of rough soil-steel interfaces. (C) 2017 American Society of Civil Engineers

Accumulated permanent axial strain of a subgrade fill under cyclic high-speed railway loading

Title on author’s file: "Test Study and Analysis of Accumulated Permanent Axial Strain of a Subgrade Fill under Cyclic High-Speed Railway Loading"202310 bcchAccepted ManuscriptOthersKey Project Grant (Grant No. U1234204) from National Natural Science Foundation of China; Hong Kong Polytechnic UniversityPublishe

Prévalence du syndrome des antiphospholipides au cours de la thrombose veineuse profonde des membres inférieurs et de l'occlusion de la veine centrale de la rétine

POITIERS-BU Médecine pharmacie (861942103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Interface behaviour from suction controlled direct shear test on completely decomposed granitic soil and steel surfaces

A soil-structure interface is defined as the contact surface between a soil and a structure through which stresses are transferred from the soil to the structure or vice versa. The ultimate shear strength at the interface is one of the key parameters required for the design and safety assessment of a structure in the soil, such as pile foundations, retaining walls, buried pipelines, and soil nails. In this paper, the shearing behavior of completely decomposed granite soil and steel interfaces is examined using a modified suction-controlled direct shear apparatus. A series of direct shear tests was performed on two different types of soil-steel interfaces under different stress state variables. The experimental results were used to investigate the influence of counterface roughness on the failure envelopes of soil-steel interfaces. Test results show that matric suction has a significant influence on the shear behavior and shear strength of the interfaces. It has been observed that the critical interface shear strength for a specific counterface roughness and net normal stress (NNS) depends on the applied matric suction. Also, both the peak and the postpeak shear stresses are greatly influenced by variation in NNS. Furthermore, the experimental shear strength data are compared with an analytical model that considers the influence of suction and dilation on an apparent interface friction angle. It is noted that, for the applied NNS and matric suction, the analytical model works well for both rough interfaces