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CONTENTS
Volume 23, Number 4, November25 2020
 

Abstract
In this study, shear strength behavior of fine-grained soils was investigated under unsaturated conditions. The samples in the unsaturated state were subjected to a net normal stress (σ-u_a) of 40 kPa and different matric suctions (u_a-u_w) of 50, 100 and 150 kPa. The matric suction values applied in the triaxial tests were selected according to the bubbling pressures determined from the SWC curves. The study was carried out on prepared re-constituted cylindrical samples by uniaxial consolidation of soil slurries. First, consolidated drained (CD) triaxial compression tests were performed on the saturated samples and the cohesion and angle of internal friction were determined. After that, drained triaxial compression tests under matric suctions were performed on the unsaturated samples. In order to obtain unsaturated test results, cohesion and internal friction angle values of saturated samples were used. The nonlinear surface representing the shear strength surface was approximated consisting of two planes (double planar surface). The reason for the nonlinear behavior of some soils is that the amount of sand content contained in it is relatively high and the bubbling pressure/permanent water content value is relatively low.

Key Words
unsaturated soil; shear strength; soil behavior; suction; failure

Address
Kurban Onturk: Institute of Natural Sciences, Sakarya University, Sakarya 54187, Turkey

Ertan Bol and Aşkin Ozocak: Department of Civil Engineering, Sakarya University, Sakarya 54187, Turkey

Tuncer B. Edil: Department of Civil & Environmental Engineering, University of Wisconsin-Madison, Madison, WI 53706, U.S.A.

Abstract
Slope displacement and factor of safety (FOS) of a slope are two aspects that reflect the stability of a slope. However, the traditional limit equilibrium (LE) methods only give the result of the slope FOS and cannot be used to solve for the slope displacement. Therefore, developing a LE method to obtain the results of the slope FOS and slope displacement has significance for engineering applications. Based on a force-displacement coupled mode, this work expands the LE Morgenstern-Price (M-P) method. Except for the mechanical equilibrium conditions of a sliding body adopted in the traditional M-P method, the present method introduces a nonlinear model of the shear stress and shear displacement. Moreover, the energy equation satisfied by a sliding body under a small slope displacement is also applied. Therefore, the double solutions of the slope FOS and horizontal slope displacement are established. Furthermore, the flow chart for the expanded LE M-P method is given. By comparisons and analyses of slope examples, the present method has close results with previous research and numerical simulation methods, thus verifying the feasibility of the present method. Thereafter, from the parametric analysis, the following conclusions are obtained: (1) the shear displacement parameters of the soil affect the horizontal slope displacement but have little effect on the slope FOS; and (2) the curves of the horizontal slope displacement vs. the minimum slope FOS could be fitted by a hyperbolic model, which would be beneficial to obtain the horizontal slope displacement for the slope in the critical state.

Key Words
slope stability; limit equilibrium; Morgenstern-Price method; force-displacement coupled mode; factor of safety; horizontal slope displacement

Address
Dong-ping Deng, Kuan Lu, Sha-sha Wen and Liang Li: School of Civil Engineering, Central South University, Changsha 410075, China

Abstract
The role of precise prediction of subsurface fluids and discrimination among them cannot be ignored in reservoir characterization and petroleum prospecting. A suitable rock physics model should be build for the extraction of valuable information form seismic data. The main intent of current work is to present a rock physics model to analyze the characteristics of seismic wave propagating through a cracked porous rock saturated by a three phase fluid. Furthermore, the influence on wave characteristics due to variation in saturation of water, oil and gas were also analyzed for oil and water as wet cases. With this approach the objective to explore wave attenuation and dispersion due to wave induce fluid flow (WIFF) at seismic and sub-seismic frequencies can be precisely achieved. We accomplished our proposed approach by using BISQ equations and by applying appropriate boundary conditions to incorporate heterogeneity due to saturation of three immiscible fluids forming a layered system. To authenticate the proposed methodology, we compared our results with White's mesoscopic theory and with the results obtained by using Biot's poroelastic relations. The outcomes reveals that, at low frequencies seismic wave characteristics are in good agreement with White's mesoscopic theory, however a slight increase in attenuation at seismic frequencies is because of the squirt flow. Moreover, our work crop up as a practical tool for the development of rock physical theories with the intention to identify and estimate properties of different fluids from seismic data.

Key Words
exploration geophysics; mathematical geophysics; seismic methods; seismology; waves and wave analysis; geomechanics measurements and monitoring

Address
Qazi Adnan Ahmad: 1.) Department of Geology and Geophysics, Bacha Khan University Charsadda, KPK, Pakistan
2.) China University of Petroleum (East China), School of Geoscience Qingdao, Shandong, 266555, China

Guochen Wu, Zhaoyun Zong, Jianlu Wu and Zeyuan Du: China University of Petroleum (East China), School of Geoscience Qingdao, Shandong, 266555, China

Muhammad Irfan Ehsan: Institute of Geology University of the Punjab, Lahore 54590, Pakistan

Abstract
This study investigates the feasibility of using the results of the UPV (ultrasonic pulse velocity) test to assess the UCS (unconfined compressive strength) of unsaturated soil. A series of laboratory tests was conducted on samples of unsaturated lateritic soils of northern Taiwan. Specifically, the unconfined compressive test was combined with the pressure plate test to obtain the unconfined compressive strength and its matric suction (s) of the samples. Soil samples were first compacted at the designated water content and subsequently subjected to the wetting process for saturation and the following drying process to its target suction using the apparatus developed by the authors. The correlations among the UCS, s and UPV were studied. The test results show that both the UCS and UPV significantly increased with the matric suction regardless of the initial compaction condition, but neither the UCS nor UPV obviously varied when the matric suction was less than the air-entry value. In addition, the UCS approximately linearly increased with increasing UPV. According to the investigation of the test results, simplified methods to estimate the UCS using the UPV or matric suction were established. Furthermore, an empirical formula of the matric suction calculated from the UPV was proposed. From the comparison between the predicted values and the test results, the MAPE values of UCS were 4.52-9.98% and were less than 10%, and the MAPE value of matric suction was 17.3% and in the range of 10-20%. Thus, the established formulas have good forecasting accuracy and may be applied to the stability analysis of the unsaturated soil slope. However, further study is warranted for validation.

Key Words
unsaturated soil; matric suction; unconfined compressive strength; ultrasonic pulse velocity; prediction model

Address
Chien-Chih Wang: Department of Civil Engineering and Geomatics, Cheng Shiu University, Kaohsiung 83347, Taiwan

Horn-Da Lin, An-Jui Li and Kai-En Ting: Department of Civil and Construction Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan

Abstract
This paper numerically investigates the effects of a dip-slip fault (a normal or a reverse fault) movement on a segmental tunnel which transversely crosses either of this kind of faults. After calibration of the numerical model with results from literature of centrifuge physical tests, a parametric study is conducted to evaluate the effects of various parameters such as the granular soil properties, the fault dip angle, the segments thickness, and their connections stiffnesses on the tunnel performance. The results are presented and discussed in terms of the ground surface and tunnel displacements along the longitudinal axis for each case of faulting. The gradient of displacements and deformations of the tunnel cross section are also analyzed. It is shown that when the fault dip angle becomes greater, the tunnel and ground surface displacements are smaller, in the case of reverse faulting. For this type of fault offset, increasing the tunnel buried depth causes tunnel displacements as well as ground surface settlements to enhance which should be considered in the design.

Key Words
segmental tunnel; normal fault; reverse fault; numerical simulation; soil

Address
Milad Zaheri and Masoud Ranjbarnia: Department of geotechnical Engineering, Faculty of civil engineering, University of Tabriz, 29 Bahman Blvd, Tabriz, Iran

Daniel Dias: 1.) School of Automotive and Transportation Engineering, Hefei University of Technology, Hefei, China
2.) Grenoble Alpes University, Laboratory 3SR, 38401 Grenoble Cedex 9, France
3.) Antea Group, Anthony, France

Abstract
One of the leading causes for the damage of various underground structures during an earthquake is soil liquefaction, and among this liquefaction-induced uplift of these structures is a major concern. In this study, finite-difference modelling is carried out to study the liquefaction-induced uplift of an underground structure of 5 m diameter (D) with and without the replacement of the in-situ fine sand around the structure with the coarse sand. Soil replacements are carried out by three methods: replacement of soil above the structure, around the structure, and below the structure. The soil behaviour is represented using the elastic-perfectly plastic Mohr-Coulomb model, where the pore pressures were computed using Finn-Byrne formulation. The predicted pore pressure and uplift of the structure due to sinusoidal input motion were validated with the centrifuge tests reported in the literature. Based on numerical studies, an empirical equation is developed for the determination of liquefaction-induced maximum uplift of the underground structure without replacement of the in-situ sand. It is found that the replacement of soil around the structure with 2D width and spacing of D can reduce the maximum uplift by 50%.

Key Words
finite difference modelling; underground structure; liquefaction-induced uplift; pore pressure response; mitigation; replacement of soil

Address
Priya Beena Sudevan, A. Boominathan and Subhadeep Banerjee: Department of Civil Engineering, Indian Institute of Technology, Madras, Chennai 600036, India

Abstract
The difficulties, challenges and limitations faced in standard pressuremeter testing in the measurement of low soil deformations led a number of researchers to think about the possible modification of the equipment, and especially the replacement of the volumeter by a Hall Effect sensor. This article is a major contribution in this direction. It makes an attempt to detail the design, manufacture and operation of the new equipment. The calibration of the various components was carried out according to the rules presently in force. This proposal was applied, on an exploratory basis, to the data of a real site located in France. The authors present the preliminary results of some cyclic pressuremeter tests, previously carried out in the laboratory, on a sandy material, and they then provide a basic interpretation of these results. The findings indicated that the proposed apparatus is capable of providing high-quality information about constraints and deformations. Although these tests were performed within the laboratory, it was possible to analyze the power, quality, performance and insufficiencies of the proposed equipment.

Key Words
soils; in-situ equipment; pressuremeter; testing of materials; measuring feeler; cyclic stress-strain

Address
Soufyane Aissaoui and Abdeldjalil Zadjaoui: Department of Civil Engineering, Tlemcen University, 22 rue Abi Ayed Abdelkrim, Fg Pasteur BP 119. 13000, Algeria

Philippe Reiffsteck: IFSTTAR-Paris, 14-20 Boulevard Newton Cite Descartes, Champs sur Marne F-77447, Marne la Vallee Cedex 2, France

Abstract
We design the Green-Naghdi model type III (GN-III) with widespread thermoelasticity for a thermoelectric half space using a memory-dependent derivative rule (MDD). Laplace transformations and state-space techniques are used in order to find the general solution for any set of limit conditions. A basic question of heat shock charging half space and a traction-free surface was added to the formulation in the present situation of a traveling heat source with consistent heating speed and ramp-type heating. The Laplace reverse transformations are numerically recorded. There are called the impacts of several calculations of the figure of the value, heat source spead, MDD parameters, magnetic number and the parameters of the ramping period.

Key Words
thermoelectric materials; Green-Naghdi of type III; memory-dependent derivative; ramp-type heating; moving heat source; state-space approach; Laplace transforms; numerical result

Address
Magdy A. Ezzat: 1.) Department of Mathematics, College of Science and Arts, Al Qassim University, Al Bukairyah, Saudi Arabia
2.) Department of Mathematics, Faculty of Education, Alexandria University, Alexandria, Egypt



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