Techno Press
Tp_Editing System.E (TES.E)
Login Search
You logged in as

gae
 
CONTENTS
Volume 29, Number 1, April10 2022
 


Abstract
A semi-analytical solution to responses of overconsolidated (OC) unsaturated soils surrounding an expanding spherical cavity under constant suction condition is presented. To capture the elastoplastic hydro-mechanical property of OC unsaturated soils, the unified hardening (UH) model for OC unsaturated soil is adopted in corporation with a soil-water characteristic curve (SWCC) and two suction yield surfaces. Taking the specific volume, radial stress, tangential stress and degree of saturation as the four basic unknowns, the problem investigated is formulated by solving a set of first-order ordinary differential equations with the help of an auxiliary variable and an iterative algorithm. The present solution is validated by comparing with available solution based on the modified Cam Clay (MCC) model. Parametric studies reveal that the hydraulic and mechanical responses of spherical cavity expanding in unsaturated soils are not only coupled, but also affected by suction and overconsolidation ratio (OCR) significantly. More importantly, whether hydraulic yield will occur or not depends only on the initial relationship between suction yield stress and suction. The presented solution can be used for calibration of some in-situ tests in OC unsaturated soil.

Key Words
cavity expansion; hydro-mechanical responses; overconsolidated unsaturated soil; suction

Address
Hui Wang, Changyi Yangand Jingpei Li: Department of Civil Engineering, Tongji University, Shanghai 200092, China

Abstract
Peat soil has the characteristics of high moisture content, large void ratio and low shear strength. In this study, unconfined compressive strength and SEM tests are conducted to investigate the effects of ultrahigh moisture content, cement content, organic content and pH value on the strength of solidified peat. As an increase in the cement content and curing period, the failure mode of solidified peat soil changes from ductile failure to brittle failure. The influence of moisture content on the strength of solidified peat is greater than the cement content. As cement content increases from 10% to 30%, strength of solidified peat at a curing age of 28 days increases by 161%~485%. By increasing water content by 100%, decreases of solidified peat at a curing age of 28 days is 42%~79%. Compared with the strength of solidified peat with a pH value of 5.5, the strength of peat with a pH value of 3.5 reduces by 10% ~ 46%, while the strength of peat with a pH value of 7.0 increases by 8% ~ 38%. It is recommended to use filler materials for stabilizing peat soil with moisture content greater than 200%. Because of small size of clay particles, clay added in the cement solidified peat can improve much higher strength that that of sand.

Key Words
cement content; moisture content; peat; pH value; unconfined compressive strength

Address
Rong Wang: China Harbour Engineering Company Ltd., Beijing, 100027, China;
School of Civil Engineering, Tianjin University, 300350, China

Abstract
In this study, 3D coupled-consolidation numerical parametric study was conducted to predict the deformation mechanism of a 20 storey building sitting on (4x4) piled raft (with length of piles, Lp=30 m) to adjacent 6 m diameter (D) tunnelling in stiff clay. The influences of different tunnel locations relative to piles (i.e., zt/Lp) were investigated in this parametric study. In first case, the tunnel was excavated near the pile shafts with depth of tunnel axis (zt) of 9 m (i.e., zt/Lp). In second and third cases, tunnels were driven at zt of 30 m and 42 m (i.e., zt/Lp = 1.0 and 1.4), respectively. An advanced hypoplastic clay model (which is capable of taking small-strain stiffness in account) was adopted to capture soil behaviour. The computed results revealed that tunnelling activity adjacent to a building resting on piled raft caused significant settlement, differential settlement, lateral deflection, angular distortion in the building. In addition, substantial bending moment, shear forces and changes in axial load distribution along pile length were induced. The findings from the parametric study revealed that the building and pile responses significantly influenced by tunnel location relative to pile.

Key Words
3D parametric study; 20 storey building: piled raft; different tunnel depths relative to pile length; tunnelling

Address
Mukhtiar Ali Soomro: School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou, Jiangsu, P. R. China
Naeem Mangi, Aftab Hameed Memon and Dildar Ali Mangnejo: Department of Civil Engineering, Quaid-e-Awam University of Engineering, Science & Technology, Sindh, Pakistan

Abstract
Tunneling in rocks having the time-dependent behavior, causes some difficulties like tunnel convergence and, as a result, pressure on concrete lining; and so instability on this structure. In this paper the time-dependent behaviour of squeezing phenomenon in a large cross section tunnel was investigated as a case study: Alborz tunnel. Then, time-dependent behaviour of Alborz tunnel was evaluated using FLAC2D based on the finite difference numerical method. A Burger-creep viscoelastic model was used in numerical analysis. Using numerical analysis, the long-time effect of squeezing on lining stability was simulated.This study is done for primary lining (for 2 years) and permanent lining (for 100 years), under squeezing situations. The response of lining is discussed base on Thrust Force-Bending Moment and Thrust Force-Shear Force diagrams analysing. The results determined the importance of consideration of time-dependent behaviour of tunnel that structural forces in concrete lining will grow in consider with time pass and after 70 years can cause instability in creepy rock masses section of tunnel. To show the importance of time-dependent behavior consideration of rocks, elastic and Mohr-Coulomb models are evaluated at the end.

Key Words
creep; burger-creep visco-plastic model (CVISC); numerical; time-dependent; tunnel

Address
Majid Mirzaeiabdolyousefi, Majid Nikkhahand Shokrollah Zare: Department of Mining, Petroleum & Geophysics Engineering, Shahrood University of Technology, Iran

Abstract
Simplified analytical solutions are developed for the dynamic analyses of an axially loaded pile foundation embedded in a transverse-isotropic, fluid-filled, poro-visco-elastic soil with rigid substratum. The pile is modeled as a viscoelastic Rayleigh-Love rod, while the surrounding soil is regarded as a transversely isotropic, liquid-saturated, viscoelastic, porous medium of which the mechanical behavior is represented by the Boer's poroelastic media model and the fractional derivative model. Upon the separation of variables, the frequency-domain responses for the impedance function of the pile top, and the vertical displacement and the axial force along the pile shaft are gained. Then by virtue of the convolution theorem and the inverse Fourier transform, the time-domain velocity response of the pile head is derived. The presented solutions are validated, compared to the existing solution, the finite element model (FEM) results, and the field test data. Parametric analyses are made to show the effect of the soil anisotropy and the excitation frequency on the pile-soil dynamic responses.

Key Words
Boer's poroelastic model; pile; transversely isotropic; poro-visco-elastic; separation of variables

Address
Shiping Zhang and Junhui Zhang: Key Laboratory of Road Structure and Material of Ministry of Transport (Changsha), China;
School of Traffic and Transportation Engineering, Changsha University of Science & Technology, Changsha 410114, Hunan, China
Ling Zeng: School of Civil Engineering, Changsha University of Science & Technology, Changsha 410114, Hunan, China
Cheng Yu: Dalian Bohai detection Co., Ltd, Dalian 116031, Liaoning, China
Yun Zheng: Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China

Abstract
Determination of strength properties of intact rock using artificial cores has been considered in recent years. In this study, some relationships for estimating the static properties of dolomudstone cores of the Asmari reservoir were presented using artificial cores prepared from cuttings of two wells, southwest of Iran. For this purpose, first natural cuttings (NC) and 33 cores including dolomite limestone (dolomudstone), anhydrite and anhydrite dolomite were prepared between depths of 1714 and 2208 meters. Petrographic, physical, mechanical and dynamic tests were performed on cores, NC and artificial cuttings (AC) which was prepared from the residuals of dolomudstone cores. For preparing the artificial cores, the average porosity of the dolomudstone cores was considered and determined using four methods. Artificial and natural cuttings were classified as dolomite limestone and dolomite limestone to calcareous dolomite, respectively. Using ordinary Portland cement (OPC), water, AC and NC artificial cores were prepared. Results of evaluating the proposed relationships using statistical criteria showed that the static properties of the artificial cores can be used to predict the static properties of the dolomudstone cores.

Key Words
artificial and natural cores; natural and artificial drill cuttings; petrography; static parameters

Address
Ahmad Rastegarnia, Mohammad Ghafoori, Naser Hafezi Moghaddas,Gholam Reza Lashkaripour: Department of Geology, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
Hassan Shojaei: National Iranian Oil Company, South Oil Company, Ahvaz, Iran

Abstract
Soybean-urease induced carbonate precipitation (EICP), as an alternative to microbially induced carbonate precipitation (MICP), was employed for soil improvement. Meanwhile, soluble calcium produced from industrial waste carbide slag powder (CSP) via the acid dissolution method was used for the EICP process. The ratio of CSP to the acetic acid solution was optimized to obtain a desirable calcium concentration with an appropriate pH. The calcium solution was then used for the sand columns test, and the engineering properties of the EICP-treated sand, including unconfined compressive strength, permeability, and calcium carbonate content, were evaluated. Results showed that the properties of the biocemented sand using the CSP derived calcium solution were comparable to those using the reagent grade CaCl2. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed that spherical vaterite crystals were mainly formed when the CSP-derived calcium solution was used. In contrast, spherical calcite crystals were primarily formed as the reagent grade CaCl2 was used. This study highlighted that it was effective and sustainable to use soluble calcium produced from CSP for the EICP process.

Key Words
biocementation; carbide slag powder (CSP); soil improvement; soybean crude urease extract; soybeanurease induced carbonate precipitation (EICP)

Address
Yongshuai Qi, Yufeng Gao, Hao Meng, Jia He and Yang Liu: Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University,
Nanjing 210098, China

Abstract
The cohesive non-swelling soil (CNS) cushion technology has been widely applied in the subgrade and slope improvement at expansive soil regions. However, the mechanism of the inhibition effect of the CNS layer on expansive soil (ES) has not been fully understood. We performed four outdoor model tests to further understand the inhibition effect, including different kinds of upper layer and thickness, under the unidirectional seepage condition. The swelling deformation, soil pressure, and electrical resistivity were constantly monitored during the saturation process. It is found that when a CNS layer covered the ES layer, the swelling deformation and electrical resistivity of the ES layer decreased significantly, especially the upper part. The inhibition effect of the CNS layer increases with the increase of CNS thickness. The distribution of vertical and lateral soil pressure also changed with the covering of a CNS layer. The electrical resistivity can be an effective index to describe the swelling deformation of ES layer and analyze the inhibition effect of the CNS layer. Overall, the CNS deadweight and the ion migration are the major factors that inhibit the swelling deformation of expansive soil.

Key Words
cohesive non-expansive soil; electrical resistivity; expansive soil; model test; soil pressure; swelling deformation

Address
Zheng Lu: State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China;
Hubei Key Laboratory of Geo-Environmental Engineering, Wuhan 430071, People's Republic of China
Chuxuan Tang, Yu Qiu and Yang Zhao: 1State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics,
Chinese Academy of Sciences, Wuhan 430071, People's Republic of China;
University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
Hailin Yao: State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China
Jianbo She: Jinke property group Hubei Co. Ltd, Wuhan 430063, People's Republic of China
Ming Cheng: Jilin Provincial Transport Scientific Research Institute, Changchun 130012, People's Republic of China


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2022 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-2-736-6800 (SCS, EAS, WAS, ANR) +82-42-828-7995 (GAE, SEM, SSS, CAC) Fax : +82-2-736-6801, Email: info@techno-press.com