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CONTENTS
Volume 8, Number 1, January 2015
 

Abstract
This paper presents a series of conventional undrained triaxial compression tests conducted to determine the effect of both tire crumbs and cement addition on Narli sand specimens. The tire crumb contents and cement contents were 3%, 7%, 15%; and 1%, 3%, 5% by dry weight of the sand specimens respectively. Specimens were prepared at about 35% relative density, cured during overnight (about 17 hours) for artificially bonding under a 100 kPa effective stress (confining pressure of 500 kPa with a back pressure of 400 kPa), and then sheared. Deviatoric stress-axial strain, pore water pressure-axial strain behavior, and Young's modulus of the specimens at various mixture ratios of tire crumb/cement/sand were measured. Test results indicated that the addition of tire crumb to sand decreases Young's modulus, deviatoric stress and brittleness, and increase pore water pressure generation. The addition of cement to sand with tire crumbs increases deviatoric stress, Young's modulus, and changes its ductile behavior to a more brittle one. The results suggest that specimen formation in the way used here could reduce the tire disposal problem in not only economically, and environmentally, but also more effectively beneficial way for some geotechnical applications.

Key Words
sand; tire crumbs; cement; triaxial testing

Address
(1) Zuheir Karabash, Ali Firat Cabalar:
Department of Civil Engineering, University of Gaziantep, 27310, Gaziantep, Turkey;
(2) Zuheir Karabash:
College of Engineering, University of Mosul, Mosul, Iraq.

Abstract
An experimental program was performed to study the effects of cement stabilization on the geotechnical characteristics of sandy soils. Stabilizing agent included lime Portland cement, and was added in percentages of 2.5, 5 and 7.5% by dry weight of the soils. An analysis of the mechanical behavior of the soil is performed from the interpretation of results from unconfined compression tests and direct shear tests. Cylindrical and cube samples were prepared at optimum moisture content and maximum dry unit weight for unconfined compression and direct shear tests, respectively. Samples were cured for 7, 14 and 28 days after which they were tested. Based on the experimental investigations, the utilization of cemented specimens increased strength parameters, reduced displacement at failure, and changed soil behavior to a noticeable brittle behavior.

Key Words
lime portland cement; stabilization; unconfined compressive strength; shear strength parameters; brittle behavior

Address
Department of Civil Engineering, Faculty of Civil Engineering, Babol University of Technology, Iran.

Abstract
Based on the Mohr-Coulomb failure criterion, a gradient-dependent plastic model that considers the strain-softening behavior is presented in this study. Both triaxial shear tests on conventional specimen and precut-specimen, which were obtained from an ancient landslide, are performed to plot the post-peak stress-strain entire-process curves. According to the test results of the soil strength, which reduces from peak to residual strength, the Mohr-Coulomb criterion that considers strain-softening under gradient plastic theory is deduced, where strength reduction depends on the hardening parameter and the Laplacian thereof. The validity of the model is evaluated by the simulation of the results of triaxial shear test, and the computed and measured curves are consistent and independent of the adopted mesh. Finally, a progressive failure of the ancient landslide, which was triggered by slide of the toe, is simulated using this model, and the effects of the strain-softening process on the landslide stability are discussed.

Key Words
gradient plastic theory; triaxial shear test; landslide; strain localization; progressive failure

Address
MOE Key Laboratory of Disaster Forecast and Control in Engineering, College of Science and Engineering, Jinan University, Guangzhou, 510632, PR China.

Abstract
Plastic wastes, particularly polyethylene terephthalate (PET) generated from used bottled water constitute a worldwide environmental issue. Reusing the PET waste for geotechnical applications not only reduces environmental burdens of handling the waste, but also improves inherent engineering properties of soil. This paper investigated factors affecting shear strength improvement of PET-mixed residual soil. Four variables were considered: (i) plastic content; (ii) plastic slenderness ratio; (iii) plastic size; and (iv) soil particle size. A series of unconfined compression tests were performed to determine the optimum configurations for promoting the shear strength improvement. The results showed that the optimum slenderness ratio and PET content for shear strength improvement were 1:3 and 1.5%, respectively. Large PET pieces (i.e., 1.0 cm2) were favorable for fine-grained residual soil, while small PET pieces (i.e., 0.5 cm2) were favorable for coarse-grained residual soil. Higher shear strength improvement was obtained for PET-mixed coarse-grained residual soil (148%) than fine-grained residual soils (117%). The orientation of plastic pieces in soil and frictional resistance developed between soil particles and PET surface are two important factors affecting the shear strength performance of PET-mixed soil.

Key Words
Polyethylene terephthalate (PET); plastic waste; soil improvement; stress strain behavior; unconfined compressive strength

Address
(1) Jian-Jun Zhao, Min-Lee Lee:
State Key Laboratory of Geohazard Prevention and Geoenvironment Protection (Chengdu University of Technology), Number 1, Erxianqiao East 3 road, Chengdu, China;
(2) Min-Lee Lee, Siong-Kang Lim, Yasuo Tanaka:
Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Kuala Lumpur, Malaysia.

Abstract
This article presents the result of laboratory study conducted on expansive soil specimens treated with lignin, rice husk powder (RHP) and rice husk ash (RHA). The amount of lignin produced from paper industry and RHP were varied from 0 to 20% and RHA from 0 to 10% by weight. The treated specimens were subjected to unconfined compressive strength (UCS),swelling test and Atterberg limit tests. The effect of additives on UCS and atterberg limit test results were reported. It was observed that the additives and curing duration had a significant effect on the strength value of treated specimens. Generally (except the sample treated with 20% RHP for 3-day) with increasing additive and curing duration the UCS value increases. A RHP content of 15% was found to be the optimum with regard to 3-day cure UCS.

Key Words
lignin; rice husk powder (RHP); rice husk ash (RHA); unconfined compressive strength (UCS); Atterberg limits; swelling

Address
Department of Civil Engineering, University of Gaziantep, University road, Sehitkamil, Gaziantep, 27310, Turkey.

Abstract
The permeability co behavior of Ariake clays has been investigated by constant rate of strain (CRS) consolidation tests with vertical or radial drainage. Three types of Ariake clays, namely undisturbed Ariake clay samples from the Saga plain, Japan (aged Ariake clay), clay deposit in shallow seabed of the Ariake Sea (young Ariake clay) and reconstituted Ariake clay samples using the soil sampled from the Saga plain, were tested. The test results indicate that the deduced permeability in the horizontal direction (kh) is generally larger than that in the vertical direction (kv). Under odometer condition, the permeability ratio (kh/kv) increases with the vertical strain. It is also found that the development of the permeability anisotropy is influenced by the inter-particle bonds and clay content of the sample. The aged Ariake clay has stronger initial inter-particle bonds than the young and reconstituted Ariake clays, resulting in slower increase of kh/kv with the vertical strain. The young Ariake clay has higher clay ntent than the reconstituted Ariake clay, resulting in higher values of kh/kv. The microstructure of the samples before and after the consolidation test has been examined qualitatively by scanning electron microscopy (SEM) image and semi-quantitatively by mercury intrusion porosimetry (MIP) tests. The SEM images indicate that there are more cut edges of platy clay particles on a vertical plane (with respect to the deposition direction) and there are more faces of platy clay particles on a horizontal plane. This tendency increases with the increase of one-dimensional (1D) deformation. MIP test results show that using a sample with a larger vertical surface area has a larger cumulative intruded pore volume, i.e., mercury can be intruded into the sample more easily from the horizontal direction (vertical plane) under the same pressure. Therefore, the permeability anisotropy of Ariake clays is the result of the anisotropic microstructure of the clay samples.

Key Words
CRS test; inter-particle bonds; microstructure; MIP test; permeability anisotropy; SEM test

Address
(1) Jinchun Chai, Jixiang Nie, Kosuke Aiga, Takehito Negami:
Department of Civil Engineering and Architecture, Saga University, 1 Honjo-machi, Saga 840-8502, Japan;
(2) Rui Jia:
School of Civil Engineering, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China;
(3) Takenori Hino:
Institute of Lowland and Marine Research, Saga University, 1 Honjo-machi, Saga 840-8502, Japan.

Abstract
The kinematical approach of limit analysis is used to estimate the three dimensional stability analysis of rock slopes with nonlinear Hoek-Brown criterion under earthquake forces. The generalized tangential technique is introduced, which makes limit analysis apply to rock slope problem possible. This technique formulates the three dimensional stability problem as a classical nonlinear programming problem. A nonlinear programming algorithm is coded to search for the least upper bound solution. To prove the validity of the present approach, static stability factors are compared with the previous solutions, using a linear failure criterion. Three dimensional seismic and static stability factors are calculated for rock slopes. Numerical results of indicate that the factors increase with the ratio of slope width and height, and are presented for practical use in rock engineering.

Key Words
Hoek-Brown criterion; limit analysis; rock slope; three dimensions

Address
(1) X.L. Yang:
School of Civil Engineering, Central South University, Hunan 410075, China;
(2) Q.J. Pan:
Joseph Fourier University, LTHE UMR 5564, Grenoble, France.

Abstract
In this study, lime (L), silica fume (SF), and lime-silica fume (L-SF) mix have been used for stabilizing and considering their effects on the soft clay soil. The improvement technique adopted in this study includes improving the behaviour of a square footing over soft clay through grouting the clay with a slurry of lime-silica fume before and after installation of the footing. A grey-colored densified silica fume is used. Three percentages are used for lime (2%, 4% and 6%) and three percentages are used for silica fume (2.5%, 5%, 10%) and the optimum percentage of silica fume is mixed with the percentages of lime. Several tests are made to investigate the soil behaviour after adding the lime, and silica fume. For grouting the soft clay underneath and around the footing, a 60 ml needle was used as a liquid tank of the lime-silica fume mix. Slurried silica fume typically contains 40 to 60% silica fume by mass. Four categories were studied to stabilize soft clay before and after footing construction and for each category, the effectiveness of grouting was investigated; the effect of injection hole spacing and depth of grout was investigated too.It was found that when the soft clay underneath or around a footing is injected by a slurry of lime-silica fume, an increase in the bearing capacity in the range of (6.58-88)% is obtained. The footing bearing capacity increases with increase of depth of grouting holes around the footing area due to increase in L-SF grout. The grouting near the footing to a distance of 0.5 B is more effective than grouting at a distance of 1.0 B due to shape of shear failure of soft clay around the footing.

Key Words
soft clay; stabilization; lime-silica fume; grouting

Address
(1) Mohammed Y. Fattah:
Building and Construction Engineering Department, University of Technology Baghdad, Iraq;
(2) A'amal A. Al-Saidi, Maher M. Jaber:
Department of Civil Engineering, College of Engineering, University of Baghdad, Baghdad, Iraq.


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