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CONTENTS
Volume 12, Number 2, February 2017
 

Abstract
With the rapid development of urban underground traffic, the study of soil deformation induced by subway tunnel construction and its settlement prediction are gradually of general concern in engineering circles. The law of soil displacement caused by shield tunnel construction of adjacent buildings is analyzed in this paper. The author holds that ground surface settlement based on the Gauss curve or Peck formula induced by tunnel excavation of adjacent buildings is not reasonable. Integrating existing research accomplishments, the paper proposed that surface settlement presents cork distribution curve characters, skewed distribution curve characteristics and normal distribution curve characteristics when the tunnel is respectively under buildings, within the scope of the disturbance and outside the scope of the disturbance. Calculation formulas and parameters on cork distribution curve and skewed distribution curve were put forward. The numerical simulation, experimental comparison and model test analysis show that it is reasonable for surface settlement to present cork distribution curve characters, skewed distribution curve characteristics and normal distribution curve characteristics within a certain range. The research findings can be used to make effective prediction of ground surface settlement caused by tunnel construction of adjacent buildings, and to provide theoretical guidance for the design and shield tunnelling.

Key Words
shield tunnel; adjacent structure; surface settlement; cork distribution; skewed

Address
Department of Civil Engineering, Zhejiang University City College, Hangzhou, China.

Abstract
This paper focuses on the regularization of structural configurations by employing meta-heuristic optimization algorithms such as Particle Swarm Optimization (PSO) and Biogeography-Based Optimization (BBO). The regularization of structural configuration means obtaining a structure whose members have equal or almost equal lengths, or whose member\'s lengths are based on a specific pattern; which in this case, by changing the length of these elements and reducing the number of different profiles of needed members, the construction of the considered structure can be made easier. In this article, two different objective functions have been used to minimize the difference between member lengths with a specific pattern. It is found that by using a small number of iterations in these optimization methods, a structure made of equal-length members can be obtained.

Key Words
structural configuration; regularization; optimization; meta-heuristic; configuration processing

Address
Department of Civil Engineering, Iran University of Science and Technology, Narmak, Tehran, Iran.

Abstract
A laboratory investigation into crude oil contaminated sand-concrete interface behavior is performed. The interface tests were carried out through a direct shear apparatus. Pure sand and sand-bentonite mixture with different crude oil contents and three concrete surfaces of different textures (smooth, semi-rough, and rough) were examined. The experimental results showed that the concrete surface texture is an effective factor in soil-concrete interface shear strength. The interface shear strength of the rough concrete surface was found higher than smooth and semi-rough concrete surfaces. In addition to the texture, the normal stress and the crude oil content also play important roles in interface shear strength. Moreover, the friction angle decreases with increasing crude oil content due to increase of oil concentration in soil and it increases with increasing interface roughness.

Key Words
sand-concrete interface; pollution; shear strength; bentonite

Address
Department of Civil and Environmental Engineering, Amirkabir University of Technology, 424 Hafez Ave, Tehran, Iran.

Abstract
In this study, bearing capacities and settlement profiles of six irregularly shaped footings located on sand have been experimentally and analytically investigated under the effect of axial loading. The main variable considered in the study was the geometry of the footings. The axial loads were applied from the center of gravities of the test specimens. Consequently, the effect of footing shape on the variation of the bearing capacities and settlement profiles have been investigated in this paper. The three dimensional finite element analyses of the test specimens were conducted using the PLAXIS 3D software. The finite element model results are in acceptable agreement with the results obtained using experimental investigation. In addition, the usability of the finite element technique by design engineers to determine the bearing capacities and settlement profiles of irregularly shaped footings was investigated. From the results of the study, it was observed that the geometric properties of the footings significantly influenced the variation of the bearing capacities and settlement profiles.

Key Words
bearing capacity of foundation; shape factor; settlement profile; finite element analysis; geometry of footing

Address
Civil Engineering Department, Gazi University, Maltepe, Ankara 06570, Turkey.

Abstract
Various centrifuge model tests on the pile foundations were performed to investigate fundamental characteristics of a pile-soil-foundation system recently, but it is hard to find numerical analysis results of a pile foundation system considering the nonlinear behavior of soil layers due to the dynamic excitations. Numerical analyses for a pile-soil system were carried out to verify the experimental results of centrifuge model tests. Centrifuge model tests were performed at the laboratory applying 1.5Hz sinusoidal base input motions, and nonlinear numerical analyses were performed utilizing a finite element program of P3DASS in the frequency domain and applying the same input motions with the intensities of 0.05 g~0.38 g. Nonlinear soil properties of soil elements were defined by Ramberg-Osgood soil model for the nonlinear dynamic analyses. Nonlinear numerical analyses with the P3DASS program were helpful to predict the trend of experimental responses of a centrifuge model efficiently, even though there were some difficulties in processing analytical results and to find out unintended deficits in measured experimental data. Also nonlinear soil properties of elements in the system can be estimated adequately using an analytical program to compare them with experimental results.

Key Words
complex centrifuge model test; pile foundation; P3DASS program; sinusoidal base input motion; nonlinear numerical analysis; Ramberg-Osgood soil model

Address
(1) Yong-Seok Kim:
Department of Architectural Engineering, Mokpo National University, 58554, Republic of Korea;
(2) Jung-In Choi:
Pangyo R&D Center, Samsung Heavy Industry, Pangyo, Bundang, Seongnam, Gyeonggi, 13486, Republic of Korea.

Abstract
This paper presents laboratory investigation of stabilization of subgrade soil. One type of soil and three types of stabilizers i.e., hydrated lime, class F fly ash and polypropylene fibres are selected in the study. Atterberg limit, compaction, california bearing ratio (CBR), unconfined compressive strength and triaxial shear strength tests are conducted on unstabilized and stabilized soil for varying percentage of stabilizers to analyze the effect of stabilizers on the properties of soil. Vertical compressive strains at the top of unstabilized and stabilized subgrade soil were found out by elasto-plastic finite element analysis using commercial software ANSYS. Strategy for design of optimum pavement section was based on extension in service life (TBR) and reduction in layer thickness (LTR). Extension in service life of stabilized subgrade soil is 6.49, 4.37 and 3.26 times more due to lime, fly ash and fibre stabilization respectively. For a given service life of the pavement, there is considerable reduction in layer thicknesses due to stabilization. It helps in reduction in construction cost of pavement and saving in natural resources as well.

Key Words
California bearing ratio; stabilization; subgrade; layer thickness reduction; traffic benefit ratio

Address
(1) Prashant P. Nagrale:
Civil Engineering, Sardar Patel College of Engineering, Mumbai, India;
(2) Atulya P. Patil:
Department of Civil Engineering, Sardar Patel College of Engineering, Mumbai, India.

Abstract
This study aimed to realize the creation of fuzzy stochastic damage to describe reliability more essentially with the analysis of harmony of damage conception, probability and fuzzy degree of membership in interval [0,1]. Two kinds of fuzzy behaviors of damage development were deduced. Fuzzy stochastic damage models were established based on the fuzzy memberships functional and equivalent normalization theory. Fuzzy stochastic damage finite element method was developed as the approach to reliability simulation. The three-dimensional fuzzy stochastic damage mechanical behaviors of Jianshan mine slope were analyzed and examined based on this approach. The comprehensive results, including the displacement, stress, damage and their stochastic characteristics, indicate consistently that the failure foci of Jianshan mine slope are the slope-cutting areas where, with the maximal failure probability 40%, the hazardous Domino effects will motivate the neighboring rock bodies' sliding activities.

Key Words
fuzziness; stochastics; rock slope; damage; reliability

Address
School of Maritime and Civil Engineering, Zhejiang Ocean University, 1# Southern Road of Haida, Changzhi Island, Lincheng New District, Zhoushan City, Zhejiang Province, P.R. China.

Abstract
Cast in situ and grouted concrete helical piles with 150-200 mm diameter half cylindrical ribs have become an economical and effective choice in Shanghai, China for uplift piles in deep soft soils. Though this type of pile has been successful used in practice, the reinforcing mechanism and the contribution of the ribs to the total resistance is not clear, and there is no clear guideline for the design of such piles. To study the inclusion of ribs to the contribution of shear resistance, the shear behaviour between silty sand and concrete slabs with parallel ribs at different spacing and angles were tested in a large direct shear box (600 mm × 400 mm × 200 mm). The front panels of the shear box are detachable to observe the soil deformation after the test. The tests were modelled with threedimensional finite element method in ABAQUS. It was found that, passive zones can be developed ahead of the ribs to form undulated failure surfaces. The shear resistance and failure mode are affected by the ratio of rib spacing to rib diameter. Based on the shape and continuity of the failure zones at the interface, the failure modes at the interface can be classified as "punching", "local" or "general" shear failure respectively. With the inclusion of the ribs, the pull out resistance can increase up to 17%. The optimum rib spacing to rib diameter ratio was found to be around 7 based on the observed experimental results and the numerical modelling.

Key Words
soil and ribbed concrete interface resistance; cast in-situ concrete helical piles; optimum rib spacing; undulated shear failure surface

Address
(1) Jian-Gu Qian, Qian Gao, Mao-Song Huang:
Department of Geotechnical Engineering, Tongji University, Shanghai, 200092, China;
(2) Jian-feng Xue:
School of Engineering and IT, Federation University, Churchill, 3842, VIC, Australia;
(3) Hong-Wei Chen:
Department of Underground Structure & Geotechnical Engineering, East China Architecture Design & Research Institute Co., Ltd., Shanghai 200002, China.

Abstract
Based on the reliability theory and limit analysis method, the roof stability of a shallow tunnel is investigated under the condition of surface settlement. Nonlinear Hoek-Brown failure criterion is adopted in the present analysis. With the consideration of surface settlement, the internal energy and external work are calculated. Equating the rate of energy dissipation to the external rate of work, the expression of support pressure is derived. With the help of variational approach, a performance function is proposed to reliability analysis. Improved response surface method is used to calculate the Hasofer-Lind reliability index and the failure probability. In order to assess the validity of the present results, Monte-Carlo simulation is performed to examine the correctness. Sensitivity analysis is used to estimate the influence of different variables on reliability index. Among random variables, the unit weight significantly affects the reliability index. It is found that the greater coefficient of variation of variables lead to the higher failure probability. On the basis of the discussions, the reliability-based design is achieved to calculate the required tunnel support pressure under different situations when the target reliability index is obtained.

Key Words
shallow tunnel; surface settlement; reliability analysis

Address
School of Civil Engineering, Central South University, Hunan 410075, China.

Abstract
Laminated plates have many applications in different industrials. Buckling analysis of these structures with the nano-scale reinforcement has not investigated yet. However, buckling analysis of embedded laminated plates with nanocomposite layers is studied in this paper. Considering the single-walled carbon nanotubes (SWCNTs) as reinforcement of layers, SWCNTs agglomeration effects and nonlinear analysis using numerical method are the main contributions of this paper. Mori-Tanaka model is applied for obtaining the equivalent material properties of structure and considering agglomeration effects. The elastic medium is simulated by spring and shear constants. Based on first order shear deformation theory (FSDT), the governing equations are derived based on energy method and Hamilton's principle. Differential quadrature method (DQM) is used for calculating the buckling load of system. The effects of different parameters such as the volume percent of SWCNTs, SWCNTs agglomeration, number of layers, orientation angle of layers, elastic medium, boundary conditions and axial mode number of plate on the buckling of the structure are shown. Results indicate that increasing volume percent of SWCNTs increases the buckling load of the plate. Furthermore, considering agglomeration effects decreases the buckling load of system. In addition, it is found that the present results have good agreement with other works.

Key Words
buckling of laminated plates; SWCNT; agglomeration effects; DQM; elastic medium

Address
Buein Zahra Technical University, Buein Zahra, Qazvin, Iran.


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