岩土工程技术

Field-testing and Research on Lime-swelling Subgrade Dynamic Response

TIAN Hai-bo, ZHAO Chun-yan

2006, 20(2): 55-57,62.

[Abstract](39) [PDF 270KB](7)

Abstract:
Through in-situ test on the test plot of lime-swelling soil filled subgrade for the high-speed railway from Hefei to Nanjing, the dynamic response of the subgrade under different velocity is researched by simulating and field-testing the deformation and accelerate caused by running trains in different speed. By testing the deformation, accelerate and dynamic strain on different plots, the distribution law of the deformation,accelerate and dynamic strain is found. It is revealed that the value from the existed code is not reasonable, so a new fixable value for over 200km/h railway is obtained which given reference to the design of new-build high speed railroad.

Application of ObjectARX in Soil Nailing CAD System

ZHENG Jun-jie, LI Qiang, CHEN Jian

2006, 20(2): 58-62.

[Abstract](40) [PDF 504KB](7)

Abstract:
The process of soil nailing CAD systern based on database is illustrated, and the basic knowledge about ObjectARX is introduced. The construction drawings of soil nailing which conform to the practical custom are produced by the successful operation on graphic database. The one-dimensional Brent method and golden section are adopted to search the failure surface automatically. Not only the requirement of the computing speed is met but also the slope analysis of the construction stage is achieved.

Evaluation of Sand Liquefaction Based on SOFM Neural Network

XUE Xin-hua

2006, 20(2): 63-66,102.

[Abstract](47) [PDF 423KB](5)

Abstract:
An improved algorithm for self-organizing feature map neural network is presented. In this algorithm,the expert experience and actual state are considered using training weight vectors, the Gauss weight neighborhood function is used to replace the square or circular function, and different descending functions of learning rate and neighborhood width are used in two learning periods. The improved algrithm is used to evaluate the sand liquefaction. The testing results of practical examples show that the method based on SOFM neural network is feasible and effective, and it provides a new approach to research sand liquefaction potential.

Application of Grounderwater Multi-tracer Test in Karst Area

LIU Xing-yun, CENG Zhao-jian

2006, 20(2): 67-70.

[Abstract](29) [PDF 496KB](5)

Abstract:
Based on a multi-tracer test,the application of the test and the analysis method is introduced. And it is useful for the study of the correlation of the flows of groundwater and the evaluation of hydrogcological condition in Karst region.

New Thinking in Effective Highway Tunnel CAD Design Software

ZHOU Jian-hui, ZHU He-hua, LIU Xue-zeng

2006, 20(2): 71-73,76.

[Abstract](30) [PDF 532KB](6)

Abstract:
Based on the studies into existing highway tunnel CAD design software, and the requirements from practical highway tunnel design, some new solutions for CAD design software is presented. Firstly, to combine parametric based design and interactive design together in modeling and drawing. Secondly, to integrate the three subsystems together, which are structure calculation, structure optimization and construction drawings automatically generating. These solutions are applied in a highway tunnel design software and proved right. The software is developed on GeoFBA2D platform, and provides following features: parametric drawing and interactive drawing, updating drawing right on modification of parameters, FEM calculating considering construction stage, provides several optimizing algorithms and visual drawing management. Highway tunnel design, calculating, optimization and drawing can be completed in a integrated environment, so that highway tunnel design can be more efficiently.

Influence Analysis of Load Cell Position in Osterberg Pile Testing Technique

YANG Zhong, NAI Lei

2006, 20(2): 74-76.

[Abstract](20) [PDF 290KB](6)

Abstract:
The influence of load cell position on bearing capacity of 3 piles using Osterberg pile testing technique is analyzed. with their predicted values, h is found that when the load cell is positioned high or low to the bottom of the pile, the obtained bearing capacity is lower than the actual value. A suitable method is presented. The simulation test method, which bases on classical Mohl- Colum intensity theory and the friction simulation test between the pile and the ground, help to get the optimum position. The conclusion drawn from the method is more accurate than the other two methods.

Study on the Inverted Construction Method of Especially Big Pit Considering the Interaction Between Foundation and Structure

YE Chao-han, YUAN Ju-yun, ZHONG Yi-wei

2006, 20(2): 77-79.

[Abstract](24) [PDF 513KB](9)

Abstract:
Considering the obvious decrease of the pit bottom bounce capacity and differential settlement, the inverted construction method is widely used. It can validly control the distortion of pits, thinking over the interaction between foundation and upside structure in pit digging. The applications of interaction theory in inverted construction method is indicated by analyzing one example of an especially big dip.

Bending Moment Analysis to Underground Diaphragm Wall Based on Crack Control Theory

SHI Shi-yong, LIU Tao

2006, 20(2): 80-83.

[Abstract](53) [PDF 196KB](5)

Abstract:
Based on the theory of the design of crack control and the crack control limit value, an equation to calculate concrete diaphragm wall's bending moment is deduced. Combining with the engineering example the discuss about the effect relationship between the reinforcement ratio and the limit bending moment and the load short term effect bending moment of underground diaphragm wall is made detailedly under w_lim=0.2 and w_lim=0.3, the conclusion of not only crack control requirement but also ultimate bearing capacity requirement can be met if you design the underground diaphragrn wall according to the theory of the design of crack control.

Nonlinear Finite Element Analysis of Vertical Settlement of Reinforced Road Embankment

LIU Jin-long, XIA Hui

2006, 20(2): 84-87.

[Abstract](61) [PDF 479KB](5)

Abstract:
The influence of geotextile on vertical settlement of road embankment is studied with nonlinear finite element method. By comparative computing of the unreinforced road embankment with reinforced one, it is shown that road embankment on soft soil foundation can be reinforced with geotextile effectively when the width of road is small. With that conditions, the vertical increment displacement can be reduced with geotextile, and the vertical displacement can be decreased 12% -16%, the stability of road can be increased more than 20%. While the width of road increased, the influence of geotextile on the vertical settlement of road embankment decreased, which regarded as dimension effect. Therefore, whether geotextile can minish vertical settlement of road embankment or not should be analyzed with reality condition. Furthermore, the limitation of conventional limit equilibrium method in studying embankment reinforced with geotextile is analyzed. It is necessary to develop nonlinear finite element method in studying on the interaction of soil and geotextile.

Study on Slip Band of Carbon Mudstone Landslide in Coal Measure Strata

LI Yu-shu, LI Tian-bin

2006, 20(2): 88-90,93.

[Abstract](28) [PDF 346KB](5)

Abstract:
The variation procedure of material components from the original carbon mudstone to the slip band of the landslide in coal measure strata is studied by analysis of chemical constitution, X-ray diffraction and infra-red spectrum absorption, and then the ultimate cause for the distinct difference in mechanical properties under the condition of dry and soakage between the two kinds of related materials is given. Finally, on the basis of the results of grouped quick shear tests on the remolding slip band soil samples, this paper discusses the correlation between moisture content, dry density and the shear strength parameters, and gives the empirical formulas with practical value.

Study on Vertical Bearing Capacity of Post-injecting Paste Bored Pile

LI Lian-ying, LEI Gang, LIU Dong

2006, 20(2): 91-93.

[Abstract](47) [PDF 281KB](7)

Abstract:
Through analysing several results of static loading test of bored pile which injected paste to pile tip after pile driving, a method of estimating for the standard vertical limited bearing capacity of single pile is presented in Tianjin area.

Calculated Method of Soil Pressure in Deep Pit Engineering Considering Deformation

LIU Qing

2006, 20(2): 94-97.

[Abstract](40) [PDF 187KB](6)

Abstract:
On the basis of present research on the soil pressure with deformation, a new method calculating soil pressure considering deformation is presented. The two typical cases are calculated by the finite element program, the results show that soil pressure at the active zone is between soil pressure at rest and Rankine active soil pressure; and soil pressure at the passive zone is maaller than Rankine passive soil pressure.

Realization of the Joint-arch Bracing System in an Excavation Supporting Project

LI Lai-ming, GONG Xi-qing, WU Yong-hong

2006, 20(2): 98-102.

[Abstract](23) [PDF 577KB](5)

Abstract:
Application of joint arch bracing system in foundation excavations in Tianjin is introduced. joint-arch bracing system is successful in this project.

Behavior of Geosynthetics in Pile-supported and Geosynthetic-reinforced Embankments

JIA Ning, GAO Wen-long

2006, 20(2): 103-106.

[Abstract](27) [PDF 188KB](4)

Abstract:
The subsoil and the embankment treated by a single pile are simplified as a circular column. Considering the soil arching effect, an analytical study is conducted to investigate pile-soil-geosynthetics interactions. Theoretical solution suggests that the inclusion of geosynthetics in the fill enhances the pile efficacy and reduces the differential settlement when the soil arch is in plastic state; when the soil arch is in elastic state, there is no much difference between the cases with or without the geosynthetics. When the ratio of the geosynthetics stiffness to the soft ground stiffness is small, the geosynthetics has little effect in reducing the maximum settlement midway between the pile caps. Finally, these formulas are employed to analyze a set of full-scale model tests and a practical case.

Treatment and Precaution against Constructing Problem of a Pile Foundation Project

KONG Xiang-jun, WEI Jian-hua, LI Liang-jie

2006, 20(2): 107-109.

[Abstract](48) [PDF 137KB](6)

Abstract:
The constructing technology of infixing reinforcing cage after cast-in-place gun-concreting pile by auger rig is used for execution of the pile foundation project. The phenomena of no-designed elevation infixed reinforcing cage and built up in the hole are appeared in the construction. The reason for the phenomena is analyzed, and treatment and precaution is put forward.

2006 Vol. 20, No. 2