岩土工程技术

Analysis of Methods for Checking Bearing Capacity of Underlying Weak Layer in Pile Foundation Design

Lei Fenghao, Tian Jingxian, Wang Chenghua

2013, 27(1): 1-4. doi: 10.3969/j.issn.1007-2993.2013.01.001

[Abstract](71) [PDF 631KB](10)

Abstract:
Checking for the bearing capacity of underlying weak layer is an important item in pile foundation desigru The different methods which are suggested in Technical Code for Building Pile Foundations JGJ 94-1994 and JGJ 94-2008 are comparatively analyzed. The self weight of soil above cap and the shaft resistance around the pile group are analyzed. Deficiencies of the methods are found in the two codes, some suggestions are put forward:the former is fit for small-scale pile foundation without basement while the latter is fit for piled box(raft) foundation with basement, the shaft resistance around the pile group should use the characteristic value when calculate the additional stress.

Experimental Study of Local Air-lift Inverse Circulation Rotary Drilling Technology With Large Diameter Hollow-through DTH Hammer

Yi Zhenhua, He Longfei, Hu Zhihai

2013, 27(1): 5-8. doi: 10.3969/j.issn.1007-2993.2013.01.002

[Abstract](48) [PDF 666KB](11)

Abstract:
Through actual drilling tests in the 50 meters wells, the SH25H hydraulic pneumatic impact drill was trial manufactured with the pneumatic DTH and local inverse circulation rotary drilling technology, and continuous footage was ensured by retractable drill pipe. The multi-techniques drilling technique is developed with high drilling efficiency and high quality of borehole.

Field Monitoring Test Analysis of Controlling Settlement for Expressway Soft Foundation by Combined Vacuum Surcharge Preloading Method

Yin Pai, Huang Zuojun, Yuan Xiaolin

2013, 27(1): 9-12,24. doi: 10.3969/j.issn.1007-2993.2013.01.003

[Abstract](33) [PDF 695KB](8)

Abstract:
The combined vacuum surcharge preloading method has the double reinforcement effects of vacuum preloading method and surcharge preloading method. The lateral extrusion deformation due to surcharge preloading was counteracted by the lateral shrinkage induced by vacuum preioading, which ensures the stability of the upper embankment, accelerates the subsoil consolidation and enhances the construction speed. Based on the practical engineering of expressway soft soil treatment, the full monitoring was conducted for the complete and effective observation sections, according to four field test sections. The analyzed results show that the main settlement reinforced by the combined vacuum surcharge preloading method occurs in the early and middle phrase; the settlement and rate is large in the early stage,reaches maximum in the middle stage and becomes little in the last stage; the maximum settlement rate is 0. 09cm/d and less than the allowable value of 1cm/d required by of surcharge preloading method,which indicates that the reinforcement effect of combined vacuum surcharge preloading method is significant.

Numerical Simulation Analysis of CFG Pile Composite Foundation

Fan Chongmin, Wang Hao, Bing Yufeng

2013, 27(1): 13-16,40. doi: 10.3969/j.issn.1007-2993.2013.01.004

[Abstract](52) [PDF 1410KB](8)

Abstract:
It's analyzed that the characters of settlement and stress about CFG pile composite foundation using FLAC^3D program. And it's proved that the FLAC^3D program's dependability in the numerical simulation analysis of CFG pile composite foundation. Advices is offered to the designs and constructions.

Application of Super-Large Ring Concrete Bracing System In Deep Foundation Pit Engineering

Zhao Shengfeng, Fan Qinjian

2013, 27(1): 17-20,28. doi: 10.3969/j.issn.1007-2993.2013.01.005

[Abstract](53) [PDF 699KB](12)

Abstract:
Through a example of deep foundation pit of international R&D headquarters park in science and technology park of Nanjing new city, engineering application characteristics of super-large ring bracing system are analyzed, which diameter is more than 200 meter. The structure design, layout, vertical load-bearing structure, the force and reinforcement calculation of ring are also analyzed. The related structure node and the key technical points are summarized in the designation of super-large ring bracing system. In the site test,the displacement of excavation is small and internal force of bracing system is in the controllable range. The whole construction process is safe and reliable, and protects the surroundings nearby well. The results show that these measures achieve good implementation. It provide some suggestions for same type of deep foundation pit projects.

Study on Foundation Pit Project of Subway Station in Yangtze River Floodplain

Sun Xiaofeng, Fang Zhongqiang

2013, 27(1): 21-24. doi: 10.3969/j.issn.1007-2993.2013.01.006

[Abstract](39) [PDF 626KB](7)

Abstract:
This paper summarizes engineering geological and hydrogeological characteristics of the Yangtze River floodplain in the west river area of Nanjing. And surveied the built subway station foundation pit support scheme and implementation effect, compared the foundation pit support scheme of subway station for the west river area of nanjing, propound targeted measures for common problem. This paper has a certain guiding value for design and construction of subway station pip in this area.

Analysis of Eco-Clay Wall Method and Material Properties

Xu Guangda, Xu Guangli, Li Junjie

2013, 27(1): 25-28. doi: 10.3969/j.issn.1007-2993.2013.01.007

[Abstract](62) [PDF 695KB](4)

Abstract:
It is urgent to develop new sequester seepage wall method to prevent the soil and water pollution problems with the development of urbanization. A new Eco-Clay Wall method, which is developed by Raito Kogyo Co. Ltd., Japan, is introduced herein. The outlines of the new method, characteristics, application and wall material behaviors are described. Compared to the exiting sequester seepage wall methods, it has excellent sequester seepage effect, good service durability, environment-friendly due to the wall is constructed by natural clay material and no dispose soil. The coefficient of permeability of the wall is less than 10^-8 m/s, which can be considered as an impermeable material. The wall shows large ductility, plastic deformation and no shear fracture failure .

Experimental Study on Frost Heaving Behavior of WFS-FA-EPS Fills

Yu Yongtang, Deng An, Yu Qinghua

2013, 27(1): 29-32. doi: 10.3969/j.issn.1007-2993.2013.01.008

[Abstract](48) [PDF 635KB](4)

Abstract:
A cement treated fills was fomed by blending waste foundry sand (WFS),fly ash (FA),expandable polystyrene (EPS) beads,Portland cement and water in proportions. The effects of mixing ratios on the frost heaving deforrmtion of the fills have been studied. The results show that increase of EPS beads content or cement content can reduce the frost heaving deformation of the WFS-FA-EtX3 fills The single factor is changed in the experiment,the frost heaving ratio decrease close to linearity with the increase of the cement content ratio or the EPS beads content ratio, the frost heaving ratio increase close to linearity with the increase d the water content. The thermal conductMty of the fills close to first-order exponential decay with the increase of the EPS beads content ratio under normal temperature; The formed WFS-FA-EPS fills with the characteristics of low density, low thermal conductivity and resistance to frost heaving deformation, which can be used as frost-resistant materials in the roadbed engineering of cold region.

Analysis of Strength Reduction Method Criterion on FLAC-3D

Chen Ran, Liu Fei

2013, 27(1): 33-36. doi: 10.3969/j.issn.1007-2993.2013.01.009

[Abstract](52) [PDF 713KB](4)

Abstract:
FLAC-3D is used to analyze a simple slope The comparative analysis of the safety factors which were calculating by convergence criterion, plastic zone criterion, effective shear strain increment criterion and displacement mutation criterion. By the selection of the "feature points" and "mutations criterion for analysis,The top of the hill and the slope midpoint of displacement monitoring is more effective than detecting the foot of the slope at the displacement; mutations only from the displacement size as a criterion standard is not stringent enough,and propose a feature point by observing the displacement reduction factor curve slope changes determine the safety factor, the slope of the mutation at the corresponding reduction factor is the safety factor.

Influencing Factors of Loess Slope Stability and Analytical Methods

Wang Xiaofeng, Dong Hui, Yu Qinghua

2013, 27(1): 37-40. doi: 10.3969/j.issn.1007-2993.2013.01.010

[Abstract](33) [PDF 489KB](8)

Abstract:
There are many loess gully natural high and steep slopes in Shanxi Province,Slope stability is an extremely important issue in the construction of highways, railways and other projects. If not handled properly, it will result in the loss of human and economy. This paper analyzes the slope failure of external and internal factors, currently used for slope stability analysis are sunmaarized to provide a theoretical basis for slope stability designs of practical engineering, slope stability analysis and slope treatment.

Development and Utilization Analysis of Geothermal Resources in Xinjiang County

Zhang Junxue

2013, 27(1): 41-42,51. doi: 10.3969/j.issn.1007-2993.2013.01.011

[Abstract](21) [PDF 527KB](5)

Abstract:
Xinjiang County is one of the most abundant geothermal areas in Shanxi Province. Based on the analysis of the topographical features of geothermal field geothermal types and regularities of distribution, through the feasibility analysis and research, put forward reasonable development and utilization of geothermal resources countermeasures and suggestions.

Deeply Buried Pipeline Detection Technology Based on Magnetic Gradient Method

Zhan Bin, Zhu Nengfa, Sun Shihui

2013, 27(1): 43-46. doi: 10.3969/j.issn.1007-2993.2013.01.012

[Abstract](50) [PDF 654KB](13)

Abstract:
General pipeline detectos can not solve deeply buried pipeline detection problem. A horizontal cylinder of magnetic anomalies and the magnetic gradient anomalies forward model are established. Through horizontal metal pipes magnetic anomaly vertical cross-sectional view of the magnetic and gradient anomalies vertical cross-sectional view of contrast. The "s" inflection point is of tained to determin pipeline depth discriminant flag, and in the practical application of the desired effect.

Research on Earthwork Calculation of Complex Shapes Foundation Pit Based on GIS

Wang Zengfu, Feng Keming

2013, 27(1): 47-51. doi: 10.3969/j.issn.1007-2993.2013.01.013

[Abstract](35) [PDF 564KB](5)

Abstract:
There are several mature methods of earthwork calculations according to the former study. However, they have advantages and disadvantages due to different applicable conditions and input data types. It's a problem that how to learn the advantages of these methods and take a more data-compatible way to calculate earthwork project. Inheriting the most widely used method of grid principle and the advanced GIS technology, we proposed an earthwork volume calculation method based on GIS raster data. Through the method the grid can switch freely according to the required accuracy, the amount of earth can be quickly and accurately calculated. Also, this paper discussed the impacts of the grid size on earthwork calculation accuracy.

Research on Causes and Treatment Measures of Nantong Binjiang Park HydrophUic Platform Collapse

Jin Shujie

2013, 27(1): 52-55. doi: 10.3969/j.issn.1007-2993.2013.01.014

[Abstract](21) [PDF 627KB](5)

Abstract:
Nantong Binjiang Park hydrophilic platform which is located in Nantong Langshang Scenic Area belongs to Taoyuan dangerous section of Yangtze river. In August 12, 2012, partial collapse of hydrophilic platform happened suddenly and thus made a severe geological disaster. This paper studies the causes of the disaster from the hydrological and geological reasons. Then specific suggestions and treatment measures is given to repair the geological disaster.

2013 Vol. 27, No. 1