岩土工程技术

The Most Reliable Method to Expose Trenchless Underground Rock Mass Structure High Precise Ultrasonic Logging

Li Yin, Shen Maoding, Xu Huawen

2011, 25(2): 55-58,67. doi: 10.3969/j.issn.1007-2993.2011.02.001

[Abstract](51) [PDF 670KB](8)

Abstract:
Taking for example the ultrasonic logging imaging in one crossing engineering investigation of Yangtze River, and combined with other cases of high precise ultrasonic logging in China, then compared with traditional investigation technique and other logging imagings, this paper aims at analysising the advantage of new ultrasonic logging tool, such as in the aspect of the description of bedrock weathering zone and the estimation of rock quality designation. Especially in the aspect of precisely exposing rock fractures of underground rock mass structure, high precise ultrasonic logging imaging can provide large quantities of effective and apparent data rock mass around borehole, and these data are very good basis for the quantitative analysis of engineering design and point out one effective access to improve the technological level of geotechnical investigation, at the same time proving itself the most reliable method to expose trenchless underground rock mass structure up to now.

The Research and Application of Multi-casting Drilling Technology to Hydropower Engineering Investigation

Li Zhiyuan, Huang Xiaojun

2011, 25(2): 59-63. doi: 10.3969/j.issn.1007-2993.2011.02.002

[Abstract](57) [PDF 686KB](4)

Abstract:
Exploration for construction of hydropower projects in recent years, the problems encountered in the analysis and research. First discuss the modified plant gum and application of irrigation fluid; and then focus on the drill pipe drilling process with a large landslide in the exploration, through river dam axis slant-hole drilling exploration and deal with accidents, etc. buried hole wide range of applications. Practical application of this technology is much higher than the traditional process with the possession, not only improve the overall level of drilling, but also has a good application and popularization.

Application of p-s Curve in the Analysis of Bernoulli-Euler Beam on Non-linear Elasticity Foundation

Niu Wenjie

2011, 25(2): 64-67. doi: 10.3969/j.issn.1007-2993.2011.02.003

[Abstract](41) [PDF 493KB](4)

Abstract:
Under large load, plastic deformations occur in foundation soil below Bernoulli-Euler girder. Linear algebra equations were derived after the Winkler foundation beam governing equations were discretized with Finite Difference Method. Computer program Fortran was called to solve these equations. Then by p-s curve through iterative computations, beam deflection considering subgrade reaction coefficient variation with Load was obtained with Finite Difference Method. Results indicate that by p-s curve and Winkler foundation beam model considering subgrade reaction coefficient variation with load, one can approximately judge whether supporting ground soil is in elastic stage or elastoplastic stage, and the deflection can be determined relatively properly. At last, the application scope of this method is discussed.

Experimental Study on One-dimensional Characteristics of Soft Secondary Consolidation Clay

Shen Daqing, Yu Yongtang, Hou Xiaoliang

2011, 25(2): 68-71. doi: 10.3969/j.issn.1007-2993.2011.02.004

[Abstract](45) [PDF 535KB](7)

Abstract:
Based on a series of 1D secondary consolidation tests for natural and remolded soft clay samples at Hexi region in Nanjing, the pre-pressure, the load ratios and the loading methods on secondary consolidation properties of remolded samples and deformation characteristics of the natural samples have been researched. The results show that the pre-consolidation pressure can significantly reduce the secondary consolidation coefficient when the consolidation pressure is less than pre-pressure. Otherwise, the effect of pre-pressure on the secondary consolidation coefficient is not obvious. Increase of the load ratios is able to increase the secondary consolidation coefficient. The corresponding secondary consolidation coefficient of the step loading is greater than the separate loading. The creep deformation of natural samples in the region has the character of decay slowly.

Study on Duncan-Chang Model and Strain Hardening Index Theory of Soft Dredger Fill

Zhang Yan, Yang Aiwu, Zhou Jin

2011, 25(2): 72-74,80. doi: 10.3969/j.issn.1007-2993.2011.02.005

[Abstract](50) [PDF 575KB](6)

Abstract:
Large-scale reclamation project is being conducted in Tianjin Binhai New Area. For plentiful fine grain in dredger fill and uncompleted consolidation,the settlement after construction needs to be solved immediately.In thise paper, triaxial tests were performed on the remoulded samples of the soft dredger fill.Based on the analysis of the stress-strain curves derieved from the tests,duncan-chang model and strain hardening theory were compared.The results showed distinctive characteristies of both models:Duncan-Chang model can predict stress-strain curve accurately at the initial and last stage,but strain hardening theory may reflect strain hardening ability for remoulded dredger fill.

Risk Analysis of Tiansan Landslide in Kala Hydropower Station

Ma Cong, Tan Yuehu, He Shihai

2011, 25(2): 75-80. doi: 10.3969/j.issn.1007-2993.2011.02.006

[Abstract](55) [PDF 650KB](3)

Abstract:
Risk analysis of landslide is one of the critical factors for the selection of dam site. Through field investigation and data analysis of Tiansan landslide in Kala hydropower station, risk analysis model is established. With Bayes statistical methods and Monte Carlo method to determine the parameters, considering the combination of rainstorm state, water-storage conditions, earthquake and other conditions, the analysis of stability, surge and river blockage of Tiansan landslide are done. Risk analysis of Tiansan landslide provides experience for failure mechanism in the region, which will facilitate the determining of the dam site selection.

Monitoring Analysis in Stress of “T” Diaphragm Wall in Deep Foundation Pit

Xiao Qinghua

2011, 25(2): 81-85. doi: 10.3969/j.issn.1007-2993.2011.02.007

[Abstract](52) [PDF 678KB](4)

Abstract:
Basted on the monitoring data of a deep foundation pit adopted the "T" Diaphragm wall, this paper illustrates the temperature effect on steel bar gauge measurement. of the "T" Diaphragm wall, and provides amendment coefficients of temperature effect. Through analysis the law of the "T" Diaphragm wall stress in different sections and the corresponding values of moment and axial force, some conclusions and recommendations are given for the similar engineering projects.

Research on Simplified Method to Calculate Foundation Settlement with Vacuum Preloading Method

Li Ning, Li Xiangfeng, Liu Jian

2011, 25(2): 86-89. doi: 10.3969/j.issn.1007-2993.2011.02.008

[Abstract](50) [PDF 548KB](7)

Abstract:
The average of vacuum pressure using the equivalent circle of single well foundation, instead of the average of vacuum pressure of mul ti-boreholes, was applied to specify the method to calculate foundation settlement under k_0 consolidation condition. Founding on the advanced method considering soil lateral displacement to calculate foundation settlement, the paper took new consideration and analysis with the modify coefficient in volumetric strain, and specified the concepts upon the coefficient of average volume stress, also firmly believed that the consolidation settlement considering soil lateral displacement should modify formula by applying the method ofaverage volume strain. Proceeding from finite element analysis, this paper made a comparison between the result of theory analysis, FEM calculation and surveillance. And the result was reasonable and reliable. It was more Reasonable and convenient to apply the method to forecast foundation settlement and it can be a reference to the generalization and application of the designs of vacuum preloading method.

The Influencing Factor Analysis of Pile Ultimate Bearing Capacity of Grouting Pile

Yang Zimin, Kang Xianquan, Bian Shengzhai

2011, 25(2): 90-94. doi: 10.3969/j.issn.1007-2993.2011.02.009

[Abstract](47) [PDF 517KB](8)

Abstract:
With the city developing faster, land is becoming more precious, high——rise buildings are growing rapidly, to meet the growing needs of the structural loads, pile length and pile diameter gets more greate. Without increase in costs, post grouting technique improves bearing capacity of cast——in——place pile, and lowered the settlement of building, it has been more used. This paper introduces the improvement mechanism of post grouting pile and several engineering examples, analysis the change of bearing capacity of single pile grouting before and after grouting, and application accumulated some material.

Research and Analysis of Deformation in Retaining Structures of Deep Foundation Engineering

Zhang Qinxi, Ma Qingxun, Zhang Mingju

2011, 25(2): 95-100. doi: 10.3969/j.issn.1007-2993.2011.02.010

[Abstract](44) [PDF 619KB](4)

Abstract:
With the development of urban underground space,especially the construction of subway,Deep Foundation Pit engineering of deformation and the structure directly affect the project construction cost and the safe use of surrounding buildings. This paper takes deep foundation pit engineering of shenzhen metro line 2 east along of a transfer station - JingTian for example. By the field monitoring and the method of software simulation calculation,Analyze the deformation law of the retaining structure (Diaphragm wall + steel supports) in deep foundation pit construction,Provide the reference for optimization design and scientific construction of deep foundation pit engineering and similar retaining structure of shenzhen area.

Studies on the Construction Sequence of Different Piles in High-speed Railway Yard

Qin Xiaoguang, Yang Longcai, He Taihong

2011, 25(2): 101-105. doi: 10.3969/j.issn.1007-2993.2011.02.011

[Abstract](34) [PDF 599KB](4)

Abstract:
This thesis is focus on the soil compaction effect due to pile installation. There are PHC pile、CFG pile and MMP pile in one of the Shanghai-Nanjing high-speed railway yard. With theoretical simplified method and the Ansys finite analysis program to estimate the distribution and impact ranges on stress and displacement fields of single pile、vertical piles and pile groups. It is concluded that the influences of squeezing effect of PHC pile on surrounding pile is existence. And some reasonable suggestions on construction sequence are given. The studies of this thesis may have some practical effect in engineering practice.

Geological Characteristics and Anti-seepage Evaluation of Municipal Waste Landfill in Huaian

Wang Mingpeng

2011, 25(2): 106-109. doi: 10.3969/j.issn.1007-2993.2011.02.012

[Abstract](25) [PDF 541KB](8)

Abstract:
Correct analysis and evaluation of municipal waste landfill geological characteristics and seepage program play a very important role in municipal waste landfill siting and design and construction operations.The geological characteristics of municipal waste landfill in Huaian city,such as natural environment, Stratigraphic structure and lithology are described,hydrogeological conditions of municipal waste landfill,as well as aquifer distribution, aquifer thickness and permeable are analysed in detail in the paper.On the basis of laboratory test and in-situ tests,comprehensive determined of the strata permeability coefficient greater than 1×10^-7cm/s in municipal waste landfill siting,indicated that does not have natural anti-seepage conditions,must use the artificial anti-seepage system to be able effective to prevent pollution of environment form the leachate of refus.

2011 Vol. 25, No. 2