岩土工程技术

Application Example of PHC Pipe Piles in Excavation Engineering

Yu Hongan, Wang Zhiyong

2013, 27(6): 271-274,319. doi: 10.3969/j.issn.1007-2993.2013.06.001

[Abstract](30) [PDF 1620KB](6)

Abstract:
The paper analyses application of the PHC pipe piles instead of cast-in-situ bored pile in an excavation,and studies some questions in design rocedure.

Suitability Division for Groundwater Source Heat Pump System Application in Suzhou City

Wang Bin, Gu Fengxiang, Chen Chunming

2013, 27(6): 275-279,309. doi: 10.3969/j.issn.1007-2993.2013.06.002

[Abstract](37) [PDF 1277KB](4)

Abstract:
Taking Suzhou city as the research background to explain the hydrologic geological conditions of the region's shallow geothermal energy resources, analysis of the groundwater source heat pump system applications may impact on the groundwater environment, which shows that Section Ⅱ is the ideal aquifer exploitation confined aquifer for groundwater source heat pump application in this region. On these bases, establish standards of suitability division by the theory of Analytic Hierarchy Process and Comprehensive Index, Suzhou city shallow groundwater source heat pump system application is divided into suitable area, the general suitable area and unsuitable area.This article provide an important basis on shallow groundwater source heat pump system and the development of rational exploitation of groundwater and other environmental protection measures in Suzhou city.

Soil Corrosion Evaluation of a Salt Lake Area

Tan Haijun, Shi Ke

2013, 27(6): 280-283. doi: 10.3969/j.issn.1007-2993.2013.06.003

[Abstract](36) [PDF 461KB](5)

Abstract:
Potassium, sodium, magnesium, lithium, gas and other resources are rich in salt lake area, so comprehensive development and utilization of salt lake resources is getting increasing attention. However, Mg²⁺、Cl^- and SO₄^2- ion content is very high in the soil environment of the salt lake area, which can make serious erosion and damage to concrete and steel. By means of chemical and electrochemical detection, physical and chemical indicators such as soil resistivity, soil salinity, soil pH, chloride ion content and sulfate ion content in several typical locations of the salt lake area are analyzed. Soil causticity in the salt lake area is analyzed and evaluated in accordance with relevant standards, the results show that the salt lake soil belongs to highly corrosive saline soil.

Properties of Soft Soils in Chuhe Floodplain

Zhou Chao

2013, 27(6): 284-287. doi: 10.3969/j.issn.1007-2993.2013.06.004

[Abstract](49) [PDF 490KB](5)

Abstract:
With the continuous development of economic and building scale, it is more and more attractive to utilize the underground space. There is deep soft soil in floodplain of the Chuhe river. With the expansion of the scale of pit, reasonable physical and mechanical parameters will save costs for the pit protection in the promise of safety, which wiu be good for economic benefits and can offer support for establishing a complete evaluation system for regional soft soil. Analysis for properties of the floodplain soft soil and for adverse effects for the soft soil to construction is done. A modified formula for the in situ testing is proposed and thus a new method to calculate the capacity of the soft soil in floodplain with the in situ testing is suggested.

Low Strain Reflected Wave Method in Practice of Pile Testing

Lin Daojun, Liu Jipeng, Han Yanfang

2013, 27(6): 288-291. doi: 10.3969/j.issn.1007-2993.2013.06.005

[Abstract](89) [PDF 872KB](5)

Abstract:
Low strain reflected wave method has been a widely used technology of pile foundation detection recently. In connection with common engineering quality problems in the foundation construction progress, such as broken pile, necking, widening from folding and other problems, this paper illustrates the basic principles of low strain reflected waves law briefly. Meanwhile, combining with the filed data collection and the indoor trail data analysis, it investigates preliminarily the pile detection with the low strain reflected wave method,and it has got a corresponding verification from engineering practice.

Project Case of Pumping Test in Loess Area

Liu Feng

2013, 27(6): 292-295,300. doi: 10.3969/j.issn.1007-2993.2013.06.006

[Abstract](40) [PDF 694KB](8)

Abstract:
In this paper, methods to measure the permeability coefficient and its radius of influence are introduced by a pumping test in loess area.A new method is proposed for the permeability coefficient in loess area and its arrangement of observation wells.This work has some guidance for the excavation dewatering.

Analysis on Liquefaction of Embankment Foundation of Reservoir by Secondary Development of ANSYS

Wu Feng, Li Li

2013, 27(6): 296-300. doi: 10.3969/j.issn.1007-2993.2013.06.007

[Abstract](40) [PDF 2515KB](4)

Abstract:
Based on secondary development of ANSYS, analysis on liquefaction of embankment foundation of a reservoir is performed. Two-dimensional finite element model of representative embankment section is set up, and distribution of ratios of pore water pressure and effective stress before and after the construction of the embankment and distribution of seismic subsidence of the embankment are obtained by calculation. As demonstrated by the calculation results, ratio of pore water pressure of central part of the embankment foundation is smaller than that of both sides of the embankment foundation, and foundation treatment for eliminating liquefaction is not necessary for the central part of the dam foundation, and liquefaction degree can be effectively reduced by loading on both sides of the embankment foundation. The achievement can provide references for design of other similar projects.

Research on Geological Hazards and Prevention Engineering of a Power Plant Project Site

Zhu Qikun, Zhang Jinchao, Sheng Jianhao

2013, 27(6): 301-305. doi: 10.3969/j.issn.1007-2993.2013.06.008

[Abstract](49) [PDF 1937KB](6)

Abstract:
The construction project site is close to the north open-pit of a mine,the minimum distance less than 10 m to the open-pit boundary. In addition,a thickness of 1.5~3.0 m weak interlayer is distributed continuously in the site foundation,and exposed on the open-pit slope. The weak interlayer and the open-pit slop constitutes a bedding slope. Because of the special surrounding environment and the structure of foundation,the project maybe suffer geological disasters risks,such as site integral slipping and landslide,and the harmful consequences is very serious. According to the calculation results of the site integral stability and the open-pit slope stability,the weak interlayer safety factor can meet the technical code,and the open-pit slope is in instability and must be reinforced. Considering the site stratigraphic structure and surrounding environmentect,a comprehensive prevention scheme is proposed,including cutting slope and reducing load,pretesting frame anchor,drainage system and engineering monitoring. In accordance with the mechanical properties of rock and soil mass in anchorage section,the anchorage force is determined. The internal forces of the lattice beams are calculated by the models of Winkler foundation elastic beam and continuous beam. After cutting slope and anchoring,the slope stability checking express that the safety factor can satisfy the technical code.

Study on Subgrade Bearing Capacity of Round Gravel Stratum in Yanji——Hunchun Area

Gao Tao, Liu Fei, Zhou Jinghong

2013, 27(6): 306-309. doi: 10.3969/j.issn.1007-2993.2013.06.009

[Abstract](45) [PDF 665KB](7)

Abstract:
Round gravel stratum is the commonly used soil in engineering construction in Yanji—Hunchun area.In order to achieve reliable data about the characteristic value of subgrade bearing capacity of round gravel stratum,to approach appropriate measures for determining the characteristic value of subgrade bearing capacity,to test the degree of reliability of bearing capacity datum in former worke, in-situ testing methods including loading test and heavy dynamic penetration test (DPT) are taken for study the round gravel stratum and twelve sets of data which about characteristic value of subsoil bearing capacity and deformation modulus and about blow counts of DPT are collected. Through the statistical analysis of the test data, get the characteristic value of subgrade bearing capacity of the range of round gravel stratum. That the characteristic value of subgrade bearing capacity and blow counts of DPT linear related conclusion, so the deformation modulus and blow counts of DPT linear related conclusion. According to the conclusion, two experimental formulas adapting to the local engineering geological condition are proposed, one of which is for determining the characteristic value of subgrade bearing capacity of round gravel stratum by blow counts of DPT, the other is for determining deformation modulus by blow counts of DPT. The research is helpful to geotechnical engineering investigation work which can provide characteristic value of subgrade bearing capacity and deformation modulus of round gravel stratum reliably, accurately, conveniently, economically in Yanji—Hunchun area, and provide experience for other regions in Jinlin Province.

Before and After Earthquake Actions of Slope Stability Analysis with Limiting Equilibrium Method and Strength Reduction Method

Li Bo, Tang Aiping, Zhao Anping

2013, 27(6): 310-314. doi: 10.3969/j.issn.1007-2993.2013.06.010

[Abstract](32) [PDF 1969KB](5)

Abstract:
Respectively comparative study on limiting equilibrium method and ANSYS strength reduction method for the slope stability analysis under the earthquake action.Consider the role of the earthquake in the pseudo-static method applied vertical and horizontal directions of the earthquake force.According to before and after the earthquake action the two methods for slope stability coefficient, sliding surface and sliding body contrast analysis draw some conclusion.Two methods of safety factor and sliding surface that differs little, it is indicated that the strength reduction method applied to the slope stability analysis is reasonable.The strength reduction method that safety coefficient are slightly larger than the limit equilibrium method, this is due to the strength reduction method considering the relationship between the stress and the strain of soil, making the calculation results accord well with practice even more.Through the contrast of horizontal displacement diagram before and after the earthquake action can be found that regular,put forward the corresponding suggestions for earthquake zones of the slope anchor.

Analysis of Consolidation Effect of Vacuum Preloading Consolidation Without Conventional Top Sand Drainage Cushion on Newly Dreged Silt

Wu Xinglong, Zhang Kaiwei, Xu Jian

2013, 27(6): 315-319. doi: 10.3969/j.issn.1007-2993.2013.06.011

[Abstract](44) [PDF 1612KB](9)

Abstract:
The newly dredged silt has disadvantageous engineering properties of ultra-soft character and excess water content. It results in high requirements for post soft-ground treatment. For a future industry site filled with newly dredged silt, vacuum preloading consolidation method without drainage cushion was performed to improve the ground bearing capacity and reduce the post-construction settlement. Various approaches have been employed to investigate the ground bearing capacity after the treatment, including field testing, theoretical method and empirical methods from different design codes. The test results show vacuum preloading consolidation could increase the shearstrength of the newly dredged silt to a certain depth even without the conventional sand drainage cushion. The water content decreases substantially and the bearing capacity increases.Crust will be formed in short time on the surface of the newly dredged silt.

Application of CFG Pile to Local Ground Treatment of a Large Oil Tank

Yuan Yong, Su Peidong

2013, 27(6): 320-323. doi: 10.3969/j.issn.1007-2993.2013.06.012

[Abstract](33) [PDF 1609KB](6)

Abstract:
The paper introduces the handling methods of CFG pile in local ground treatment of large oil tank through engineering practice, which not only improve the strength of soft ground effectively, but also utmostly keep the coordination of different ground deformation. In view of the specialty of the tank shape, along the tank of the circle loop piles are adopted and the scheme of unequally spaced piles are adopted according to the vertical and horizontal differences of subsoil properties of different sections. The treatment effect of composite foundation is ideal and achieves the desired design goal. It provides a new design concept for the ground treatment of similar projects and could be a reference.

2013 Vol. 27, No. 6