岩土工程技术

Suggestions on Checking Computation of Underlying Stratum With Soft Soil in Pile Foundation

Li Guangxin, Zhang Zaiming

2007, 21(3): 109-112.

[Abstract](44) [PDF 309KB](10)

Abstract:
The different methods of checking computation of underlying weak layer in pile foundation which are suggested in different codes or handbooks are analyzed. Some suggestions are proposed:the self-weight stress of soil which is between the base of cap and ground surface are added in or subtracted from separately in different stress calculations, the shaft friction around the pile group which is deducted in computation of additional stress is the characteristic value rather than limit value, and the checking computation is carried out from ground surface of basement in the case of strip footing and individual footing in basement.

Inclined Value Estimation of Thick Raft Rigid Foundation

Li Lianying, Wang Hua, Liu Kun

2007, 21(3): 113-115.

[Abstract](44) [PDF 287KB](7)

Abstract:
Based on the Boussiuesq solution of elastic half space, the inclined value calculating method of thick raft foundation is inquired by using finite element method and compression level ground model to estimate the differential settlement and the inclined value of thick raft foundation. And the project example is given. Results of calculation are in accordance with that of the actual measurement.

Machanical Analysis on Pipe Roof Advaned Support in Shallow Excavation

Wu Jianwei, Song Weidong

2007, 21(3): 116-121.

[Abstract](31) [PDF 334KB](6)

Abstract:
Pipe roof method, one of the advanced support patterns in underground engineering, is often used in the construction of shallow excavation. During the period of construction, the responses and deformation of the pipe umbrella are complex, so the theoretical analysis and calculation of the pipe umbrella is necessary. Based on the loading-structure mode, which regards the pipe as an Winkler elastic foundation beam and the covering soil as the load, combined with the usual excavation way in the underground engineering under the pre-support of the pipe umbrellas, an overall analysis on every excavation step is given, and calculation equations of pipe responses for the whole pipe is put forward. Then, with the example of a certain shallow buried underpass, the analytic method and FDM numerical simulation is adopted respectively. Finally, the comparation of the results and practical experiences proves that the analytic method presented is reasonable and can be referred for the pipe proofing design and construction.

Approach of Liquid Limit and Plastic Limit Test for Mixed Soil

Liu Fuchen, Sun Yuzhuo, Wang Qitian

2007, 21(3): 122-122,133.

[Abstract](47) [PDF 107KB](9)

Abstract:
The liquid limit and plastic limit test is a conventional geotechnical experiment. The mixed soil contains quantity of coarse grain. The liquid plastic limit value of the test with particle size of 0.5 mm below is debased, and the soil classification does not conform to the fact. The liquid plastic limit test with particle size of 0.075 mm below is suggested.

Relations Between Seepage Force and Water Pressure Around Slice in Slice Method

Shi Weimin, Fu Yuhui

2007, 21(3): 123-125,152.

[Abstract](25) [PDF 340KB](7)

Abstract:
The seepage force and the water pressure force is considered simultanously in the slope stability analysis every so often at present, which causes the water pressure force is double calculated. Based on the example of Sweden slice method, defined the water pressure around the slice utilizing the flow nets property. It is proved that the seepage force is equilibrant to the water weight and the water pressure around the slice, clarified the mistiness knowledge, and corrected the calculation methods.

Application Case of Low-grade Plain Concrete Pile Foundation in Covered Karst Region

Wang Xianneng, Zhang Zhentao

2007, 21(3): 126-130.

[Abstract](62) [PDF 448KB](9)

Abstract:
Pile foundation is widely used in the complicate geological condition in covered karst region, and composite foundation can be adopted when the overburden thickness is enough. Recent years witnessed the increasing use of rigid pile foundation to reinfore the vital structure that the settlement is controlled strictly. The karst geological condition, the design and construction, and the settlement observation result of the low-grade plain concrete pile composite foundation for the Longgang Culture Center in Shenzhen is expounded in details. It shows that this composite foundation technology is ad-visable in karst region, and can be a feasible treatment for similar engineering.

Mechanical Properties of Interface Between Soil and Steel

Zhang Xiaofeng, Yuan Juyun

2007, 21(3): 131-133.

[Abstract](34) [PDF 344KB](7)

Abstract:
Based on the direct shear test on the interface between soil and steel, deformation characteristic of the interface is studied, and the influence of normal stress on the shearing failure deformation is analyzed. The analysis result indicutes that the relationship between shear stress and shear displacement is hyperbolic, and the shear stress is influenced by normal stress.

Classification for Unsaturated Soils by Overlapping State of Pore Water

Li Shunqun, Cui Chunyi, Zheng Gang

2007, 21(3): 134-138.

[Abstract](28) [PDF 396KB](7)

Abstract:
Based on thermodynamics theory and foundational principle of soil mechanics, geometrical relation between ball-shaped particles and pore water is employed to investigate the force system in unsaturated soils induced by unsaturation. And then definitions for tension suction and suction ratio are construted. Another concept named equivalent suction is put forward after magnitude of suction as well as correspondiog effective area of matric suction and tension suction on particle surface are taken into consideration. Study on an ideal model shows unsaturated soils can be rationally divided into overlapping unsaturated soils and non-overlapping unsaturated soils according to whether meniscus overlaps on particle surface or not. Tension suction only appears in overlapping unsaturated soils and contributes to strength but not to seepage is another achieved conclusion.

Multistage Grouting Model in Slope Reinforcement

Liu Xianmu

2007, 21(3): 139-143.

[Abstract](24) [PDF 486KB](5)

Abstract:
The feasibility of slope reinforced by grouting is proved and multistage grouting(PG) is put forwatd. Based on the traditional theory of fill grouting, penetration grouting, compaction grouting and hydrofracture grouting, the formula of grouting press,grouting radius and grouting stress of multistage grouting in different phase and stratum is deduced by the introduction of the elastic and plastic theory about glob and column expansion,Boussineq's and Terzagh's theory. The calculation model for multistage grouting design and statistical rule of concrte-clay from a lot of experiment and test data is summarized. The multistage grouting model is testified by the engineering practice.

Vibration Produced by Heavy Tamping and Its Environmental Effect

Shi Youzhi

2007, 21(3): 144-148.

[Abstract](48) [PDF 223KB](11)

Abstract:
Dynamic compaction is one of the methods for ground treatment. But the vibration during dynamic compaction often becomes a problem that restricts the application of dynamic compaction. Base on the study results at home and abroad,the vibration produced by heavy tamping and the environmental effect is selectively analyzed. Combined with dynamic compaction vibration of a coastal engineering, the vibration produced by heavy tamping is analyzed too. The safe distance of heavy tamping construction is determined.

Overstretch Unloading Method of Pre-stressed Anchor Ropes

Wang Qirui, Tang Jun

2007, 21(3): 149-152.

[Abstract](38) [PDF 417KB](7)

Abstract:
Combining practical engineering example, the method of unloading the anchor ropes pre-stress through overstretch is reviewed, and the influence of anchor ropes working effected by the loading-unloading-reloading function process is analyzed.Based on contrasting the results of pretighten and stretch, and monitoring the work of anchor ropes, the feasibility of the overstretch unloading method is illustrated.

Informational Construction of Deep Foundation Pit Supporting

Lv Wentian

2007, 21(3): 153-155.

[Abstract](26) [PDF 344KB](6)

Abstract:
This paper demonstrates informational construction technology. During the process of constructing, the combination of data and the circumstances of the excavation engineering is synthetically analyzed, experimental data are made used of to produce feedback design and analysis, and these are of practical and theoretical sinnificance in the following work. The monitor during the working process of some deep excavation construction is introduced, and the importance of information construction is indicated. According to analysis on the data, information conclusion, and experience summary during information construction, there is a reference to similar projects.

Application of Super-long DX Pile in Soft Soil Foundation of a High-rise Building

Bao Shengmou

2007, 21(3): 156-159.

[Abstract](45) [PDF 336KB](7)

Abstract:
DX pile is a new kind of variable section pile based on the bored filling pile. The partial enlargement of the pile boby, such as carrying plate and carrying branch, grcatly improve the bearing capacity of the pile and make full use of the bearing capacity of the surrounding soil. DX multi-nodal enlarging-grouting pile and the result of its application in soft foundation of a high-rise building in Zhejiang province is introduced.

Experimental Investigation of the Bearing Capacity of Piles in Unfrozen Soil and High-Temperature Permafrost

Lv Xiaoliang, Zhou Guoqing, Bie Xiaoyong

2007, 21(3): 160-163.

[Abstract](32) [PDF 402KB](5)

Abstract:
Taking the bridge pile foundation of Qingshui River as a prototype, the stability of piles in unfrozen soil and high- temperature permafrost is investigated by the indoor simulation test. Based on the study of the bearing capacity of the pile foundation in unfrozen soil and high-temperature permafrost, it is found that the bearing capacity of the latter is 11.6 times that of the former. The experimental investigation provides reference to the construction of preventive measures for Qinghai-Tibet railway project.

2007 Vol. 21, No. 3