岩土工程技术

Unified Formula for Settlement Calculation Considering Buried Depths of Foundations

Hu Pengfei, Zhang Zaiming, Yang Yuyou

2008, 22(4): 163-168.

[Abstract](37) [PDF 2879KB](11)

Abstract:
By comparing and analyzing the distributions of Mindlin stress coefficient and Boussinesq stress coefficient under the corner of rectangular uniformly-distributed load with different buried depths and length-width ratio, the relationship between Boussinesq and Mindlin solutions is established statistically. The experiential coefficient for settlement calculation is obtained by back analysis on the measured settlement results of about sixties buildings in Beijing. An unified formula for settlement calculation characterized by a coefficient of correction for depth is proposed finally. The formula is suitable for the settlement calculation of both natural foundations and pile foundations.

Analysis of Interaction Between Pile and Soil

Zhang Qianqing

2008, 22(4): 169-172,193.

[Abstract](42) [PDF 419KB](8)

Abstract:
When soil deformation between the cap and the pile toe is equal to the penetration of pile toe and the compressive deformation of pile stem, pile-soil interaction occurs. Based on this postulate, a new simplified analytical method for pile-soil interaction is proposed. According to this method, the loading which is shared by the soil between the cap and the piles can be determined at an arbitrary loading, and the quantity of piles can be conveniently determined. Meanwhile, the foundation settlement is produced by the soil deformation between the cap and the pile toe and by the compression of soil under the pile toe, and the foundation settlement can be well calculated relatively. At last, the design load of single pile can be determined by the allowed settlement of building. An example shows that the proposed method is satisfactory.

Approximate Solution to Safety Factor of Slope Stability Under Plane Strain Condition

Yang Xueqiang, Ling Pingping, Chen Guilin

2008, 22(4): 173-177.

[Abstract](37) [PDF 801KB](8)

Abstract:
Mohr-Coulomb yield criterion, which does not consider the contribution of intermediate principal stress to soil strength,is a conservative yield criterion, thus Drucker-Prager yield criteria transformed from the Mohr-Coulomb yield criterion under approximate plane strain condition, will give conservative estimation of safety factor for plane strain slope stability analyses. Relatively, Matsuoka-Nakai and Lade-Duncan yield criteria both consider the influence of the intermediate principal stress on soil strength effectively, thus Drucker-Prager yield criteria transformde from the Matsuoka-Nakai and Lade-Duncan yield criteria under approximate plane strain conditions, could give a reasonable failure strength predictions for geo-materials, soil shear strength could be exerted more sufficiently under plane strain status, and therefore more reasonable and real safety factors could be exerted more sufficiently under plane strain status, and therefore more reasonable and real safety factors could be obtained by using the transformed Drucker-Prager yield criteria for slope stability analyses. Calculation results of planme strain slope stability given by using ANSYS prove above views.

Application of Fuzzy Mathematics on Rock-slop Stability Analysis

Meng Heng

2008, 22(4): 178-181.

[Abstract](44) [PDF 181KB](9)

Abstract:
The key of the evaluation method, as a method of slope stability evaluation, lies in the accuracy of the established judgment model, and the determination of the membership and the weights of the evaluation factors are important to the judgment model. In practice, the expert scoring method is widely used in weights determination, though the method is subjective. Judgment Matrix Analytical Method is used to determine the weights of the evaluation factors and Secondary Fuzzy Evaluation is used in the calculation and analysis of a real project. This method shows to be convenient and closing to the reality.

Fuzzy Isoline of Site Classification Based on Known Datum of Drill Holes

Liang Shijun

2008, 22(4): 182-185.

[Abstract](33) [PDF 2099KB](6)

Abstract:
The fuzzy mathematics theory with accordance to the method of site types partition of "Code for seismic design of buildings" (GB 50011-2001)is applied to deduce the fuzzy quadratic appraisement method of site types, fuzzy vector and fuzzy characteristic period of site types is put forward, which achieves continuum of site types partition. Based on the collected datum of site types, the geo-model is constructed, which makes fuzzy isolines of site types and characteristic period available. In comparison with real datum measured, the site types by this fuzzy isoline is consistent with site types defined by "Code for seismic design of buildings", and fuzzy characteristic period are consistent with the period from the code very well, which justifies the significance of fuzzy isoline to seismic construction design.

Analysis of Pile Foundation Behavior Due to Excavation by Two-stage Method

Yu Feng

2008, 22(4): 186-189,197.

[Abstract](37) [PDF 879KB](5)

Abstract:
Based on Winkler's foundation model and compatibility condition of pile and surrounding soil, Two-stage Method is used for setting up horizontal displacement governing equation of a single pile. Pile-pile interactions and those between pile and surrounding soil can be achieved according to simplified Mindlin's equation. Then, governing equations for pile groups are obtained by combining points above. Comparisons are drawn between the observed results of centrifuge model tests and those computed by the studied method.

Settlement Calculation Method of Dry Jet Mixing Pile Composite Foundation

Hu Xuemei

2008, 22(4): 190-193.

[Abstract](27) [PDF 365KB](7)

Abstract:
Based on the previous research of the settlement calculation to Dry Jet Mixing (DJM) pile composite foundation and the regularity of load transfer, a practical settlement calculation method of DJM pile composite foundation is put forward.

Forecast on Hydrologic Condition Leaded to Overflow Burst of Baishi Landslide Dyke

Jiang Zhongxin

2008, 22(4): 194-197.

[Abstract](33) [PDF 1231KB](6)

Abstract:
The hydrologic leaded to overflow burst of the Baisha landslide dyke is predicted in order to prevent the burst flood and debris flow. Based on characteristics discussion of the landslide and landslide dyke, the burst type, critical bead of burst with overflow type and flow rate leaded to burst are forecasted. The forecast shows that only the floodwater encountered in 100 years may cause dam break.

Deformation and Displacement Features and Forming Mechanism of Tiantai Landslide in Xuanhan Sichuan

Xiong Daokun

2008, 22(4): 198-202.

[Abstract](33) [PDF 3464KB](8)

Abstract:
The Tiantai Landslide is a soil one of extra large-scale occurred in the region of gentle slope and gently dipping formation. The main character is slipping in multi-stage and mass-by-mass. It's horizontal displacement is the largist in the front and reducing towards the back. Five secondary deforming patterns are summarized according to the varied platform topography with troughs and ridges, the essential conditions producing the multi-stage and mass-by-mass sliding is analyzed, and genetic model forming the mass-by-mass sliding by water pressure is established.

Eccentrically Loaded Strip Foundation on Geogrid-reinforced Sand

Li Yuzhou, Nie Xiaoqing

2008, 22(4): 203-207.

[Abstract](32) [PDF 1938KB](5)

Abstract:
Results are presented for laboratory model tests conducted to determine the ultimate bearing capacity of an eccentrically loaded strip foundation supported by geogrid-reinforced sand. Only one type of sand at one relative density of compaction and one type of geogrid were used for the tests. The depth of the foundation was varied from zero to B (width of foundation). Based on the laboratory test results, an empirical relationship called reduction factor has been suggested that correlates the ratio of the ultimate bearing capacity of an eccentrically loaded foundation with that for a foundation where the load is applied centrally.

Review on Pile Quality Accident

Zhu Kui, Xu Riqing, Zhou Pengfei

2008, 22(4): 208-212.

[Abstract](40) [PDF 461KB](9)

Abstract:
The reasons of pile quality accident are analyzed from investigation, design and construction, and pile quality accidents are classified through engineering examples. It is hold that unsound investigation, design fault and unstandardized construction are the main reasons for pile quality accident.

Engineering Behavior and Ground Treatment Methods in Glacial Till Layers

Xie Chunqing, Qiu Yanjun, Wang Wei

2008, 22(4): 213-217.

[Abstract](33) [PDF 1569KB](7)

Abstract:
Based on engineering practice in one national key project, a comprehensive study on the engineering behavior of glacial till layer using various testing methods including filed investigation, survey, laboratory gradation analysis, compression test, shear test, chemical analyses test, standard penetration test, dynamic penetration, volumetric analysis, load test, wave velocity test, and well pumping test is reported. Ground treated with dynamic compaction and rolling compaction is observed with respect to the deformation of original ground and high fill embankment. Research results show that glacial till as natural ground and/or fill material can be used in the construction of airport, highways and building.

2008 Vol. 22, No. 4