岩土工程技术

Calculation Method of Pile Group Settlement Based on Single Pile Settlement

Zhang Qianqing, Zhang Zhongmiao

2009, 23(1): 1-4,22.

[Abstract](82) [PDF 337KB](6)

Abstract:
The selection of parameter of single pile settlement can be obtained more easily than the one of pile group. That means, if single pile settlement can be used to estimate pile group settlement, the problem will be easier. The settlement of single pile consists of compressive deformation of pile stem and settlement of pile tip. The compressive deformation of pile stem is calculated by adopting hypothesis of linear-elasticity and settlement of single pile tip is calculated by layerwise summation method. Furthermore, in the process of calculating pile group settlement, the method pays attention to the contribution made by compressive deformation of pile stem. Meanwhile, additional stress of pile tip is obtained by multiplying average stress under platform and coefficient of load transfer. According to similarities and differences of the method of calculating settlement between single pile and pile group, it shows a new way of calculation, which is single pile settlement estimates pile group settlement. This method can makes it easier choose parameter and do calculation. The last part of this paper introduces the application of the new way in calculating the pile foundation settlement of bridge project.

Graphic Method and Its Application in Curved Discontinuities

Yuan Guangxiang, Zhang Luqing, Yang Zhifa

2009, 23(1): 5-8.

[Abstract](39) [PDF 315KB](4)

Abstract:
It is very important to determine the relative ubiety and combination of discontinuities. Besides traditional projection on equatorial plane and numerical methods,a new method,coordinate projecting method,can be used in stability analyses of the blocks coordinate projection. It is important to simplify curved discontinuities as the collection of limited small planes when analyzing curved discontinuities. The Qingfeng cavities in Shepandao is given as an example to analyse curved discontinuities with coordinate projection.

Deformation Monitoring and Analysis of Building Near Foundation of Tunnel in Construction

Xiang Ruide, Yao Aijun

2009, 23(1): 9-13.

[Abstract](37) [PDF 341KB](5)

Abstract:
The around environment of tunnel deep foundation pit in Beijing is complexity, and the foundation pit is transmeridional, the lenth is 173. 6 meters. North of the foundation pit is Zhichun load, and the south is a series of structure. The distance of the building and the foundation pit is only 2. 06 meters, furthermore the building was used many years. Based on spot checking and detection, the foundation of the building generated obvious asymmetrical settlement in construction of tunnel foundation, therefore, acclivitous split appeared in jamb wall of superstructure. So, it's need to monitor deformation and settlement of the building uninterrupted, analyse and deal with monitor data in time, and submit the result to construction organization. Then, construction organization can adjust construction scheme to proceed informational construction, and ensure safety of the building. The result has instruction function to similar subway project in Beijing area.

Stability Study of Expansive Soil Slope Based on Discontinuous Deformation Analysis

An Yanyong, Lin Yuliang, Xu Yanhua

2009, 23(1): 14-18.

[Abstract](37) [PDF 359KB](4)

Abstract:
Discontinuous deformation analysis (DDA) method is a newly developed numerical method and has gotten widespread attention and approval of many scholars in geotechnical engineering because of its advanced principle and numerical simulation technique. Geological model and mathematical model were established based on the damage characteristics of expansive soil cutting slope of Ningming highway. 2D model was established and theory system of the discontinuous deformation analysis method was developed. Constitutive theory of unsaturated soil was used and control constants were discussed. Then, DDA procedures were used to simulate the damage characteristics of the expansive soil slope. The results matched with the actual situation, and thus shows the procedures is rationality and effectiveness, Its results can he used for design and construction.

Discussion on Lining Structure Calculation Method of Multi-arch Tunnel With Compound Mid-board

Wang Tao, Fang Zhongqiang, Li Hao

2009, 23(1): 19-22.

[Abstract](63) [PDF 309KB](5)

Abstract:
As the theory of calculation method of designing load is immature, and the existing calculation model could not calculate the lining structure of multi-arch tunnel exactly, so there is not a united method to calculate the lining structure. Based on the two slumping arches assumption, a load defining method of multi-arch tunnel is put forward. The interaction between mid-board and lining structure is simulated by pressure springs, and the lining structure calculation model of multi-arch tunnel with compound mid-board is established based on load-structure method. Combing the design and calculation of Fenghuang tunnel in Suzhou, the lining structure is calculated by the model, and the reinforcement ration and stress safety factor are calculated, and this could provide useful discussion on the design and calculation of multi-arch tunnel with compound mid-board.

Evaluation on Dyke Safety Affected by Trenchless Pipeline Engineering

Li Zhijun

2009, 23(1): 23-25,38.

[Abstract](41) [PDF 322KB](4)

Abstract:
Trenchless pipeline engineering will form an excavation disturbed zone around piping, and the zone will lead to groundwater flow variation and affect dyke safety. According to an actual engineering example, taking account of such unfavorable factors as highest flood stage and river channel erosion, a groundwater numerical simulation model is built for simulating the maximum groundwater hydraulic gradient. Based on the critical hydraulic gradient method and the safety coefficient recommended by relevant criterion, the quantitative analysis on the possibility of pipeline engineering induce infiltration destruction is study.

Discussion on Significances of Natural Moisture Content and Limit Moisture Contents of Soft Clays

Guo Jinjing, Wang Fang, Zhao Guangpeng

2009, 23(1): 26-29.

[Abstract](42) [PDF 384KB](8)

Abstract:
Based on the analysis for the differences between the theoretical definitions of w,w_P and w_L of soft clays and usually used their test values, in consideration of different water forms and their functions in soft clay, it is suggested that w should be redefined as the ratio of total water mass except for strong combined water and soil grain mass, where soft grain means the integrated particles of real soil grains and strong combined water. This definition can avoid the confusion between theoretical definition and test results. The limit moisture contents (w_L,w_p) and deduced plastic and liquid indexes(I_L, I_p) from limit moisture contents (w_L, w_P) are all obtained from remold soft soil test without considering the effect of the natural structure of soft soils for them. Therefore, it is proposed that introducing a structure coefficient which can get from structural study for soft soil, emends the w_L, we, I_L and I_p. Emended w_L, w_P, I_L and I_P will be conformed to natural soft soil engineering practice. Meanwhile, on the interaction between clayey particles and different form water in soft soils and different function of different form water for the soft soil deformation mechanism, implication of w_L. and w_p should be revised, that is, wp represents minimum weak combined water contents and w_L represents maximum weak combined water contents with little free water.

A Method to Determine Subgrade Bearing Capacity

Li Shunqun, Wang Yinghong, Liu Shuangju

2009, 23(1): 30-33,47.

[Abstract](42) [PDF 356KB](6)

Abstract:
No linear qualities of triaxiat tests results and direct shear tests results encourage a proper curve to be constructed to illustrate soils' limit equilibrium state based on Mohr envelope. With the application of elastic theory, equations are derived to calculate plastic range of ground under band-load operation, and then, critical load and plastic zone can be obtained. Several conclusions on the shape and size of plastic zone induced by band-load can be got after the comparison, which is performed between results respectively from the two methods. Even the difference between the shape and the size of the two kinds of plastic zone created by the same load is small and the two critical loads have the similar character, plastic zone increment with increasing upper load is quicker when the proposed method is applied.

Study on Effect of Dynamic Consolidation to Grain-size Composition and Collapsibility of Loess

Nan Yalin, Liu Haisong

2009, 23(1): 34-38.

[Abstract](38) [PDF 445KB](7)

Abstract:
Based on the electron microscope scanning and the test of grain-size with high precision, the changes of grainsize composition before and after the treatment of dynamic consolidation are discussed with the subgrade loess of Xi'an-Yumenkou express way,and its effect on loess collapsibility is also analyzed. It could be concluded that dynamic consolidation could destroy the original grain-framework of loess, the surface cementation of conglomeration peeled, grain become thinner and filled in pores which made pores significantly reduced; soil structure become compacted and loess-collapsibility become weaker or even disappear. This study reveals the mechanism of loess-collapsibility treated with dynamic consolidation.

Freezing Damage Prevention Technics of Retaining Wall in Seasonal Frozen Soil Region

Nei Wenjie, Yuan Anli

2009, 23(1): 39-43.

[Abstract](69) [PDF 387KB](6)

Abstract:
Based on the studies of the frozen soil mechanics and the frozen soil physics in the recent years,the main content of the prevention technics of the retaining wall in the seasonal frozen region are briefly introduced. They may be references for the engineers because the contents widely include freezing damage forms, the reasons of the freezing damage, calculation methods of the prevention structures and the design parameters determination of resisting the frost heaving of the retaining wall.

Test and Analysis for Surrounding Rockmass Disturbed Zone of Underground Cavern

Dong Yanjun, Huang Zhipeng, Chen Saichao

2009, 23(1): 44-47.

[Abstract](32) [PDF 366KB](6)

Abstract:
The excavation of the underground chamber causes the redistribution of the geostress, and certain thickness of the disturbed zone produced surrounding rockmass. It is important to measure out the thickness of the disturbed zone for evaluating the stability of the surrounding rockmass and designing the support of tunnel. Comparing the results of supersonic test with the results of monitoring the displacement during the construction, the scope of the tunnel wall rocks disturbed zone can be measured,and the fit parameters is offered for support of the wall rocks.

Graded Granular Flexible Base of High-grade Highway

Li Limin, Yang Jianmin

2009, 23(1): 48-51.

[Abstract](27) [PDF 284KB](4)

Abstract:
Through test road, paving test road, two types of highway structure and gradation of the graded granular-flexible base are put forward, and the construction technology of the graded granular-flexible base is studied systematically, in the paper,which can be taken as a reference for design and construction of the graded granular flexible base.

Rock-burst and Its Countermeasure of TBM Construction in Drainage Tunnel of a Hydropower station

Luo Zhihu, Yang Pengfei

2009, 23(1): 52-55.

[Abstract](75) [PDF 405KB](11)

Abstract:
It had only been tunneled 1 027 m in previous 101 d in construction drainage tunnel of the Jinping Second cascade hydropower state. It had occurred 3 times rock-burst altogether in this period which immediately influence the tunneling process. The harm degree and the influence area of these rock-burst according to the time sequence which rock-burst occurred are discribed. The occurrence of rock-burst has certain regularity, which is not only related to high in-situ stress,but also related to the structural features of rock mass and the water conditions,etc. Simultaneity, the construction characteristic of TBM is also one of the factors which intensifying the occurrence of rock-burst. Utimately,it proposes the corresponding countermeasures by analysis for the occurrence regularity of rock-burst.

2009 Vol. 23, No. 1