岩土工程技术

Characteristis Values of Tip Resistance on the Rock for the Weak Underlying Stratum

Luo Zhaohua

2011, 25(6): 271-277. doi: 10.3969/j.issn.1007-2993.2011.06.001

[Abstract](51) [PDF 468KB](9)

Abstract:
From the point of punching damage mode of rock tensile strength, a mathematic model of punching safety indices and punching tip resistance value coefficient was established based on the analysis of rock characteristics and rock mechanical strength. Stretch and compression strength, punching safety indices and tip resistance coefficient of sedimentary rock were calculated by use of the empirical data of mechanical property of rock, and their characteristics were analyzed respectively.It is concluded that it tends to be unsafe that the relative standard provides 3d thickness of hard rock which has high compression strength and low stretch strength overlying weak subsoil bearing strata based on the use of uniaxial saturated compress strength as tip resistance value. The punching tip resistance coefficient of rock with different lithology, integrity and safety classes was calculated by tip resistance mathematic model and rock mechanical empirical data.The proposed value of tip resistance coefficient of the rock overlying weak bearing strata is given after comparing the calculation outcomes with resisting compression tip resistance values from references.

Experimental Study of Water Content Influence on Shear Strength of Unsaturated Soil

Wang Xingxing, Hou Kepeng, Ma Kaichuan

2011, 25(6): 278-280,285. doi: 10.3969/j.issn.1007-2993.2011.06.002

[Abstract](99) [PDF 713KB](9)

Abstract:
The research on shear strength of unsaturated soil is important in soil mechanics research. The shear strength of soil depends on the difference of water content. Based on the object of remolded soil in Yunnan province and the means of the direct-shear tests, the author surveyed the shear strength parameter of soil with different water content.According to the test results, the shear strength of soil don't decreased monotonously with the increasing of water content, interest of a parabola with up and down,which is some positive significance to know the relationship of between soil strength and water content.

Monitoring and Analysis of Deep Excavation of Subway in Complicated Environment

Yang Huawei, Li Liang

2011, 25(6): 281-285. doi: 10.3969/j.issn.1007-2993.2011.06.003

[Abstract](37) [PDF 931KB](8)

Abstract:
Because of the complexity of ambience, in the construction of city subway, foundation pit excavation can cause disturbance to the soil, and bring damage to the building and underground pipe, even the stability of foundation pit can be lost. Based on the project of Shenzhen metro,introduced the design and construction of the deep foundation pit,discussed the monitoring scheme of foundation pit excavation, also analyzed and summarized the monitoring result. Project example shows that choosing reasonable monitoring scheme and carrying out real-time dynamic control to environment and retaining structure ensured the safety of the excavation process.

Tunnel Construction Water Inflow Predicted by Precipitation Infiltration Method

Huang Zhonghuan, Wang Ling

2011, 25(6): 286-288. doi: 10.3969/j.issn.1007-2993.2011.06.004

[Abstract](55) [PDF 195KB](4)

Abstract:
Water inflow is generally obtained form well pumping test.But in geological survey and route selection,the precipitation infiltration method is used in the prediction the wate inflow of the construction of the tunnel because of the site condition and the cost constraints.

Characteristics and Monitoring Methods of Ground Subsidence in the Gob Area of Beijing West Mountain Areas

Huang Laiyuan

2011, 25(6): 289-294. doi: 10.3969/j.issn.1007-2993.2011.06.005

[Abstract](53) [PDF 1049KB](10)

Abstract:
The gob area of Beijing are mainly located in the Beijing west mountain areas, resulting in ground subsidence, surface deformation,causing further damage to the ground buildings, roads, railways, pipelines and other linear projects distorted,damaged farmland, forest damage, and even casualties, etc. In recent years, with national and local government industrial policy of gradual adjustment, Beijing gradually shut down all small coal mine, and most of the towns, but the historical legacy of underground mined is still threatening people's lives and property, this paper describes several technical methods for disaster monitoring at home and abroad,attempts to explore technical methods to monitor mining collapse, which is suitable for the Beijing west mountain areas,this will provide a reference for the capital disaster prevention and mitigation.

Softsoil Subgrade Settlement Curve Fitting by L-G Superposition Curve Model

Zhao Fengqi, Zhang Xiong, Wang Weisheng

2011, 25(6): 295-299. doi: 10.3969/j.issn.1007-2993.2011.06.006

[Abstract](67) [PDF 301KB](4)

Abstract:
To improve the fitting accuracy of Soft soil-Settlement model,by the analysis of measured data,studied the soft soil subgrade settlement development rule.The Logistic forecasting model and Gompertz forecasting model were superimposed on the basis of predecessor's research,and the L-G superposition curve model was set up in subgrade settlement,gave the approach of resolving the optimization model.By engineering project analyzed its fitting efficiency.By comparing the results of field observation data with calculation,not only the fitting accuracy of the new model is better than that of the Logistic model and Gompertz model,but the dependability of the combinational model is superior to each single model.The new model of L-G was scientific and applicative.It provides an effective analysis method for the inspected data of the settlement of foundation.

Analysis on Deformation of Retaining Structures of Over-excavation in Foundation Pit

Xie Xiudong, Wang Yan

2011, 25(6): 300-303. doi: 10.3969/j.issn.1007-2993.2011.06.007

[Abstract](48) [PDF 495KB](6)

Abstract:
During the excavation of foundation pit in rheological soil layer,the phenomena of over-excavation and support setting not timely occur frequently,and the characteristics of soft-soil creep,the deformation of retaining structures is increase sharply. With the secondary development program of the elastic-viscose-plastic constructive model,simulate the conditions of normal construction and over-excavation of foundation pit in Soft clay area,analyze the time change regulation of retaining structures and safety state of foundation pit,in order to achieve effective control of the deformation and protect the buildings adjacent to foundation pit.

Analysis of the Impact of Distance From Explosive Source on Blasting Vibration Signal Spectrum

Bi Weiguo, Tian Gang, Yan Yongfeng

2011, 25(6): 304-306. doi: 10.3969/j.issn.1007-2993.2011.06.008

[Abstract](51) [PDF 203KB](4)

Abstract:
Combined with a Tunnel Engineering in Linyi City,the spectrum changing situation of vibration signal at different distances from explosive source was analyzed through the analysis software MATLAB. It can be obtained that,in the medium and near-field of blasting source,the vertical component of the dominant frequency of vibration signal is larger than that in horizontal direction and the main vibration direction of ground vibration's peak velocity may change from horizontal direction to vertical direction with the increase of the distance from explosive source,and the overall trend decreases with vibration dominant frequency tending to low frequency. In engineering blasting site similar to this engineering in blasting parameters and features of the blasting region,the energy proportion of the horizontal component of vibration signal with low frequency is higher than that of the vertical component,and the impact of blasting vibration on building structures also can not be neglected even at the position far from the blasting source;in particular,seismic fortification in horizontal direction should be enhanced.

Numerical Simulation of High Filled Embankment on Slope Soft Foundation

Liu Xiujun

2011, 25(6): 307-311. doi: 10.3969/j.issn.1007-2993.2011.06.009

[Abstract](51) [PDF 946KB](3)

Abstract:
This paper building a high filled embankment FLAC^3D model by GOCAD, which embankment is on slope soft-soil foundation of Chen-Ning highway in Hunan Province. The FLAC^3D program was been adopted to simulating and analyses the embankment's deformation and stability under its own weight when layered filling. The following conclusions:The displacement of embankment is significantly affected by the landscapes;With the increase of embankment height,the settlement of embankment increases,and the position of largest settlement is about at one-third of filling height in the interior of this embankment;With the increase of embankment height,the lateral displacement of embankment presented to deformation on both side.

Displacement Monitoring Methods in Geotechnical Engineering and Accuracy Analysis

Qin Yue, Wu Jie

2011, 25(6): 312-315. doi: 10.3969/j.issn.1007-2993.2011.06.010

[Abstract](28) [PDF 237KB](4)

Abstract:
In the geotechnical engineering displacement monitoring, the choice of methods in monitoring depends on the condition monitoring. This paper used in the small Angle measurement method, angular intersection method, distance intersecting method, Total synthesis methods are studied. At present various documents, usually the coordinates calculation method are only gives. At best mean square error and mean square error of points in the direction of the coordinate. But mean square error in other direction is imponderable. Based on the above all sorts of monitoring method is deduced error ellipse, which can calculate the mean square error of monitoring points along each direction and estimate accuracy.

Design and Construction of Burity Ultimo Pits in Luanda

Zhang Wu, Liu Shaowen, Bian Wenfei

2011, 25(6): 316-320. doi: 10.3969/j.issn.1007-2993.2011.06.011

[Abstract](31) [PDF 946KB](5)

Abstract:
It's described that the design concept and construction process of a building pit which sites in Luanda,the capital of Angolan. The example shows that structure surface area and building site area ratio 92.5% by the combination of nail and anchor supporting structure. Utilizing the feature of the pit side soil appropriately, the pit excavation depth is more than 14m with vertical slop, and has little no dangerous on normal function and structural safety of dwelling houses which is from the pit at the edge of 0.3~0.5m.The maximum horizontal displacement of the pit can be observed is less than 3mm, The supporting structure endured repeated heavy rains, and its safe periods are past 2 years.

The Application of the Steel Pipe Braces & High-pressure Jet in the Processing Hole Excavated for Building Foundation Dangerous Situation

Dong Junzhao

2011, 25(6): 321-324. doi: 10.3969/j.issn.1007-2993.2011.06.012

[Abstract](30) [PDF 659KB](12)

Abstract:
Some underground garage deep hole excavated for building foundation project in Suzhou, ground situation for Suzhou typical soil layer, the biggest cutting depth is 5.25m with the drill hole filling pile supports and protections watering soil to stop the water curtain to carry on the supports and protections.This project is planed originally to completes the hole excavated for building foundation part before March, 2011, but in order to snatch the progress, construction and so on only then carries on the underground garage the peripheral high-level housing construction to 10 strata times excavating.In July, 2011 when excavates the underground garage hole excavated for building foundation, in the guard stake wall flank appears the horizontal direction crack, also the development is rapid, third days on the development are 10cm, latter decided to use the steel pipe braces & high-pressure jet to carry, after process processing, the dangerous situation was under the control, has avoided a bigger loss.

2011 Vol. 25, No. 6