岩土工程技术

Aapplication and Research for Determining Coefficient of Consolidation of Soft Clay

WANG Yuxia, XU Botao

2010, 24(5): 217-220,226. doi: 10.3969/j.issn.1007-2993.2010.05.001

[Abstract](30) [PDF 297KB](10)

Abstract:
In the calculation of consolidation degree of sand drain ground, coefficient of consolidation is an important parameter. Normally we get the coefficient of consolidation by laboratory testing, but it is diffieult to prepare solid specimen for radial coefficient of consolidation. In the paper, the writer uses pore water pressure time curve on soft base treatment to calculate reckoning the consolidation degree of soft clay, analyzes by comparing with the laboratory test result, it summarizes their mutual relations and changes regularity. The result can be referenced for similar design.

Improvement Analytical Method for Retaining Structures of Deep Foundation Pit Based on Planar Frame Model

WU Song, WU Dazhong, WANG Nengjun

2010, 24(5): 221-226. doi: 10.3969/j.issn.1007-2993.2010.05.002

[Abstract](20) [PDF 420KB](4)

Abstract:
Because of the model error and the error of soil mechanics parameters, traditional planar frame model cannot exactly reflect the general situation of displacement of the pit. In order to improve the accuracy of the calculation, an improvement method is proposed by modifying the computational mechanics parameters of the soil. They were determined by taking the positive back analysis process. A radial basis function neural network and the compatible space computing model was introduced to take the back-calculation process, It is proven that the result is more accurate than the result of the traditional method.

Research of Characteristics of Roof Strata Movement in Underground Coal Gasification Process

ZHENG Huihui, ZHANG Xinghua, LIU Xiliang

2010, 24(5): 227-230. doi: 10.3969/j.issn.1007-2993.2010.05.003

[Abstract](35) [PDF 229KB](3)

Abstract:
The thermal elastic plastic model and finite element software were used to simulation the whole process of underground coal gasification, and obtained displacement of different positions of roof rock, then contrasted to the traditional coal mining. The results showed that:in the processing of underground coal gasification and coal mining, the roof strata movement curve consistent with a negative exponential functions the sinking speed of coal gasification roof is faster than the sinking speed of coal mining, and vertical displacement is larger; the nearer from the roof, the greater of the vertical displacement, especially the direct roof displacement increases rapidly.

Research on the Affect of Groundwater on the Stability of the Slightly-expansive Soil Slope

DONG Zhu, MAO Yong, LAI Zhengfa

2010, 24(5): 231-234. doi: 10.3969/j.issn.1007-2993.2010.05.004

[Abstract](33) [PDF 343KB](4)

Abstract:
The groundwater is an important factor for the slope stability; the influence includes the intrinsic factor and the extrinsic factor. Generally speaking, the affect of intrinsic factor includes the gravity density and strength of the soil layer in the slope. Groundwater also may produce another additional force in slope soil, such as Buoyancy pressure, Hydrostatic Pressure, Hydrodynamic pressure, Penetration and so on, which are the extrinsic factor. Based on the study of every instability stage and every influence factor of a slightly-expansive soil slope, the conclusions are shown as below. The result is unsafe for the slope stability, if the analysis only includes the influences of groundwater on weight density of soil and shear strength. Especially, when the slope soil is a slightly-expansive soil, its strength will be reduced if it is wet. It should use the index of Water Immersion Test to check the stability of the slope, and the additional load should be considered, which is generated by the seep of groundwater.

The Exeriment and Study on Micropore Characteristic Influenced by Temperature

ZHANG Ping, FANG Yingguang

2010, 24(5): 235-238. doi: 10.3969/j.issn.1007-2993.2010.05.005

[Abstract](27) [PDF 263KB](3)

Abstract:
The Shenzhen soil and remolded bentonite was prepared after drying with drying method and freeze dry method, with the cumulative intrusion curve obtained form mercury intrusion test, gave the division of pore scale for soil according to the test result. The difference of soil prepared by drying method in different temperature and freeze dry method was analyzed, and draw the conclusion that when drying for soil sample using in mercury intrusion test, the freeze dry method was better than drying method.

The Technological Practice and Discussion on Integration of Drilling and Grouting

WU Xuxing, CENG Pengjiu

2010, 24(5): 239-242. doi: 10.3969/j.issn.1007-2993.2010.05.006

[Abstract](31) [PDF 302KB](4)

Abstract:
Grouting is composed by two independent processes, pore-forming and grouting. Pore-forming is composed by a suit of drilling tool and pipe while grouting composed by injection pipes. In some construction areas both drilling team and grouting team had to bring into operated. Pore-forming and grouting combined into one process can improve both quality and efficiency of grouting after process improvement. The principle of drilling and grouting integration technology and its technological process and characteristics were introduced in this paper and also the engineering practice was illustraied.

Relationship Between Water Content w and Unsaturated Soil Strenth Indices c and φ

LI Jinyu, YANG Qing, MENG Zhangjiang

2010, 24(5): 243-247. doi: 10.3969/j.issn.1007-2993.2010.05.007

[Abstract](26) [PDF 328KB](13)

Abstract:
It is proved that shear strength of unsaturated soil is related to matric suction. However matric suction has close relationship with water content. Based on the results of the laboratory test and theoretic analysis, the effect of water content on unsaturated soil shear strength indices c and φ is investigated. At the same time, the effect of matric suction on unsaturated soil shear strength indices c and φ is discussed by the soil-water characteristic curve(SWCC). Based on the tests,the value of c decreases as the value of water content w increases and the value of matfic suctionμ decreases. The value of φ has little change By linear regression analysis, the conclusions is indicated that cohesion has semilog linear relationship with water content and cohesion is directly proportional to matric suction. The precisions of the previous aren't satisfied and further research is needed. With the development of unsaturated soil mechanics, researches on unsaturated soil shear strength indices should be strengthened.

Failure Pattern of Reinforced Saline Soil with Wheat Straw and Lime

LI Min, CHAI Shouxi, DU Hongpu

2010, 24(5): 248-252. doi: 10.3969/j.issn.1007-2993.2010.05.008

[Abstract](28) [PDF 406KB](6)

Abstract:
Failure pattern of soil is the comprehensive expression for the magnitude and status of stress, and displays the microstructure characteristic from macroseopic view. Analysis on shear failure patterns of soil, that of saline soil, reinforced saline soil with wheat straw, lime-soil, and reinforced lime-soil with wheat straw, are carried out. Results present that:①Both saline soil and reinforced saline soil with wheat straw display the failure in plastic manner, which showing a typical swelling shape in saline soil. The lateral deformation of reinforced soil is far less than that of saline soil because of reinforcement function. ②Lime-soil and reinforced lime-soil with wheat straw are all plastic in early curing-day, and brittle in later curingday, however, the fracture surface of reinforced lime-soil is more irregular than that of lime-soil. ③Fracture of reinforeed soil in low confining pressure condition is more complex than that of in high confining pressure condition, because constraint force mainly comes from reinforced function in low confining pressure, but comes from reinforced and solidified function in high confining pressure condition. ④Reinforced function can constraint deformation, failure position always locate in the un-reinforced position as reinforcing in different areas. Reinforcement with wheat straw and lime can not only more effectively increase antideformation and strength of soil, but also solve the shrinkage crack problem of lime soil. As a result, it is an effective method to improve the saline soil by reinforced with lime and wheat straw.

Application of the Framework Composite-lining Structure on the Subsurface Construction

ZHANG Li, WANG Junjian

2010, 24(5): 253-256,266. doi: 10.3969/j.issn.1007-2993.2010.05.009

[Abstract](34) [PDF 575KB](3)

Abstract:
When the CRY) excavation method are used to tunneling large cross section, the horsehead-breaking of crosschannel is often the largest part of deformation, a reinforced structure of the architecture is required. There are three common practice inductions:to make Secondary-lining method, to make composite-lining method, to make reinforcement posted-beam method, this article analyzes the advantages and disadvantages of these three methods, and proposes the conception of the framework composite lining. Based on the Beihaibei Metro Station, using the load-structure model and the three-dimensional stratum model, from the strength, deformation, and risk prediction, this article demonstrates the feasibility of such strengthening measures.

Research on the Photo Source Stauroscope Examination Appliance

YU Defa, LIN Shiwen, GE Lianying

2010, 24(5): 257-259,271. doi: 10.3969/j.issn.1007-2993.2010.05.010

[Abstract](21) [PDF 302KB](3)

Abstract:
For heavy-caliber drilling axis of mud filled whether to achieve the design requirements, which needs to carry on the examination of the drill hole axis's verticality. However, the commonly used plumb bob ocular estimate estimation by eyes and the axis-line are the long-base method, which can not examine the drilling axis accurately whether to displace. Based on the barrel body test in the uniform application, makes the improvement to the traditional method. Use of the steel pipe isolation, the man-made space, and using principle that light to go straight, the vertical focusing which manufactured "photo source stauroscope examination appliance" that the synchronized distortion barrel body, in the tube shines, the mirror obviously point of intersection, metering equipment as drill hole spool thread central point. The experimental tests prove that the examination appliance satisfies the design requirements, thus examination question that the heavy-caliber drill hole filled with mud spool thread whether to displace is solved.

Application of EPB Jacking Pipe in DN 2400 Pipeline

LIU Yongsheng, YUAN Zhengzhong, MA Xuanlong

2010, 24(5): 260-263. doi: 10.3969/j.issn.1007-2993.2010.05.011

[Abstract](39) [PDF 331KB](3)

Abstract:
Earth pressure balance pipe jacking technology, it can be safely used for soil as shallow as 0. 8 times of OD. The authors introduced Huanggang Yi-ai Lake interception in dredging DN 2400 pipeline -test section (158m) of earth pressure balance pipe jacking successful practice. Through cases, adverse geological conditions of large diameter earth pressure balance pipe jacking technologies such as ground deformation control issues to explore. At present there is not yet the successful practice of the project in China. The success of this case will help to promote the construction of earth pressure balance pipe jacking technology, innovation and progress, for future similar projects with some guidance.

Analyze of Large Deformation of a Deep Foundation Pit in Beijing

LU Qingjian, ZHANG Zhiping, CHENG Xuejun

2010, 24(5): 264-266. doi: 10.3969/j.issn.1007-2993.2010.05.012

[Abstract](22) [PDF 211KB](7)

Abstract:
Deep foundation pit deformation control is very important in strict surrounding environment, base on a foundation case in Beijing, the reason of large deformation and the control method was introduced in this paper. It is proposed that all sorts of water and ex-supporting system should be taken into serious consideration during foundation pit design.

Controlling Technique for Disasters of Dump Landslide and Debris Flow

KAN Shenglei, SUN Shiguo, LI Xiaofang

2010, 24(5): 267-271. doi: 10.3969/j.issn.1007-2993.2010.05.013

[Abstract](32) [PDF 483KB](9)

Abstract:
FLAC3D simulate analysis of the breach pattern of the dump. Analyze the latent factor of the appearance of the dump and debris flow; combine with the specific project examples. Aimed at the disaster of the dump, stressing both prevention and management while with emphasis on prevention. Bring forward the techniques of the reversed waste disposal and the sloped delaminating waste disposal to improve the stabilization of the waste dump; Prevention and control the dump disaster with the combination of hill slope leading drainage and the bottom effusion system, which would provide some reference meaning to both the prevention and management of the waste dump disaster.

2010 Vol. 24, No. 5