岩土工程技术

The Application of Precise Trigonometric Leveling in Foundation Pit Monitoring

Sun Yuanping, Yao Peijun, Liu Hongchen

2013, 27(4): 163-166,195. doi: 10.3969/j.issn.1007-2993.2013.04.001

[Abstract](47) [PDF 1744KB](6)

Abstract:
Geometric geoid method is the conventional method of foundation pit vertical displacement monitoring. This method is strongly influenced by the environment of foundation pit construction site. It is hard to measure in some narrow space foundation pit engineering. In this paper, the characteristics of three trigonometric leveling methods were summarized, and the source of measuring error and accuracy of total station precise trigonometric leveling was studied. Combining with engineering survey test, the measurement accuracy of TCA2003 total station precise trigonometric leveling was discussed. Then the feasibility and reliability of substituting precise trigonometric leveling for second-order leveling was analyzed. Finally, the process and condition of the application of total station precise trigonometric leveling were put forward.

Field Water Immersion Test on Expansive Silty Clay in Benguela,Angola

Liao Yanhong, Tang Guoyi, Liu Zhenghong

2013, 27(4): 167-170,207. doi: 10.3969/j.issn.1007-2993.2013.04.002

[Abstract](48) [PDF 1466KB](4)

Abstract:
The alluvial or diluvial silty clay around Benguela GRASA in Angola has the properties of swelling. Because of the very low water content, it is too dry to fetch the undisturbed sample, but the laboratory index from disturbed samples such as free swell and atterberg limits may distort the real facts. So it is necessary and helpful to adopt field water immersion test for ascertaining the swelling properties. The results of the field test indicated that the laboratory results have limitations and mistakes to determine the swelling properties; the silty clay has a high potential of swelling because of low water content; while increasing the water content, the soil has high swelling deformation and expansive force; the deformation curve of the plate shows subsoil heave is sensitive with small fluctuation of moisture content; but, the strength would fall fast if the water content increase more, the Benguela silty clay has obvious sensitivity to water with the phenomena swelling and weakness during water content increasing.

Field Test Study on MJS Method Reinforcing Timber Pile Foundation Located at Ancient Seawall

Wang Yongwen, Bao Zengjun, Zhang Kaiwei

2013, 27(4): 171-175. doi: 10.3969/j.issn.1007-2993.2013.04.003

[Abstract](41) [PDF 1568KB](8)

Abstract:
The high-pressure jet method, MJS, was applied in the reinforcement of the timber pile foundation located at Ming-Qing ancient seawall based on the research subject on protecting ancient seawall of Qiantang River from flood. In order to investigate the performance properties of timber pile foundation reinforced by MJS method, the monitoring on the deformation of seawall and tests on the treatment effect were carried out on the field. The deformation monitoring includes the settlement and horizontal displacement of seawall, while the tests on the treatment effect consist of the cone penetration test and single-pile static load test. The deformation monitoring shows that the settlement of seawall reinforced by the MJS is small, however, the horizontal displacement is obvious. The tests indicate that the diversity of the radius of pile constructed by MJS method is more than 1.5m; the mechanical strength of soil is obviously improved; the slope of the load-settlement curve of the reinforced timber pile is slowed down, while the bearing capacity of singe timber pile is increased by more than 60%.

The Studies of Geographic Information System-Based Mapping Integration

Li Baojia, Hu Nan, Chen Lei

2013, 27(4): 176-179. doi: 10.3969/j.issn.1007-2993.2013.04.004

[Abstract](37) [PDF 1128KB](4)

Abstract:
The paper contains a brief introduction of surveying and mapping integrated development profile as a summary. An example to the project of rural collective land ownership in Yang Gao, Shanxi Province, the content explores the link of organic integration under which it implements the construction of cadastral survey and data acquisition integration between database establishment of geographic information systems and the traditional integration. what's more, a study discusses the integration of the interactive collaboration of the geographic information systems and data acquisition entry staff. Thus, thinking about the balanced development of the human-computer interaction so that it can promote the integration of Surveying and Mapping technology building better.

The Application of Development Technique Based on Excel VBA in Borehole Wave Velocity Test Results Table

Yang Cangsheng

2013, 27(4): 180-183. doi: 10.3969/j.issn.1007-2993.2013.04.005

[Abstract](31) [PDF 3075KB](6)

Abstract:
Using the Excel computation ability and Excel VBA macro language increase automatic function in spreadsheet, in order to solve the problem of borehole wave velocity test results analysis, and make the achievement information quick and easy, verified in engineering practice.We introduced the characteristics and attentions of the developing series through many aspect, the working table of software engineering design,data flow design,module design,the operation command design, system running environment results of graphic design principles and skills and so on.

Numerical Analysis on Effect of Water Seepage in Foundation Pit Nearby Metro

Ceng Qingguo, Xu Jianmin

2013, 27(4): 184-187. doi: 10.3969/j.issn.1007-2993.2013.04.006

[Abstract](43) [PDF 2445KB](6)

Abstract:
Based on the computing method of seepage-stress coupling and seepage analysis function of MIDAS/GTS, two-dimensional Numerical analysis of effect of water seepage in foundation pit near metro structure is study in this paper. The results are the method of "diaphragm wall+ inner support+ waterproof curtain" used in foundation pit support near to metro, can control subway sedimentation caused by water seepage during excavation effectively. Moreover, pore water pressure reduction and maximum sedimentation of the bottom of tunnel present parabolic trend with increasing excavating depth.

Simulation and Field Measurements for Combination Support of Soil Nailing and Pile-anchor

Zhou Yuqi, Liu Bo

2013, 27(4): 188-190,200. doi: 10.3969/j.issn.1007-2993.2013.04.007

[Abstract](70) [PDF 2125KB](6)

Abstract:
The combination support of soil nailing and pile-anchor is a common type of deep foundation pit supporting form in Beijing area. It is safe and low cost. In the design of previous engineerings, People do not consider the soil nailing and pile-anchor of the two different support type interactions, then it cause easy the scene safe hidden trouble.Based on the numerical simulation methods, combining CWTC IIIA deep foundation excavation in-situ monitoring data, we got a related law of the combination support and given in engineering practice of simple control method.

Research on Mechanism and Analysis of Underground Pipeline Detection with Ground Penetrating Radar

Su Zhaofeng, Chen Changyan, Xiao Min

2013, 27(4): 191-195. doi: 10.3969/j.issn.1007-2993.2013.04.008

[Abstract](57) [PDF 1289KB](5)

Abstract:
The dielectric constant and electical conductivity of underground pipeline are obviously different with surrounding medium,regardless of its internal filling air,water or other medium.It is prerequisite with the ground penetrating radar for detecting underground pipelinse.This paper analyzes the ground penetrating radar for detecting underground pipelines polarity.Through the establishment of metal and non-metallic pipeline forward numerical model, it focuses the transimission mechanism of GPR electromagnetic wave in metal pipeline,nonmetal pipeline. Combined with the actual detection of underground pipeline ground-penetrating radar feature mapping,it analyzes the spectrum characteristics from the reflection waveform,polarity,phase axis,electromagnetic wave energy absorption and attenuation.Finally,it establishes the identificaion method of GPR detecting metal and non-metallic pipeline.The results play a very good guidance for accurately detecting underground pipelines.

The Shear Strength Damage-Characteristics of Yunnan Lateritein Soaking Condition

Deng Xin, Huang Ying, Liu Peng

2013, 27(4): 196-200. doi: 10.3969/j.issn.1007-2993.2013.04.009

[Abstract](56) [PDF 1123KB](8)

Abstract:
The engineering properties of laterite had affected seriously in the condition of immersion which result in shear strength reduction. The factors of soaking time, initial water content, and initial dry density were considered.It goes direct shear test to study of immersion on the shear strength of laterite. The test results show that:the initial dry density is larger and the initial moisture content is smaller, soil shear strength reduction is greater.With soaking time, the laterite with different initial dry density or initial moisture content have different change trend on shear strength.Damage-coefficient is a measure of damage effect of shear strength in soaking condition.After immersion in lateritic samples under the softening and dissolving action of water, bring among soil particles cementation severely damaged, cohesive force decreased dramatically;Meanwhile shear test produces instantaneous compression and deformation.The original pores of laterite was filled. Laterite particles of joining-up degree is improved.Particle dislocation is relatively more difficult.The angle of internal friction increased slightly.

Application of Computerized Tomography in Evaluation on Self-healing Performance of Compacted Bentonite

Chen Jie, Zhang Yonghao, Shen Zhong

2013, 27(4): 201-207. doi: 10.3969/j.issn.1007-2993.2013.04.010

[Abstract](37) [PDF 4749KB](5)

Abstract:
After Penetration test, computerized tomography was carried on to evaluate the self-healing performance of compacted bentonite. By contrasting the CT number, CT variance and CT images of the fracture zone and the control zone in cross-section to analyse the CT characteristics in soil. The results showed that under confined conditions, the soil expanded upon imbibing water, internal voids narrowed, macro cracks and connectivity pores disappeared. Meanwhile, CT number of the fracture zone was lower than the control zone, CT variance was on the contrary. All the data above showed that the compacted bentonite has good self-healing performance, although fracture has certain influence on structure of healed samples.

The Investigation Research on Underground-harmful-gas of Metro Engineering

Wang Zenghui, Huang Wei, Ma Pengyuan

2013, 27(4): 208-212. doi: 10.3969/j.issn.1007-2993.2013.04.011

[Abstract](39) [PDF 3450KB](7)

Abstract:
The underground-harmful-gas is one of the typical natural hazard of metro construction. In the engineering practice, the best way is to exhaust the harmful gas in advance. In this article, we will show you a way on how to survey on underground harmful gas which based on our engineering practice and statistics, so we can have the accurate information about the burial depth, distribution range, components and variation of the harmful gas. Besides, we will propose the measures can taken to tackle the problem in construction and later stages of construcion to ensure the Project can carry smoothly.

Geotechnical Engineering Problems and Treatment over Beijing Shallow Mountain Area Construction Site

Hao Bing, Wang Qing, Ren Zhishan

2013, 27(4): 213-217. doi: 10.3969/j.issn.1007-2993.2013.04.012

[Abstract](28) [PDF 3180KB](8)

Abstract:
Beijing's urban construction has been gradually extended to mountain area. The complex nature geological conditions and engineering geological conditions of the shallow mountain put forward higher requirements of geotechnical engineering investigation and evaluation. In this paper, according to the actual engineering from the engineering geological characteristics of the shallow mountain, the topography, landfrom, formation lithology and lithology substance component, bad geology function and engineering geological conditions is analyzed The engineering geological problems of the shallow mountains are slope stability, uneven settlement under complicated geological conditions, and special soil. Design should be based on the geotechnical engineering condition, and avoiding the formation of high and steep slope, reducing the difficulty and cost of foundation treatment and other aspects optimization design, attention to surface drainage measures and environmental protection.According to the uneven ground treatment methods are mainly structural measures, artificial replacement foundation, composite foundation, pile foundation.

2013 Vol. 27, No. 4