2017 Vol. 31, No. 5

Development and Creation
Study on Stability Evaluation and Treatment Method of Rock Slope with High Rock Mass Adjacent to Building
Mu Weigang, Liu Huancun, Ma Yongqi
2017, 31(5): 217-220,245. doi: 10.3969/j.issn.1007-2993.2017.05.001
Abstract:
The paper analyzed the current characteristics of high rock slope and the predicament in treatment, summarized the advantages and disadvantanges of the quantitative evaluation of high rock slope stability. Taking a project next to the building of mountain slope as an example,it used strength reduction method to evaluate the slope stability, and studied the failure mechanism and form of mountain rock bedding high slope. With adaptation to local condition, the top of slope supporting structure selected the new GSS2 A active protection net system, the bottom of slope selected the foot wall and the arched frame masonry structure. The practice shows that the overall stability evaluation methods is suitable in the design of slope supporting, and the supporting structure is safe,economical and beautiful, convenient for construction. It provides reference for the similar slope treatment.
In-situ Anisotropy Testing Technology and Its Application in Engineering
en Wenfeng, Yan Zhijuan, Wang Shengyuan
2017, 31(5): 221-224,271. doi: 10.3969/j.issn.1007-2993.2017.05.002
Abstract:
The characteristics of anisotropy are considered to have important implications for stability evaluations of soft clay. A new type of test device and test method for in-situ anisotropy testing of soil are proposed, and the formulas of strength in the horizontal and vertical directions are given. In-situ shear tests of soft clay were conducted, to test the horizontal strength and vertical strength, as well as anisotropy ratio of soft clay. Meanwhile, the test result was used in the slope stability analysis. The results indicated that it is applicable to use the "double-vane" shear test to measure the horizontal strength and vertical strength of soft clay, the value of anisotropy ratio Sh/Sv is bigger than 1. And it is more reasonable to take account of anisotropy ratio into the slope stability analysis of soft clay.
Research on the Heave Correction of Transducer Using GPS-RTK Height
Gou Qitai
2017, 31(5): 225-228,257. doi: 10.3969/j.issn.1007-2993.2017.05.003
Abstract:
In the traditional mode for underwater measurement, the vessel generates unavoidably pitch, roll and heave by the water flow, wind, waves and other effects. These effects produce great error of bathymetric survey, but the error is difficult to eliminate because of the randomness of wave. The effect of heave can be eliminated by attitude instrument, but the equipment is not widely used in the coastal and inland river basins because of the high cost of the equipment. No tide sounding system can weaken the heave of transducer, but this method requires the normal height of every control points by leveling and the tide data. This paper analyzes the correction method and principle of the heave, and researches the signal of GPS-RTK height and how to extract the heave, and proposes the heave correction of transducer using GPS-RTK height which can weaken the heave, improve the accuracy in the bathymetric survey with tide.
Study on Redundancy Design of Soil Nailing Retaining in the External Angle of a Foundation Pit in Beijing
Wang Duli, Liu Beining, Shen Yupeng
2017, 31(5): 229-235. doi: 10.3969/j.issn.1007-2993.2017.05.004
Abstract:
Based on the Soil Nailing Retaining project in the external angle of a foundation pit in Beijing. By using Midas/GTS software, theexcavation model of the foundation pit is established, the redundancy of the support system is calculated by taking soil nail axial force and soil deformation as the standard, and the influence of reinforcement of waist beam and parameters of the external angle on redundancy of the foundation pit support system are analyzed. The results show: ①Compared with the no-waist beam system,displacements of the negative position in the external angle can be controlled positively by the soil nail-waist beam system. Also, the force transmission paths are added and the redundancy is improved. ②By using the soil nail-waist beam system, the axial force of nail near the external angle can be reduced, the dangerous components can be protected and the redundancy of bearing capacity can be also improved. ③The redundancy of supporting system is reduced with the external angle’s protruding length increase and the size of the external angle reduce.
Technology Probe and Research
Application of Quantitative Geological Strength Indexes in Evaluating Mechanical Parameters of Surrounding Rock Mass
He Weiwei
2017, 31(5): 236-239. doi: 10.3969/j.issn.1007-2993.2017.05.005
Abstract:
The determination of the mechanical parameters of surrounding rock mass is a difficult and key issue in tunnel engineering stability evaluation and numerical calculation. The geological strength index(GSI) is just a classification system for solving this issue. The quantitative method of GSI and Hoek-Brown criterion that estimates the surrounding rock mechanical parameters is introduced. Based on quantitative disturbance index D and absolute weathering index AWI,the surrounding rock mechanical parameters of a highway tunnel are evaluated. Under the condition of lacking in situ-test and plenty of sample data,this simple and practical method can accurately reflect the mechanical properties of jointed surrounding rock mass and given for reference of similar projects.
Application of Geotechnical Investigation Techniques in Dynamic Compaction of Expansive Soil Filling
Dang Zhirong, Zeng Guohua, Wang Ruihai
2017, 31(5): 240-245. doi: 10.3969/j.issn.1007-2993.2017.05.006
Abstract:
Using geotechnical engineering methods to resolve technical difficulties in construction processes may appears to be a common approach, geotechnical construction workers may found it challenging to apply such method to work due to their diverse backgrounds and lacking of experiences. Based on the analyses of the Geotechnical Investigation Report of a Plant in Yunnan Longling and on-site observations of the distinctive foundation soil expansion due to water absorption, this paper further discussed the component of the thick fill to be disposed and the characteristics of the expansive soil at the location. This paper also proposed a dynamic compaction approach of "compacting while removing, timely filling, case by case treatment" which can effectively resolve the construction difficulties caused by expansive soil during rainy season and the problem of unable to dispose large scale thick soil. The proposed approach will eventually shorten the construction period as well as reduce the cost which provides theoretical value and practical significance to similar projects.
The Analysis of an Engineering Example about Curtain for Cutting of Confined Water in a Foundation Excavation in Beijing
Liu Wu
2017, 31(5): 246-252. doi: 10.3969/j.issn.1007-2993.2017.05.007
Abstract:
The foundation pit is about 190 m long,98~195 m wide, and presenting the shape of "L". The base burying depth is different(the depth of the main body is 10. 4 m,the depth of the sections is 6. 48 m). Existing sinks greenbelt in the middle part of the east(5. 88 m deep),the project is divided into phase 2 construction. The foundation pit will be protected by using "φ600 soldier pile wall + soil nailing wall above the pile".The foundation pit excavation are influenced by diving water and confined water, using "φ1200 mm rotary jet and mixing cement-soil pile" between the adjacent pile of foundation pit protection. That will be biting with the pile of foundation pit protection to form a curtain for cutting off drain, and the diving water will be drainaged to clean within the curtain, the confined water below the basement nearby will be drainaged to clean within the curtain. In order to ensure that groove bottom of the main body foundation pit,and the elevator well bottom, and the sump pit are not to be outburst flood during excavation.
Study on Influence of Pipeline Displacement Caused by Foundation Pit Excavation
Li Xiangqun, Zhang Zhaohui
2017, 31(5): 253-257. doi: 10.3969/j.issn.1007-2993.2017.05.008
Abstract:
With the development of the foundation pit engineering in recent years,excavation cause changes in the surrounding environment and even the surrounding buildings, underground pipeline deformation or fracture damage accidents are common. So we should strengthen the research of foundation pit engineering, reduce the occurrence of such accidents. In this paper, by using the method of numerical simulation, during the process of excavation of foundation pit surrounding buried pipelines affected by excavation caused variation of pipeline displacement. This paper summarizes the influence of excavation displacement around buried pipeline,and put forwards some suggestions on the buried pipelines in the excavation process of foundation pit supporting.
Numerical Simulation and Prediction of Contaminated Groundwater in an Animal Protein Production Site by GMS
Zhang Yi
2017, 31(5): 258-262. doi: 10.3969/j.issn.1007-2993.2017.05.009
Abstract:
The groundwater flow and solute transport mathematical model was established based on FEMWATER module of GMS software according to the hydrogeological condition in Lai’an county, Chuzhou. The trend of migration and the environmental impact of CODCr and BOD in groundwater are predicted and evaluated under the abnormal working conditions in an animal protein production site. The results of numerical simulation show that the maximum migration of CODCr and BOD are 110 m and 135 m after 30 days in production area respectively, and the corresponding concentration are 1800 mg/L and 770 mg/L. In addition, the migration of CODCr and BOD are longer with high concentration under the absence of seepage prevention measures which resulting in a significance impact to the quality of phreatic water.
Study on Determination of Anti-floating Waterproof Level of a Building on Bank Slope
Tang Qiuyuan, Wang Xinglin
2017, 31(5): 263-267. doi: 10.3969/j.issn.1007-2993.2017.05.010
Abstract:
Under the condition of water level fluctuation, the seepage field analysis of the foundation pit on the bank slope plays an important role in determining the anti-floating water level. In order to analyze the change of groundwater level of the buildings on the bank slope under the condition of dynamic change of water level, this paper takes GeoStudio finite element software based on the saturated-unsaturated seepage theory. The numerical simulation of the finite element percolation of the bank slope is carried out. The variation law of the groundwater line under the rise and fall of the bank slope is analyzed, and the groundwater level line at the foundation pit of the building is obtained under the water level change condition. The relationship between the change from the slope to the horizontal distance of the edge of the foundation pit. Which provides a reliable basis for the anti-floating water level of the foundation pit on the bank slope. The calculation results can be used as an important reference data for the anti-floating design of the project, and the anti-floating stability analysis of the foundation pit is instructed.
Construction Technology Research of Soil Reinforcement Method When the Shield Tunneling Group Pile Foundation in Hangzhou Metro
Zhao Dong, Shi Zhending
2017, 31(5): 268-271. doi: 10.3969/j.issn.1007-2993.2017.05.011
Abstract:
It is dangerous for bridge traffic and subway tunnel construction when the shield machine crossing the bridge group pile foundation sections, because the soil is disturbed and transmission displacement of pile foundation. Hangzhou 1 Line Metro using second times grouting and steel pipe grouting technique, the slurry fully filled pores of soil in the end of shield, the soil becomes more stable, the field tests indicated that the lateral displacement of the tunnel close to pile reduced more than20 %. The average reduce of surface subsidence is 6. 1 mm, effectively ensured the safety of the bridge structure and the construction of the subway.