岩土工程技术

Study on Physical and Chemical Properties of Organic Mud and Its Engineering Application

Liu Huancun, Mu Weigang, Liu Tao

2017, 31(2): 55-61,71. doi: 10.3969/j.issn.1007-2993.2017.02.001

[Abstract](47) [PDF 5223KB](5)

Abstract:
This paper analyzes the wall protection mechanism of the common inorganic mud,propsoing the new concept of borehole wall protection organic mud,and study the relationship between the physical properties of pile borehole wall protection organic mud with the amount of HPAM by the laboratory comparative experiments,and the degradation process of HPAM,and the organic mud used in bored pile of pepple stratum in Chengdu.Through the laboratory experiments and the practical engineering application,a comprehensive analysis of the advantages and disadvantages of different clay content of organic mud,proposing the organic mud ratio applicable to the borehole wall protection,and do thorough analysis of the degradation and enviromental protection of organic mud,it is concluded that organic mud is degradable,providing a new way for the construction of the bored pile wall protection.

Research on the Influence of Ground Water on the Bearing Capacity of Residual Soil

Liu Junlong

2017, 31(2): 62-66,96. doi: 10.3969/j.issn.1007-2993.2017.02.002

[Abstract](53) [PDF 1052KB](10)

Abstract:
The physical and mechanical indexes of residual soil in natural state and in saturation state on seven sites were obtained by the soil tests,based on the formulas of code for design of building foundation and the formulas of Terzaghi ultimate bearing capacity foundation,the influence on the bearing capacity of residual soil due to the state of ground water are analyzed,the decreasing range of the bearing capacity of residual soil after soaking by water may descend 2.8 to 58.8 percent.The results of twelve loading tests indicate that,the characteristic value of subsoil bearing capacity of the residual soil after short time and long time soaking by water decreased obviously,the decreasing range can reach 11 to 57.5 percent.

Experimental Study and Finite Element Analysis on Rebound and Recompression of Clay Due to Foundation Excavation

Wang Lu, Zhang Qichang, Wang Xiaobo

2017, 31(2): 67-71. doi: 10.3969/j.issn.1007-2993.2017.02.003

[Abstract](54) [PDF 2489KB](6)

Abstract:
Based on rebound recompression test of different soils,the deformation characteristics of soil samples under unloading were studied.The existing research results were verified.Meanwhile,build layer models by using finite element analysis software Midas GTS NX,after the process of loading-unloading-reloading,the settlement values under different working conditions were obtained.The results may provide useful reference for similar projects.

The Calculation and Application of PHC Pipe Pile in Collapsible Loess Foundation

Yang Runtao

2017, 31(2): 72-75. doi: 10.3969/j.issn.1007-2993.2017.02.004

[Abstract](51) [PDF 966KB](8)

Abstract:
PHC pipe pile in collapsible loess area has been widely used,for the characteristics of PHC pipe pile and the calculation of bearing capacity in the collapsible loess,introduce the concept of friction neutral point.With a complete design and calculation is based on the engineering example of data and field test,the design of PHC pipe pile in collapsible loess foundation calculation and test carried on detailed analysis,research and discussion,and will be the basic form and the other basic is used for economical comparison.

Brief Discussion on the Determination Method of Foundation Bearing Capacity of Neogene Mudstone

He Jiankai

2017, 31(2): 76-79,90. doi: 10.3969/j.issn.1007-2993.2017.02.005

[Abstract](74) [PDF 770KB](26)

Abstract:
As a classical soft rock,mudstone is easily affected by external factor such as water or long-time exposed,etc,and then its physical and mechanical properties will be changed.As an important engineering property,the determination method of bearing-capacity is one of the most important tasks.For soft rock,a variety of testing method should be adopted to confirm the bearing-capacity of foundation.In this paper,the investigation experience of a nuclear power project in Neogene mudstone area is used to analyse and compare the variety method which usually used to gain the bearing-capacity of soft rock foundation.

Experimental Research on Basalt Residual Soil Ground by Dynamic Consolidation at Haikou Meilan International Airport

Xie Shuling, Yang Yongkang, Ding Xuewu

2017, 31(2): 80-85. doi: 10.3969/j.issn.1007-2993.2017.02.006

[Abstract](53) [PDF 2055KB](5)

Abstract:
Based on the ground treatment of Haikou Meilan International Airport Extension Project,the geotechnical characteristics of basalt residual soil which widely distributed in the airfield area are summarized,typical area is chosen as the ground treatment test section before large area ground treatment,the design and test plan are discussed by dynamic consolidation.Through the data analysis of tamping settlement monitoring,surface settlement monitoring,static penetration test,standard penetration test and heavy dynamic probe test,ground reaction modulus test,solid volume rate test,dry density test,laboratory soil test and post-construction settlement monitoring,reinforcement effect by dynamic consolidation are analyzed,the suggestions of partition ground treatment,backfill crushed-rock layer parameters,effective improvement depth,stop tamping standard and post-construction settlement monitoring are proposed,which provide a scientific basis for the design and construction of subsequent large area ground treatment.

The Comparative Study on Laboratory Direct Shear Test with In-Situ Shear Test of Mechanical Characteristics on the Soil-Rock Mixture

Yao Binke, Li Youming, Liu Changqing

2017, 31(2): 86-90. doi: 10.3969/j.issn.1007-2993.2017.02.007

[Abstract](49) [PDF 3353KB](10)

Abstract:
The soil rock mixture is a kind of special geological medium formed by soil mixed with irregular rocks,widely distributed in the mountains and had a greater influence to the road and tunnel engineering construction in mountainous area.Because of its particularity,its mechanical property is not easy to find out,which affect on the accurate evaluation,it may cause the waste of engineering cost or improper handling to cause the potential risk of the project.This paper combined with a typical soil rock mixture in TiZi tunnel project of XingYan highway,conducted three groups level shear test in-situ and two groups direct shear test,revealed the mechanical properties of this heterogeneity,inhomogeneous geological medium,by comparing with the in-situ test and laboratory test results,comprehensive analysed and evaluated the Shear strength index of the soil rock mixture,fully emboding the necessity of the in-situ testing work in solving the practical engineering problems.

Study on New Technology and Application of Foundation Treatment

Pan Tingting

2017, 31(2): 91-96. doi: 10.3969/j.issn.1007-2993.2017.02.008

[Abstract](134) [PDF 1051KB](25)

Abstract:
Foundation treatment is a construction project in a universal technology,expansion of the construction scale of the project and the construction of the speed to accelerate and promote the vigorous development of foundation treatment technology.In recent years,the emergence of a series of new foundation reinforcement technology,such as vacuum surcharge preloading,well point dewatering,pile net composite foundation,strengthening microorganism and grouting technology and other new technologies.It briefly introduces the several foundation treatment new technology basic principle,application condition in engineering and construction technology,the research progress of ground treatment technology is summarized.Expectations of engineering and technical personnel to participate in the construction benefit,on foundation treatment technology innovation and development help.

Analysis of the Influence of Underground Civil Air Defense Channel on the Surrounding Buildings

Wen Weiguang, Zhou Yuming, Li Chao

2017, 31(2): 97-99,104. doi: 10.3969/j.issn.1007-2993.2017.02.009

[Abstract](47) [PDF 1988KB](6)

Abstract:
In order to analyze the influence of underground civil air defense channel on the surrounding buildings,according to the geological conditions of site engineering,we followed the comprehensive analysis method to determine the settlement influence scope of civil air defense channel using the Peck,Plaxis,ABAQUS.The results show that the numerical calculation is consistent with the on-site investigation.The study has a certain reference significance for the analysis of the influence of underground construction on the surrounding buildings under the similar conditions.

Early Warning and Stability Analysis of the Wuxizuo Tunnel Based on the Monitoring Data

Zhang Jun, Liu Yuan

2017, 31(2): 100-104. doi: 10.3969/j.issn.1007-2993.2017.02.010

[Abstract](43) [PDF 2942KB](6)

Abstract:
Tunnel monitoring,being the core of New Austrian Tunneling Method,has become an essential factor in the construction of the tunnel.It provides accurate and timely basis for evaluating the feasibility of construction method,the rationality of design parameters and understanding of the actual level of surrounding rock and its deformation characteristics.In order to ensure the safety of the tunnel construction,the data of vault subsidence,peripheral convergence,and the surface subsidence were analyzed for the Wuxizuo shallow bias tunnel section,and timely warning of the hidden risk was proposed after that the reinforcement measure of the temporary inverted arch and encryption steel arch was taken timely to.secure the stability of surrounding rock and prevent the hidden danger of collapse.The result of analysis and treatment measures provide reference for similar projects.

Analysis and Processing Scheme of Local Instability for Flowing Sand in Some Foundation Pit

Zhang Kai, Feng Keming

2017, 31(2): 105-109. doi: 10.3969/j.issn.1007-2993.2017.02.011

[Abstract](55) [PDF 7988KB](10)

Abstract:
Aiming at the phenomenon of flowing sand in deep foundation pit engineering,we study the reason that the local instability of slope caused by quicksand and the measures to deal with it according to the concrete case of a deep foundation pit in Beijing.The study shows that there are a lot of factors which influence the flow sand phenomena,such as grain composition,structure,burial condition and quality problem of the process of construction.The first is blocking the seepage path of hydrodynamic pressure,such as waterproof curtain,steel sheet pile,gravel or pebbles after the wall and so on.The second is reducing the head difference of the inside and outside and the hydraulic slope,such as light well dewatering,waterway drain with draft tube.Through analyzing the concrete engineering case,it can solve the flow sand with adjusting measures to local conditions as well as learning for the similar project.

2017 Vol. 31, No. 2