2017 Vol. 31, No. 3

Development and Creation
Experimental Study on Static Load Bearing Capacity of Screw Piles in Collapsible Loess Area
Gao Jianzhong, Zhang Ruisong
2017, 31(3): 109-114. doi: 10.3969/j.issn.1007-2993.2017.03.001
Abstract:
Through the static load test of the bearing capacity of the screw piles of high-rise buildings in the collapsible loess area of Yan’an New Area,it is shown that the screw piles have the characteristics of friction-end bearing pile and the bearing capacity of single pile is higher.Under the same geological conditions,the increase of pile length after a certain depth has little effect on the bearing capacity of pile.As the screw pile in the loess area has a high bearing capacity,low pollution,economic and reasonable advantages,the process in Yan’an New Area of collapsible loess excavation area has a good prospect.However,there are few researches on application of screw pile technology in the excavated and filled areas of collapsible loess in Yan’an New Area.In the future application,it is suggested to analyze and study the influence factors of side resistance and end resistance of screw pile and the calculation method of bearing capacity.
Design and Implementation of Karst Survey Information System of Tangshan City
Nie Qingke, Li Jianpeng, Jia Xiangxin
2017, 31(3): 115-118. doi: 10.3969/j.issn.1007-2993.2017.03.002
Abstract:
Karst survey information system of Tangshan was developed using mapscope which is a GIS technology platform.The system can accomplish online query and management of karst survey information,and provide reference for urban construction planning and survey,construction and design of new project.The main differences between the present system and similar software are integrated applications of survey information about northern karst,supporting internet on-line operation and good expansion perfermance.
Fiber Reinforced Soil Shear Strength of the Experiment Research
Zhang Jun, Guo Kaiyue, Fu Hongmei
2017, 31(3): 119-124,129. doi: 10.3969/j.issn.1007-2993.2017.03.003
Abstract:
This paper studied different water content and different fiber content and different degree of compaction of fiber reinforced loess cohesion,internal friction angle and shear strength variation by direct shear test.The results show that:the moisture content increased from 14%to 18%,the cohesion of loess decreases when it is greater than 20%,the cohesion decreases rapidly;when the moisture content is 18%,the maximum internal friction angle and the shear strength reaches the maximum value;fiber materials in the surface,mesh and clumped distribution in loess soil,cohesive strength and internal friction angle increases with increasing fiber content increased first and then decreased.The amount of fiber is 0.5%of the optimal amount of fiber;fiber content is less than the optimal amount of fiber,increase the small change of internal friction angle with the degree of compaction,when the fiber content is larger than the optimal amount of fiber,the internal friction angle changes greatly;at the same time,in the actual application in this experiment,the relationship between moisture content,fiber content and compaction degree,internal friction angle and cohesive force is given,which is of guiding significance to the construction of loess area.
Deformation Control and Its Countermeasure of Embankment Slope in Deep and Thick Soft Foundation
Huang Weida
2017, 31(3): 125-129. doi: 10.3969/j.issn.1007-2993.2017.03.004
Abstract:
In combination with a deep soft soil embankment slope engineering instances,the reinforced soil retaining wall was proposed to support the slope.The stability and deformation of the reinforced soil retaining wall was analyzed by using the finite element analysis methods.Then the work characteristics of reinforced soil retaining wall and the countermeasures to avoid deformation were discussed.The results show that the reinforced soil retaining wall which have low requirement of bearing capacity and uneven settlement deformation can be used to soft soil foundation.CFG pile can transfer the upper structure load to the deep soil,which can effectively improve the bearing capacity and control the settlement of the foundation.Under the condition of soft soil foundation,the reinforced soil retaining wall should be preferred.Research results can provide guidance for similar slope engineering design.
Deep Foundation Pit Technology
Analysis of Monitoring Data over the Construction Period of the North Anchorage Foundation Pit of Fuma Yangtze River Bridge at Wanzhou District,Chongqing City
Ran Tao, Mei Songhua, Tan Lihua
2017, 31(3): 130-136. doi: 10.3969/j.issn.1007-2993.2017.03.005
Abstract:
The surface soil layer at the north bridge area of Fuma Yangtze River Bridge is characterized of great thickness and low strength,the underlying pelitic rock mass is highly sensitive to water,and thus the stability of the natural slope is relatively poor.In order to ensure the construction safety and perform feedback analysis of the north anchorage foundation pit,systematic safety monitoring had been carried out during the construction period of the foundation pit.Monitoring results showed that,shallow deformation and failure was easily triggered by rainfall in top soil layer at the periphery of the foundation pit,resulting in the displacements of several monitoring points exceeded the alarm value.Fortunately,deformation of peripheral slope had been effectively controlled after the completion of shotcrete-rockbolt protection.Displacement of the retaining pile increased rapidly when the fully and strongly weathered strata were excavated,while the displacement increased slowly when the moderately weathered stratum was excavated.The surficial and deep horizontal displacement of support structure did not exceed the alarm values at last.The prestress of cable changed smoothly during the construction period,and the accumulative variation of the prestress was far less than the alarm value.Monitoring results comprehensively reflect that the side-wall and the support structure of the north anchorage foundation pit were in a state of safe and stable.Meanwhile,the reasonability of the conditions and parameters adopted in the stage of engineering design had been verified.Furtherly,research results in this paper can help accumulate experience for similar excavation engineering in respect of design,construction and monitoring.
Application of Gantry Anchor Piles Supporting Structure in Deep Foundation Excavation with Soil-Rock Dualistic Structure
Zou Chaoqun, Liu Huancun, Ma Yongqi
2017, 31(3): 137-141,148. doi: 10.3969/j.issn.1007-2993.2017.03.006
Abstract:
Taking typical soil-rock dualistic structure geological conditions in Fujian region as background,this article analyzed and compared for selection of retaining and sealing scheme of deep foundation pit,introduced the approximate design and calculation method of gantry anchor pile in soil-rock dualistic structure.According to the field deformation monitoring results of foundation pit,gantry anchor piles supporting system is practical in soil-rock dualistic structure geological conditions;has obvious advantages of effectively control the deformation of foundation pit,constructing in limited space and geological conditions which is not applicable to construction of anchor etc;provides reference for the design of deep foundation pit supporting in the area of similar soil-rock dualistic structure geological conditions.
Study on Effect of Section Stiffness on Pile-anchor Retaining Structure
Zhang Huaiwen
2017, 31(3): 142-144,152. doi: 10.3969/j.issn.1007-2993.2017.03.007
Abstract:
Based on the construction of a project in Beijing,behavior mechanism and deformation properties of pile-anchor structure are obtained in this article by using theoretical method and orthogonal test analysis.Some suggestions that how to optimize the pile section on foundation pit supporting design are given here.A FLAC3D model is built nextly,the above conditions are carefully verified again.At last,according to the monitoring data,it takes the conclusion that the pile-anchor structure optimized section can assure the pit safety with meeting requirement of national standards.
Technology Probe and Research
Failure Mode and Stability Analysis of Rock Slope in Haiyang Nuclear Power Plant
Duan Yongkun
2017, 31(3): 145-148. doi: 10.3969/j.issn.1007-2993.2017.03.008
Abstract:
The stability analysis of the rock pit slope belong to Nuclear island in Haiyang Nuclear Power Plant is carried out by qualitatively and quantitatively.There is a large-scale hoisting equipment with large loading load on the top edge of the rock pit slope.The strike of the slope is cambered.Firstly,according to the stratum lithology and geological structure features of the site,the plane sliding,wedge failure and toppling failure of the slope are qualitatively analyzed by stereographic projection.The range and mode of failure may be determined preliminarily.On this basis,the means of the limit equilibrium,the stability of the plane sliding and wedge failure mode is analyzed quantitatively.The limit equilibrium is also used to analyze the stability of the slopes reinforced by anchors.Stated thus,the different failure modes may occur in different slope areas.The probability of occurrence of wedge failure is the greatest.The effect of the anchor rod on the stability of the wedge is obvious,especially for the less stable ones.
Reinforcement of Massive Cast-in-place Piles Accident in Karst Area
Lv Wenlong
2017, 31(3): 149-152. doi: 10.3969/j.issn.1007-2993.2017.03.009
Abstract:
When the cast-in-place piles construction occurs in karst area,the vertical bearing capacity of massive cast-inplace piles fail to meet the design requirements due to the caves under the piles.Therefore,this thesis discusses a rigid and semi-rigid composite foundation method,mixing the former cast-in-place piles are taken as the rigid piles with the latter longspiral piles are taken as the semi-rigid ones,which successfully avoids the piles accident.
Discussion on Slope Stability Analysis Method
Zhang Ming, Wang Dafeng, Hu Ronghua
2017, 31(3): 153-159,163. doi: 10.3969/j.issn.1007-2993.2017.03.010
Abstract:
The method of slope stability analysis was divided into deterministic and nondeterministic analysis method.The deterministic analysis method was divided into limit equilibrium method and numerical method,which of the former was some typical representative with Sweden Arc method and simplified Bishop method;which of the latter was some typical representative with finite element method and finite difference method.The nondeterministic analysis method was some typical representative with reliability method,fuzzy comprehensive judgment method,grey system method,artificial intelligence method.The principle,advantages and disadvantages and applicability of each method were described in detail,and some methods were compared and analyzed.Finally,the development direction of the stability evaluation of the rock and soil slope system was proposed.
Analysis on Causes of Building Cracking above a Coal Mine Roadway
Wang Chuan, Zhang Jihong, Zang Rui
2017, 31(3): 160-163. doi: 10.3969/j.issn.1007-2993.2017.03.011
Abstract:
The building cracking is caused by development of mining production and mining area construction burden on mineral enterprises,but not all building cracking is caused by mining production which aboves roadway or gob.The cause of building cracking above a coal mine roadway in Shaanxi province has been analyzed in this paper,points out the real reason is collapse deformation of foundation and groundwater drawdown of the site,but not the excavation of roadway.The conclusion of this paper is beneficial for the work of restoring,also can reduce unnecessary expenses of the coal mine,and this paper could provide reference for the similar projects.