岩土工程技术

Vertical Bearing Capacity Test of Bridge Pile Foundation and Numerical Simulation Analysis of Pile-soil Interaction

Sun Yuhui, Zhang Hui, Chen Changyan, Liu Guo, Yao Tianbao

2020, 34(6): 311-315. doi: 10.3969/j.issn.1007-2993.2020.06.001

[Abstract](130) [PDF 2191KB](41)

Abstract:
The pile foundation test of a high-speed bridge in Beijing is introduced as an example, including axial force, displacement monitoring design and monitoring data analysis method during test process. The pile side resistance, pile end resistance and pile foundation ultimate load of each layer of soil under the stratum conditions are obtained. Various parameters for friction pile design are also provided. Based on pile foundation test monitoring data, the numerical simulation method is used to analyze the failure load of pile foundation, evaluate the rationality of pile foundation design parameters, and optimize pile foundation design parameters such as pile length and post grouting. The mechanism of pile-soil interaction during pile foundation test is summarized, which provides reference for engineering experience for similar projects.

Research on Construction Methods of Deep Mixing Column Based on Remote Monitoring System

Chen Yi, Hu Weidong, Xu Yuan, Ye Guanbao, Shen Honghui

2020, 34(6): 316-320. doi: 10.3969/j.issn.1007-2993.2020.06.002

[Abstract](92) [PDF 2430KB](22)

Abstract:
As a commonly-used ground improvement alternative, deep mixing method can effectively increase the bearing capacity and reduce deformation of soft clays. However, quality control has still been a problem and there has been limit effective measure in practice. An application of remote monitoring system of deep mixing construction process is introduced, which is used in the ground improvement project at Huzhou Section in Hangzhou beltway, realizing real-time tracking and feedback of data during construction. Based on the monitoring data and standard penetration test, some kinds of typical construction method in the field were analyzed, and some guidance was offered for construction.

Application of Pit Dividing Technology in Deformation Control of Deep and Soft Clay Saturated Foundation Pit

Yang Yujiang, Shao Yaping

2020, 34(6): 321-324,328. doi: 10.3969/j.issn.1007-2993.2020.06.003

[Abstract](80) [PDF 1575KB](29)

Abstract:
Taking the deep and large foundation pit adjacent to a subway station in Suzhou as an example, the deformation caused by the deep and large foundation pit is controlled by using the principle of time and space effect and the pit dividing technology, and the safety of the close subway station has been guaranteed. The measured data of the surrounding environment are collected and analyzed. In the saturated soft clay area, based on reasonable pit division construction technology, the deformation of deep and large foundation pit during excavation could be controlled and the surrounding environment could be protected.

Quality Control Index for Contact Clay in Core Wall Dam of Miaowei Hydropower Project

Meng Yongxu, Dong Yufan, Yin Fei, Chen Liang, Wang Yongming

2020, 34(6): 325-328. doi: 10.3969/j.issn.1007-2993.2020.06.004

[Abstract](69) [PDF 825KB](7)

Abstract:
In the hydropower and water conservancy projects, the quality of contact soil is usually judged by the plasticity index and clay content. The plasticity of the soil depends on the type and content of highly hydrophilic clay minerals in the clay particle, which are capable of physicochemical interaction with water. The greater the plasticity index, the worse the water stability of the soil. Through analysis, the definition of the plasticity index and clay content of the contact soil in the current standard is not reasonable. The plasticity index I_p=10~26 and the activity index A_c=0.75~1.25 are proposed as the quality control indicators for contact soil materials. The clay content of soil materials for the Miaowei hydropower station is lower than the requirements of the specification, but the activity index A_c is calculated to be 1.08~1.25, which meets the requirement of activity index, so that it can be used as contact soil. After the Miaowei hydropower station was put into operation, according to the monitoring data, the displacement of the contact clay soil on both sides of the bank was small and no plastic failure occurred, which proved that the proposed control index is feasible.

Design and Practice of Soil Landslide Treatment Project Adjacent to Buildings

Wei Haitao, Sun Lanning

2020, 34(6): 329-333. doi: 10.3969/j.issn.1007-2993.2020.06.005

[Abstract](91) [PDF 3251KB](35)

Abstract:
A landslide project located in Mentougou, Beijing is mainly composed of artificial fill and coarse-grained mixed soil. Due to the excavation of the slope foot and the infiltration of surface water, the crack and deformation of the slope top are continuous expanding obviously, forming a traction landslide. Based on the analysis of the landslide characteristics and causes, inversion calculation of the shear test parameters is conducted on the basis of physical test, and limit equilibrium method is used to analyze the stability of the landslide. Anti-slide pile + top of cutting micro-pile + slope anchor rod lattice structure solution is proposed as a kind of comprehensive treatment measures to solve the landslide problem. After the treatment, the landslide deformation is controlled, and buildings near the road and slope-foot are protected. Good social and economic benefits have been achieved, at the same time it is expected to provide certain reference for similar disaster control project.

Study on Deformation Control of Single Floor Basement Pit near Shallow Foundation Building

Yuan Ziqi, Cui Yunliang

2020, 34(6): 334-338. doi: 10.3969/j.issn.1007-2993.2020.06.006

[Abstract](46) [PDF 3240KB](18)

Abstract:
In order to control the deformation of single floor basement pit near the shallow foundation building in soft ground, a new foundation pit supporting structure and control technology are developed and applied in the project. The passive pile is set in the foundation pit, and the transfer beam is set between the passive pile and the supporting pile. The monitoring of the horizontal displacement of the soil, the vertical displacement of the pit outside and the settlement of surrounding houses are carried out. The results show that with the excavation, the horizontal displacement curve of the deep soil body shows a "fish belly" shape, and the displacement of the soil in the excavation process and the demolition process is not much. The horizontal displacements of the deep soil, the vertical displacements of the pit and the settlements of the surrounding houses did not exceed the warning value. The deformation of the pit adjacent shallow foundation is effectively controlled by the application of the new supporting structure and control technology.

Case Analysis of Design and Construction of Deep Foundation Pit for Hospital Expansion Project in Complex Environment

Fu Ruiyong, Wu Denghui, Ye Shenglin, Zhao Qingliang, Ma Zhen

2020, 34(6): 339-343,361. doi: 10.3969/j.issn.1007-2993.2020.06.007

[Abstract](114) [PDF 2596KB](42)

Abstract:
Taking the construction project of Pediatric Comprehensive Building of Shandong Provincial Hospital as an example, the key technology in the design of deep foundation pit and the key control points in the construction process are discussed. The depth of the foundation pit is 15.7~19.9 m, and the surrounding conditions are complex. The newly built pediatric complex is only 3.2 m away from the 6-story pediatric ward building on the east side. Considering the site stratum and surrounding environment, pile-anchor structure is adopted in this foundation pit. The scheme of high-pressure jet grouting pile waterproof curtain combined with tube well dewatering is adopted in groundwater control. During the whole construction of the project, the foundation pit and surrounding buildings is monitored. The monitoring results show that the pile anchor support + high pressure jet grouting pile waterproof curtain + tube well dewatering scheme is economical and reasonable in this type of site, which ensures the safety of surrounding buildings. A reasonable process is adopted to minimize the impact on the medical conditions during the construction period.

Deformation Characteristics and Prevention Analysis of a Deep and Thick Fill Slope

Zhang Jian, Zhang Liwei

2020, 34(6): 344-348. doi: 10.3969/j.issn.1007-2993.2020.06.008

[Abstract](80) [PDF 27454KB](42)

Abstract:
A series of tensile cracks and lower fault cracks appeared in the buildings (structures) on the top of the slope in the survey area. Comprehensive survey methods are applied to find out the distribution of the fill, including geological survey, geological process analysis and slope structure analysis. Through the analysis of geological process, combined with the geological structure of the slope from the perspective of crack formation and evolution, the main factors of disease formation are analyzed. High and steep terrain, thicker fill, unfavorable stratum contact and continuous vehicle load are the main factors, and the slope is during the creep deformation stage. A three-dimensional geological model is established, and the stability of the deformation zone is evaluated through limit equilibrium method and numerical simulation. It is concluded that the unstable slopes of 1^# and 2^# are basically stable, and the 3^# unstable slope is during uneven settlement, which should be monitored more closely, and further treatment should be taken according to the monitoring results. According to the monitoring data of the past year, the slope deformation trend has slowed down, and all indicators are normal, which provides a basis for prevention suggestions.

Comprehensive Investigation on Risk Assessment and Hidden Danger of Ground Collapse in Shanghai

Fu Dong

2020, 34(6): 349-353. doi: 10.3969/j.issn.1007-2993.2020.06.009

[Abstract](107) [PDF 18461KB](20)

Abstract:
Based on the analysis of the risk and vulnerability of the occurrence factors of ground collapse in Shanghai, the risk grade division of ground collapse geological hazards in Shanghai is formed, and the risk distribution of ground collapse in Shanghai is evaluated, which provides the direction for further comprehensive investigation of the hazards. Under the guidance of the division, Jing'an District was selected as the demonstration area to investigate and monitor the potential ground collapse hazards. 20 potential hazards were found and early warning monitoring were carried out. Monitoring suggestions were given for key potential hazard areas such as North Tibet Road Zhongxing Road, Pushan Cross Road Pushan Road, Tianmu West Road Meiyuan Road, etc. Risk division provides basis for risk management policies of each risk level area. The methods of hidden danger inspection, geophysical exploration and monitoring provide technical support for the prevention and control of surface subsidence in Shanghai, and provide reference for the prevention and control of surface subsidence in other cities.

Brief Instroction of Fault Structure and Research on Seismic Parameter Adjustment of Rock and Soil in Shijiazhuang

Sun Lichuan, Yang Qiankun, Zhang Qian

2020, 34(6): 354-361. doi: 10.3969/j.issn.1007-2993.2020.06.010

[Abstract](81) [PDF 13644KB](14)

Abstract:
The characteristics of the main geological structures in the urban area of shijiazhuang were collated and compiled, and the activity of the faults was identified and graded according to the geotechnical engineering standards. According to the characteristics of stratigraphic distribution in Shijiazhuang, the effects of site classification and misclassified site classification on architectural structure design are discussed, as well as problems such as periodic adjustment of response spectrum characteristics, seismic acceleration adjustment, seismic grouping adjustment and fortification intensity adjustment, which are closely related to site classification.

Invasion Treatment of Retaining Pile in Foundation Pit Based on the Force Transmission and Addition Soil-nailing Method

Chang Qinghai, Zhao Mengmeng

2020, 34(6): 362-364. doi: 10.3969/j.issn.1007-2993.2020.06.011

[Abstract](52) [PDF 844KB](13)

Abstract:
In order to strengthen the reinforcement of retaining piles, the reasons of invasion and the treatment measures of retaining piles are analyzed and summarized by theoretical analysis method, and the force transfer method and the addition soil nail are introduced. The results show that the main reasons of invasion of retaining pile in foundation pit are divided into human factors and stratum factors. Through the combination method of force transmission and addition soil-nailing, the chiseled pile and adjacent pile can bear the overall force on the free surface in foundation pit, in a certain extent, the soil nails and mesh shotcrete panel of foundation pit could limit the unloading deformation of the side wall caused by excavation. The force transmission method and the addition soil-nailing method are proved feasibility, which can provide experience reference for similar projects.

Application of Cone Penetration Test for Soil Layers Division

Wang Gang, Jiang Wei, Chen Zongqing, Qin Shuangjie, Nie Liqi

2020, 34(6): 365-371. doi: 10.3969/j.issn.1007-2993.2020.06.012

[Abstract](172) [PDF 3022KB](50)

Abstract:
Soil layers division is a problem widely concerned in geotechnical engineering investigation. Aiming at solving this problem, drilling and standard penetration test (SPT) have been widely applied in engineering field, and abundant experience has been gained. Meanwhile, how to use cone penetration test (CPT) to solve the problem economically and effectively is of practical significance in engineering application. The application of static cone penetration curve in shallow soil layers division is studied based on the CPT curves acquired in a site located in south of Xuzhou, and the soil layers are divided by mechanics and named the soil by local experience. Comparing the soil layers division results acquired by this method and the results achieved by drilling hole, the division number of layers are the same. The depth of soil layers gained by this method is similar to that achieved by drilling hole when the soil is thick(the thickness is generally more than 1 m).For the interface depth of soil layers, the maximum and mean values of absolute error are 0.7 m and 0.24 m, and that of relative error are 0.54 and 0.16. From the comparison results, it is concluded that this synthesis method can reliably reveal the distribution of soil layers. Moreover, the features of the cone tip resistance-depth curves and the friction-resistance ratio-depth curves of four categories of soil layers were summarized, which offer a reference for soil layers division.

2020 Vol. 34, No. 6