岩土工程技术

An Improved Expression of Safety Factor for Soil Slope

Lei Shengyou, Hui Huiqing, Chen Lianguo

2020, 34(4): 187-190. doi: 10.3969/j.issn.1007-2993.2020.04.001

[Abstract](79) [PDF 829KB](17)

Abstract:
Based on the shear strength of cohesive soil, the shear strength expression of soil divided by the safety factor is incontradiction with the Coulomb criterion. Only the frictional resistance of the shear strength expression is reduced in the improved expression, thus constructing a new strength reduction formula for cohesive soil which conforms to the Coulomb criterion. In this way, a new slope stability factor expression is derived. Then the expression is used to calculate the safety factors of seventeen soil slopes. The results show that the values of safety factor of soil slopes calculated with the new expression are 0.22%~25.05% smaller than those in the current textbooks, which is safer for engineering projects. In comparison,the proposed new safety factor expression of soil slope is more reasonable. This improved expression has reference value for related engineering analysis.

Soil Pressure Measuring Pipe Based on BOTDR

Li Chao, Xiao Jingze, Liu Yu, He Jing, Zhou Yuanxin

2020, 34(4): 191-195. doi: 10.3969/j.issn.1007-2993.2020.04.002

[Abstract](90) [PDF 1605KB](9)

Abstract:
At present, the vibrating wire soil pressure gauge and the resistance-type soil pressure gauge are widely used. However, there are some disadvantages, such as high cost, poor anti electromagnetic interference and low survival rate of the instrument. Moreover, the test data are easy to be distorted and it is difficult to accurately measure the soil pressure. Based on BOTDR, a soil pressure pipe for soil pressure monitoring is designed. The structural characteristics and measuring principle of the soil pressure pipe are introduced, and its pressure and temperature calibration tests are carried out. In the outdoor field, the pressure pipe is buried 25 m underground by the method of drilling directly, and the field measurement is carried out to obtain the data. The comparison with the data of vibrating wire soil pressure gauge and the calculated value shows that the method is effective.

Geological Disaster Model of Loess Collapse in Ji County, Shanxi Province

Li Yuzhu, Li Jie

2020, 34(4): 196-200. doi: 10.3969/j.issn.1007-2993.2020.04.003

[Abstract](53) [PDF 1674KB](15)

Abstract:
Loess collapse is the main geological disaster in Ji County, Shanxi Province. Collapse is a process of partially creep—mostly progressive failure—abrupt instability.Based on the analysis of the main controlling factors of the loess collapse, 6 collapse models are summarized, including saturated slope spalling type, freezing-thawing collapse type, plant root splitting collapse type, joint cutting collapse type, unstable rock (soil) collapse type, slope shear failure collapse type. The analysis of the evolution and the disaster model of collapse has reference significance for disaster prevention and reduction.

Treatment Measures of Metro Shield Tunnel in Red Clay Karst Area

Zhang Meicong

2020, 34(4): 201-205. doi: 10.3969/j.issn.1007-2993.2020.04.004

[Abstract](84) [PDF 10377KB](13)

Abstract:
Soft plastic red clay covers the limestone. The change of surrounding environment easily leads to the connection and flow between red clay and karst cave, which could result in karst geological disasters such as ground subsidence, and brings serious safety risks to the construction and operation of metro tunnels as well as the surrounding environment. Taking the Dahualing Station to Jiangxiaketing Station of Zhifang Line (Line 27) of Wuhan Metro as an example, the distribution and development characteristics of red clay and karst are summarized in combination with special karst investigation. On this basis, the treatment measures of red clay and karst are put forward. Practice proves that these measures ensure the construction safety and operation safety of metro shield tunnel, and achieve the expected results, which could be reference in similar projects.

Study on Survey Technology of Large-scale Pit Filling in Road Engineering

Cheng Hailu, Han Zekun, Wang Tao, Lu Pengyu

2020, 34(4): 206-210,224. doi: 10.3969/j.issn.1007-2993.2020.04.005

[Abstract](57) [PDF 4265KB](20)

Abstract:
Taking the road engineering of Meishikou Road as an example, the large-scale earth filling pits were classified according to the composition and scale of the earth filling, and the types of soil filling were classified according to their origin and composition. Meanwhile, domestic garbage was divided into incinerated garbage and unincinerated garbage. Through a variety of means, in view of the different filling, research and comparative analysis on several foundation treatment methods are conducted, a more perfect filling holes survey and processing system is provided.

Robust Design Approach of Gravity Retaining Wall Based on Info-Gap Theory

Cui Yajun, Wang Fajun, He Peng, Zheng Chengcheng, Wang Fengju

2020, 34(4): 211-216. doi: 10.3969/j.issn.1007-2993.2020.04.006

[Abstract](55) [PDF 1207KB](9)

Abstract:
Due to the variability of geomechanical parameters and the limit of the obtained data information, the existing uncertainty analysis method for the stability of gravity retaining wall is difficult to reflect the true safety performance and failure level. The Information-Gap theory (Info-Gap) is introduced to the existing analysis method for the stability of retaining wall. Firstly, based on the analysis about the allowable change range of these uncertain variables and its measure method, a robust reliability evaluation model for uncertainty analysis of stability about gravity retaining wall is established. Secondly, based on the response output model to the stabilization and security function of gravity retaining wall, the robust reliability index is obtained by interval combination algorithm. Consequently, the robust design approach of gravity retaining wall is established based on Info-Gap theory. To demonstrate the effectiveness and significance of the proposed robust design methodology, an illustrative example is followed. A comparative study was made of the design on the basis of the robust design methodology and reliability-based design methodology. The proposed methodology affords a novel approach for the reliability assessment of retaining wall when the uncertain information is unavailable or scarce.

Monitoring and Tracking Analysis of Underwater Topography in Yangshan Deepwater Port

Zhou Mi

2020, 34(4): 217-221. doi: 10.3969/j.issn.1007-2993.2020.04.007

[Abstract](57) [PDF 1902KB](10)

Abstract:
In order to measure the depth of water and ensure the safety of navigation, dual-frequency GNSS receiver with dual-frequency depth sounder were used. GNSS RTK technology and navigation sounding software are used to collect plane and depth data. Underwater topographic monitoring and tracking analysis of Artificial Maintenance Section and Harbour Waters were carried out in Yangshan Deepwater Port. All records, calculations and accuracy indicators meet the requirements of the standards, and the measurement results arereliable. The current situation of waterway, the tendency of water depth and the river bed changing are obtained, which provides a preliminary reference for dredging. The safety for the normal navigation of Yangshan Deepwater Port is guaranteed.

Browser Development for Information Entry of Ancient Tree Based on ObjectARX

Chen Zhen, Yin Yanyun, Ma Hongyu, Li Shifeng, Du Wenxiao

2020, 34(4): 222-224. doi: 10.3969/j.issn.1007-2993.2020.04.008

[Abstract](44) [PDF 770KB](9)

Abstract:
The advantages and disadvantages of several secondary development methods of AutoCAD platform are compared, and ObjectARX 2018 based on C ++ language is selected to realize the input and browse of attribute informations for ancient trees in AutoCAD 2018. The attribute informations of ancient trees could be input by users through human-computer interaction, and the informations are stored in the extended attribute XData of the graph.Add a reactor to AutoCAD to obtain the drawing object of mouse position and its XData, and then the attribute informations are displayed in the Tooltip. The logic structure of the program is introduced, and the key codes are provided, which could be used as a reference for similar functions.

Cause Analysis and Treatment Measures of Abnormal Bearing Capacity of Pile Foundation in a Project

Peng Manhua, Chen Zhixin, Zhang Haishun

2020, 34(4): 225-228,233. doi: 10.3969/j.issn.1007-2993.2020.04.009

[Abstract](61) [PDF 1070KB](34)

Abstract:
Two pile bearing capacity tests have been carried out in a project, but the bearing capacity of test piles does not meet the design requirements. The geological factors and construction factors are analyzed, and the corresponding treatment measures are provided considering the aspects of construction technology and grouting technology on the basis of eliminating geological factors. Relevant measures are taken, and the bearing capacity of the third pile test construction can finally meet the design requirements. These measures have important guiding significance for the construction of large-area engineering piles, and also have important reference significance for the construction of post-grouting bored piles in similar thick sandy soil and silty soil.

Application and Prospect of Integrative Geophysical Exploration in Urban Water Engineering

Gu Xiaoshuang

2020, 34(4): 229-233. doi: 10.3969/j.issn.1007-2993.2020.04.010

[Abstract](52) [PDF 13193KB](19)

Abstract:
With the continuous progress of science and technology and the advent of the age of intelligence, the proportion of urban water engineering planning and construction is increasing. Focusing on the water conservancy project under the complex urban environment, the integrative geophysical method is used to detect the underground pipelines and underground obstacles, which makes up for the defects and deficiencies of the traditional detection methods. Specific solutions and measures are provided, which has achieved good results in practical application. This research has practical significance in the optimal layout of water engineering lines, economic rationality of design scheme and safe construction.

Design and Implementation of Digital Management System for Historic Building Protection Based on SuperMap

Li Shifeng, Yin Yanyun, Du Wenxiao, Chen Zhen, Shao Pan

2020, 34(4): 234-237. doi: 10.3969/j.issn.1007-2993.2020.04.011

[Abstract](91) [PDF 1678KB](15)

Abstract:
The digitization of historic buildings has become an important development direction of cultural relics protection and has placed an urgent need on the construction of management system for historic buildings protection. According to the actual needs of historic buildings protection management, combining with the 2D and 3D WebGIS technology, a management system are designed and implemented. This system consists of seven subsystems, including basic management, archive management, 3D management, deformation data management, cultural protection propaganda, statistical inquiry and system management. This management system could basically realize the display, release and management of historic buildings on the 2D and 3D geographic information platform, and provides data support for the protection decision.

Experimental Study on Leaching of SP-MOC Solidified Arsenic-contaminated Soil

Zhang Qinxi, Zhang Xuedong, Zhang Zhihong, Jiang Yuxiao

2020, 34(4): 238-242. doi: 10.3969/j.issn.1007-2993.2020.04.012

[Abstract](58) [PDF 1302KB](9)

Abstract:
To determine the optimum ratio of arsenic-contaminated soil with different concentrations, SP-MOC curing of arsenic-contaminated soil and toxicity leaching test are carried out in the relocation of a chemical plant in Jiangsu Province. The change law of moisture content, pH value and leaching concentration of solidified body under different curing agent ratios are investigated, and the effect of curing age on leaching concentration is analyzed. The results show that the moisture content of the solidified body is negatively correlated with the curing age, and the pH value of the solidified body increases with the increase of the curing agent content, reaching the maximum pH value when the curing age is 14 days. With the increase of arsenic pollution concentration, the ratio of needed curing agent increases. When the background value of arsenic is 90 mg/kg, 188 mg/kg, 275 mg/kg, and 339 mg/kg, the curing agent ratios satisfying the leaching limit are 3%, 5%, 8%, and 8%, respectively. The leaching concentration decreases first and then increases slightly with the increase of curing agent content. When the content of curing agent is 8%, the leaching concentration reaches the minimum. The leaching concentration decreases with the increase of curing age, and reaches the minimum after 14 days of curing.

Experimental Study on Bearing Characteristics of Post Grouting for Underwater Cast-in-pace Bored Piles

Liu Huancun, Sun Fengling, Liu Tao

2020, 34(4): 243-249. doi: 10.3969/j.issn.1007-2993.2020.04.013

[Abstract](74) [PDF 2043KB](24)

Abstract:
The experiment of post grouting for underwater cast-in-pace bored piles has been constructed based on a large industrial construction project located in the East and West Lake area in Wuhan. Underwater cast-in-pace bored piles is adopted in the foundation design. For different pile diameters, different pile lengths at the same bearing layer of pile tip, the respective experiment of the bearing capacity of single pile is tested by post grouting and non-grouting. By the internal force test of pile body, the distribution law of pile side resistance and pile tip resistance with the increase of the pile top load under different working conditions are revealed, and the pile tip and pile side load sharing ratios are also obtained, which provides reference for the further design and construction of the pile foundation.

2020 Vol. 34, No. 4