岩土工程技术

Design and Application of Artificial Drilled and Expanding Bottom Perfusion CFG Piles in Composite Foundation

Cao Liang, Liu Huancun, Wang Yan

2014, 28(3): 109-112. doi: 10.3969/j.issn.1007-2993.2014.03.001

[Abstract](46) [PDF 687KB](8)

Abstract:
To construct a building in some special geological structure conditions, the key point of finishing the project successfully is how to choose the foundation type or the method of the foundation treatment. In this article, through a foundation treatment in Beijing which adopted artificial dig-hole and expanded bottom perfusion CFG pile in engineering practice, introduced design calculations, construction technology, reinforcement mechanism and scope of application of this kind of pile, to provide a useful reference for similar engineering design and construction of foundation treatment in Beijing.

Discussions of Soil Nail Stress Calculation Methods in Soil Nail Wall

Lu Feng, Yan Ronghua, Zhu Ming

2014, 28(3): 113-116,151. doi: 10.3969/j.issn.1007-2993.2014.03.002

[Abstract](33) [PDF 817KB](8)

Abstract:
A large number of full-scale model tests and field monitoring results show that soil nail internal forces have excavation effect. The maximum tension of soil nail appears in the middle of the foundation pit, the upper and lower internal forces are smaller. But the design and calculation theory of norms "Technical specification for retaining and protection of building foundation excavation" (JGJ 120——99) and "Specification for soil nailing in foundation excavation" all cannot accurately reflect the actual soil nail internal force we prototype observed at the scene. The above issues bring difficulty to reasonably determine the length of soil nail, make the calculation of internal forces and the length of soil nail rely more on experience, and lead to the design of soil nail forces unsafe or conservative. Here we analyzed the soil nail force calculated by current regulations is not consistent with the measured soil nail force, pointed out the defects existing in the current regulations calculation method, analyzed the effect of earthwork excavation of soil nail force, and discussed a simplified soil nail internal force calculation method based on incremental method.

Analysis of Stability in High Concentration Tailings Pond Upstream Embankment Method

Meng Tingwei, Wu Zhian

2014, 28(3): 117-120. doi: 10.3969/j.issn.1007-2993.2014.03.003

[Abstract](123) [PDF 825KB](8)

Abstract:
This text base on the method of Bishop, with analysis program XSTABL were used, the stability of the tailings dam under static conditions and seismic conditions were evaluated in this paper.

Comparative Analysis of Hyperbola Model Exponential Curve Model and Asaoka Model on Shan-jie Expressway

Li Lei, Yang Tao, Chen Shangrong

2014, 28(3): 121-125. doi: 10.3969/j.issn.1007-2993.2014.03.004

[Abstract](28) [PDF 930KB](6)

Abstract:
Estimation of the settlement in subgrade is one of the most critical problems in expressway. By the settlement measured data of shan-jie expressway, the paper research the common method in the estimation of settlement, such as hyperbola model exponential curve model and Asaoka model. The results show that hyperbola model and Asaoka model are more consistent with the measured data,applicable estimation of the settlement in shanjie expressway. The main factors which affect the accuracy of hyperbola model and Asaoka model were analyzed. How to improve its predictive accuracy was clear.

Application and Analysis of Inclinometer in Monitoring Landslide Deformation

Chen Daikun, Qiao He

2014, 28(3): 126-130. doi: 10.3969/j.issn.1007-2993.2014.03.005

[Abstract](42) [PDF 1518KB](6)

Abstract:
First, this paper briefly introduces construction and principle of the inclinometer, analyzes the main factors which cause inclinometer produce deviation. Then, take landslide monitoring project in Huale as an example explain application of inclinometer in monitoring landslide project. Though monitoring the five key points distributed in different locations and gathering all monitoring-data half month as a period, handle monitoring-data to get depth-displacement bight followed with time of each monitor point so that we can comparatively and clearly master situation of landslides in each interval short time. Finally, we can provide important basis and objective advice for administer landslide through analyze the change regulation of depth-displacement bight.

Characteristics of New Low Elastic Modulus Concrete

Zhang Yuting, Zuo Dianjun, Chen Wenliang

2014, 28(3): 131-136. doi: 10.3969/j.issn.1007-2993.2014.03.006

[Abstract](39) [PDF 807KB](4)

Abstract:
For its excellent performance and mechanical properties, low elastic modulus polypropylene fiber concrete has became one of the materials used in the main cut-off wall of water conservancy projects in recent years. Based on laboratory tests, low elastic modulus for polypropylene concrete strength, slump characteristics were studied; a set of concrete durability permeate collection instrument for polypropylene low elastic modulus of concrete was developed, and permeability and durability were studied. The test results showed that., compared with the traditional low elastic modulus of concrete, compressive strength and elastic modulus of polypmpylene low elastic modulus of concrete changed little, but with higher tensile strength, lower permeability and longer durability. These findings of polypropylene low elastic modulus of concrete will provide technical supports for application of cut-off wall darn engineering.

Optimization and Analysis of the Method to Determine Kaiser Point of the Method to Measurement to Stress by Acoustic Emission

Ni Chunbo, Zhang Guangqing, Jia Jiubo

2014, 28(3): 137-142. doi: 10.3969/j.issn.1007-2993.2014.03.007

[Abstract](97) [PDF 808KB](20)

Abstract:
The key of the study of acoustic emission measurement of in-situ stresses is to properly determine the Kaiser point. Through the simulation of core concrete in uniaxial compression failure process of acoustic emission test, the stress-strain curve,the relationships between stress, intensity and cumulant of acoustic emission with time of the specimens in the test process are obtained. The specimens are analyzed respectively with mutation point, maximum curvature method, double tangent method,again loading method (incomplete erasion phenomenon, two loading phase subtraction) various comprehensive judgement method and statistical analysis method of acoustic emission signal intensity. Understands the characteristics of Kaiser point of the specimens, summarizes and analyzes the methods to determine the Kaiser point and their adaptability, and was optimized. Research shows that the test can determine the sample physical properties,various methods can explain the phenomenon of Kaiser point from different angle, various comprehensive analysis will be more comprehensive to determine Kaiser point.

Deformation Monitoring and Numerical Analysis of Supporting Structure of Open Ring Deep Foundation Pit

Zhang Xin, Zhao Shengfeng, Huang Guanglong

2014, 28(3): 143-147. doi: 10.3969/j.issn.1007-2993.2014.03.008

[Abstract](35) [PDF 1385KB](8)

Abstract:
There are thicker soft soil layers distributed in the subsoil of Nanjing Yangzi coal storage silo project which deep foundation engineering excavates a pit with the depth of 11.40 m. The row piles were used as retaining structure with cast-in-situ bored pile and ring beams as struts which are 10. 0 m length of open arc. However, the open sections of ring struts have a great influence on the deformation and stability of foundation pit excavation. Based on this practical engineering, a three-dimensional finite element numerical analysis model was established and the soil and the interface elements were modeled as elasto-plastic materials obeying Mohr-Coulomb failure criterion, then staged excavations were simulated and calculated. Compared with monitoring data, the results showed that the difference between calculated values and measured values was negligible, and the variation trend was almost the same. The calculated results of finite element are reliable, which can be references for design and construction improvement of similar engineering.

Study of Soft Soil Deep Excavation Case by the River

Wang Ningwei, Han Xu, Zhu Feng

2014, 28(3): 148-151. doi: 10.3969/j.issn.1007-2993.2014.03.009

[Abstract](30) [PDF 895KB](8)

Abstract:
To the Dandong deep foundation pit engineering background, difficulties in the area of soft soil foundation pit are analyzed. This paper introduces the causes of secant pile using the Dandong Aqua City support engineering,and explain the advantages, bored pile construction process, and the displacement monitoring data of field analysis secant pile supporting effect.

Study on Support Design and Monitoring of Deep Foundation Pit in Suzhou Performing Arts Center Phase Ⅱ

Fan Qinjian, Tao Zhu, Song Dexin

2014, 28(3): 152-156. doi: 10.3969/j.issn.1007-2993.2014.03.010

[Abstract](30) [PDF 1015KB](11)

Abstract:
During excavation of deep foundation pit, the bored piles combined with concrete struts have a positive role in retaining soil, while double waterproof curtain formed by cement-soil mixing piles and dense-compacted grouting can effectively cut off water. Based on the project of Suzhou performing arts center phase Ⅱ, measured datas in the process of excavation are given. Then the deformation of retaining structure, change of underground water, settlement of surrounding buildings are also analyzed and studied to verify design and construction projects of support structure and waterproof curtain of this example. The results show that these measures achieve good implementation. It could provide references and suggestions for similar foundation pit projects in Suzhou area.

Application and Numerical Simulation of Retaining Structure with Double-row Piles

Zhang Dan, Fa Liteng, Chen Quanfei

2014, 28(3): 157-159. doi: 10.3969/j.issn.1007-2993.2014.03.011

[Abstract](23) [PDF 1741KB](10)

Abstract:
Retaining structure with double-row piles has better lateral stiffness and ability of limiting the deformation. In this paper we took a foundation pit in Chaoyang District of Beijing as an example to introduce the applicability of retaining structure with double-row piles in the complex environment conditions. In addition,we conducted discussions on the retaining structure's deformation characteristics with double-row piles by project actual measurement and laboratory simulation.

Application of Soil Nailing of Steel Tube Combined with Compaction Grouting in Foundation Pit with Deep Miscellaneous Fill

Wang Tao, Yan Zhenhuan

2014, 28(3): 160-163. doi: 10.3969/j.issn.1007-2993.2014.03.012

[Abstract](37) [PDF 647KB](10)

Abstract:
Based on engineering example, a supporting method is introduced of soil nailing of steel tube combined with compaction grouting in foundation pit with deep miscellaneous fill. The design and construction of soil nailing of steel tube and compaction grouting is detailed described. The monitoring results show that the supporting method can effectively control the deformation of foundation pit, ensure the safety of foundation pit and underground structures. And it provides a reference for the similar condition of foundation pit.

2014 Vol. 28, No. 3