岩土工程技术

Research Status and Development of Salt and Frost Heaving Theory Insulfate Saline soil

Wang Jinghui, Zhang Weibing

2019, 33(4): 187-191,249. doi: 10.3969/j.issn.1007-2993.2019.04.001

[Abstract](74) [PDF 1196KB](11)

Abstract:
The salt and frost heaving damage of soil in the saline soil area seriously endangers the stability and durability of pipelines,highways,railways,airport runways,bridges and other engineering buildings.Therefore,it is very important meaning to solve the problems of salt and frost heaving in actual engineering.In this paper,the latest research results on the mechanism of salt frost heaving in recent years are reviewed from the aspects of microstructure,single cooling,freeze-thaw cycle,water-salt migration and construction mechanism model.The problems and shortcomings in the current research are summarized,and the research direction of salt freezing and swelling mechanism of saline soil is prospected.

Hydro-geological Conditions in Yanqing Plain Area

Li Jie, Ma Bingwu, Zhang Xueyang

2019, 33(4): 192-196. doi: 10.3969/j.issn.1007-2993.2019.04.002

[Abstract](86) [PDF 5161KB](15)

Abstract:
In recent years,with the planning and construction of World Horticultural Exposition Venues,Winter Olympic Venues,Yanqing New Town and Zhongguancun Yanqing high-tech Park,more and more projects will be constructed in the Yanqing Plain Area.During the whole evolution of the Quaternary,the strata in Yanqing area uplifted rapidly and frequently than the Beijing Plain Area,Comparatively,the sedimentary laws are more complex.The main rivers in the area(Gubadaling River and Guguishui River)had experienced reversal of flow direction.As a result,the topographic conditions and groundwater conditions in the study area are complex,the hydro-geological conditions are quite different from those in the adjacent Beijing.The complex hydro-geological conditions have a great impact on the construction of the project in this area.By collecting the relevant engineering geology and hydro-geology background information of the investigation area and combining the groundwater monitoring information of our company in the Yanqing area,the author investigates and studies the hydro-geology conditions of the Yanqing area,and divides the hydro-geology conditions of the area into some hydro-geological zones,so as to guide the relevant engineering construction.

Effects of Surface Subsidence in Excavation of Metro Crossing Passage Tunnel by Shield Machine

Sun Longfei, Chen Zhenlei, Li Jiancheng

2019, 33(4): 197-201,213. doi: 10.3969/j.issn.1007-2993.2019.04.003

[Abstract](57) [PDF 1898KB](12)

Abstract:
The excavation of the metro crossing passage tunnel by the shield method is turned into reality at the Ningbo metro subway tunnel,that is the world first metro crossing passage.However,for the effects of the excavation by the shield machine on the surface subsidence,rare studies can be found and the deep understanding of the mechanism is needed.Taking the excavation of the metro crossing passage tunnel in a certain section of the Ningbo Metro Line 3 as an example,this paper conducts the field test and CAE(Computer Aided Engineering)simulation on the construction process of the shield method.The calibration analysis between test data and CAE results of the surface subsidence during the construction process is performed.The variation law of the subsidence amplitude under various working conditions is obtained,and the dangerous conditions that need to be paid attention to during the construction of the metro crossing passage tunnel by the shield machine are pointed out.Consequently,an authentic,reliable and advanced simulation process is established,and thus the surface subsidence caused by the metro crossing passage tunnel and other similar constructions can be well monitored and predicted.

Stability Evaluation of Large and Gently-inclined Goaf

Tang Heming

2019, 33(4): 202-207,217. doi: 10.3969/j.issn.1007-2993.2019.04.004

[Abstract](60) [PDF 1479KB](11)

Abstract:
As there are plenty of factors affecting the stability in the mined-out area and in order to better evaluate the stability of large and gently-inclined mined-out area,this paper numerically simulated the multiple mining conditions with FLAC 3D finite difference software and proposed major factors affecting the stability in the mined-out area of such type,and then weighed each influencing factor with analytic hierarchy process(AHP)on this basis.On the goal stability of many coal mines in Zhongyang County of Shanxi Province,we scored the each influencing factor according to the Comprehensive Scoring Table of Influencing Factors,and finally computed the total score of the stability in the mined-out area and comprehensively determined the grade of stability in the mined-out area thereby.Results from this method for stability evaluation are consistent with those from the observational method for the ground movement deformation in goaf,therefore,the results are of great referential significance to evaluate the stability in similar mined-out areas.

Optimization Design of Deep Foundation Pit in Complex environment

Zhang Dan, Chen Quanfei, Xia Xiangdong, Gang Yuyin

2019, 33(4): 208-213. doi: 10.3969/j.issn.1007-2993.2019.04.005

[Abstract](90) [PDF 1995KB](23)

Abstract:
At present,urban space is becoming increasingly scarce,and the narrow space and complex environment problems faced by excavation of foundation pits in cities have gradually become the key and difficult points in the design of foundation pits.At the same time,most of the foundation pits are excavated in deeper depth under the idea that the whole engineering design is to underground space.Based on the design case of a foundation pit project in Changping District of Beijing,this paper introduces the optimal design of foundation pit in complex environment.The foundation pit is adjacent to the surrounding buildings,and the foundation depth,foundation form,construction age and use function of the surrounding buildings are different.According to the environmental conditions,the pile-anchor supporting system of “multi-elevation+step reduction+different parameters” is designed and adopted,and the dynamic implementation is also carried out in the construction process.Design and management,support structure technology is simple,cost-saving,dynamic and flexible,while ensuring the safety of foundation pit engineering,which can be used for reference for similar projects.

Improving Geotechnical Investigation Quality for Karst Areas

Cheng Yu, Long Ju, Zhang Lin

2019, 33(4): 214-217. doi: 10.3969/j.issn.1007-2993.2019.04.006

[Abstract](92) [PDF 819KB](23)

Abstract:
Geotechnical investigation lays the groundwork for engineering design and construction.Owing to the complicated geological conditions in karst areas,to ascertain the distribution of karst landform is difficulty by geotechnical investigation in these areas.In karst areas work quality of geotechnical investigation is dependent on the skill level of investigation personnel,the quality of field work,the effectiveness of investigation techniques and the sense of responsibility committed for foundation subsoil inspection.

Sleeve Valve Pipe Grouting in Artificial Filling Tunnel

Xia Xiangdong, Zhang Dan

2019, 33(4): 218-221. doi: 10.3969/j.issn.1007-2993.2019.04.007

[Abstract](46) [PDF 994KB](15)

Abstract:
In a subsurface excavation section of the flood diversion culvert of Fushi Road,the large part of the shallow culvert subsurface excavation is in the artificial fill,and the thickness of the artificial fill at the bottom of some areas is still 2 m.Artificial filling is loose,poor self-stability,easy to collapse,not easy to form holes,and difficult to construct.In order to avoid potential safety hazards caused by artificial filling and reduce tunnel deformation in the later stage of construction,sleeve valve tube grouting technology is used to reinforce the filling layer to ensure the safety of construction and the quality of tunnel engineering.According to the effect of project implementation,sleeve valve pipe grouting reinforcement has better effect on settlement and deformation control of excavation of tunnel in artificial fill.

3D Laser Scanning Technology and BIM Technology in Ancient Building Protection Surveying and Mapping

Ma Hongyu, Zhao Xin

2019, 33(4): 222-225. doi: 10.3969/j.issn.1007-2993.2019.04.008

[Abstract](220) [PDF 5694KB](22)

Abstract:
An example of cultural relics construction project in Gubeikou Village,Miyun District,Beijing is introduced.The 3D laser scanning technology and BIM technology is applicated in ancient building surveying and mapping.The advantages are proved in mapping and cultural relic protection by comparing traditional mapping methods.

Sliding Micrometer in Pile Foundation of Super High-rise Building in Loess Area

Peng Wei, Lou Yunlei

2019, 33(4): 226-230. doi: 10.3969/j.issn.1007-2993.2019.04.009

[Abstract](50) [PDF 2834KB](11)

Abstract:
A large number of super high-rise buildings have been built in northwest China in recent years because of the developing of the “One Belt and One Road”.During the construction of such buildings,engineers are paying more and more attention on the internal force condition of pile.In comparison with the traditional test method for pile internal force,the technique of sliding micrometer has obvious advantages.Based on a case study in which the application effectiveness of the sliding micrometer technology was evaluated in the construction of pile foundation for super high-rise buildings,this paper provide key data on post-grouting pile construction technology,bearing capacity and its distribution characteristics so as to deepen the understanding of loess engineering characteristics and provide guideline and reference for similar projects in future.

Tensioning Squence of Bolt to Prestress in Pile-Anchor Support

Chen Quanfei, Zhao Jiewei, Guo Lanjie

2019, 33(4): 231-235. doi: 10.3969/j.issn.1007-2993.2019.04.010

[Abstract](68) [PDF 1532KB](11)

Abstract:
Based on the deep foundation pit support project in Beijing,combined with measured data of prestressed bolt in pile-anchor support system,this paper comprehensively analyzed the regular pattern with time by the different tensioning sequence of bolt.Under the same conditions,it is considered that the prestress loss rate of the anchor is the smallest in the adjacent tensioning sequence

Working Mechanism and Characteristics of Tension Dispersion Type Soil Anchor

Zhao Xiaofeng

2019, 33(4): 236-239. doi: 10.3969/j.issn.1007-2993.2019.04.011

[Abstract](39) [PDF 771KB](13)

Abstract:
In this paper,the critical anchorage length of soil anchors and its determination methods are analyzed by means of simplified theoretical calculation and calculating the outburst bearing capacity with the in-situ drawing test of anchor cable.It is proposed that the tensioned dispersion anchor is a simple and easy method to solve the problem of ultimate anchorage segment length in soil anchor.It also analyzed and explained the working mechanism and trait of the tensioned soil.

Test and Analysis of Dynamic Characteristics of Coral Reef Foundation in Indian Ocean

Zou Guigao, Wang Duli, Wang Yipeng

2019, 33(4): 240-244. doi: 10.3969/j.issn.1007-2993.2019.04.012

[Abstract](45) [PDF 2160KB](8)

Abstract:
Based on the runway construction project of the Maldives Velana International Airport in the Indian Ocean island country,the dynamic characteristics of the coral reef dredger fill foundation are tested,and the vibration characteristics of the coral sand foundation are revealed,It provides basic information for the selection of the runway foundation treatment methods.

Reinforcement on Soil Settlement Under Confined Conditions

Fu Zhibin, Liu Zhihua, Jie Yuxin

2019, 33(4): 245-249. doi: 10.3969/j.issn.1007-2993.2019.04.013

[Abstract](35) [PDF 1402KB](7)

Abstract:
Centrifugal model tests were conducted to investigate the influence of the reinforcement on soil settlement under confined conditions.Three tests were carried out.One has no reinforcement,the other two were reinforced with reinforcement(vertical)spacing of 5 cm and 3cm,respectively.The settlements of typical points ware recorded during the test.Results shows that settlements of the typical point increase with the increase of acceleration.The soil settlements without reinforcement,with 5cm spacing reinforcement and 3cm spacing reinforcement successively reduce,indicating that under confined conditions the reinforcement can still decrease the soil settlement.The smaller the reinforcement spacing,the better effect it can bring.The reason may likely lie in the facts that the soil displacement is uneven during the process of deformation.The study is helpful to understand comprehensively the mechanism of reinforced soil.

2019 Vol. 33, No. 4