2019 Vol. 33, No. 2

column
  Previous Issue | Next Issue 
Display Method:
Technology Development and Exploration
Study of Treatment Scheme of Deep Collapsible Loess Foundation in Ningxia
Han Zigang, Zhang Gangzhu
2019, 33(2): 63-65,88. doi: 10.3969/j.issn.1007-2993.2019.02.001
[Abstract](58) [PDF 803KB](14)
Abstract:
In the southern part of Ningxia,the thickness of collapsible loess is large,the collapsibility coefficient is large,but the compression index is poor.Correspondingly,the foundation treatment is difficult and costly.Especially,it is most prominent of the contradiction between the safety and economy of the low-rise buildings foundation in this area.It becomes a major obstacle to the development of the region.Aiming at this problem,a comprehensive treatment plan is adopted to partially eliminate collapsibility by adopting cushion method,and stricted waterproof measures and structural measures are taken at the same time.Stricted the results show that the comprehensive treatment plan is scientific,safe,economical and applicable,the engineering practice that used this foundation treatment scheme in this area has proved that this scheme can well solve the huge contradiction between safety and economy in the foundation treatment of low-rise buildings in the area,and take the both achieve harmonization.
Construction Technology for Bored Piles of Cable-stayed Bridge Tower in Karst Area
Cai Xiaonan, Zhang Wenyuan, Wang Yudong
2019, 33(2): 66-69. doi: 10.3969/j.issn.1007-2993.2019.02.002
[Abstract](73) [PDF 1642KB](7)
Abstract:
The No.22 tower of the Yangmeizhou Bridge locates in Land-water Interface with many karst caves.This paper attempts to propose key points of construction for bored piles in such complicate conditions to guarantee the safety,economy and high efficiency.The main research contents include building a composite steel tube pile cofferdam as a constrcution platform,optimizing the execution order of group of piles in the cofferdam,and improving the construction technology for bored piles in the karst area.Such study can provide significant suggestions and references for similar engineering constructions.
Subway Investigation Parameters Analysis and Determination of Cretaceous Strata in Changchun District
Guo Hongmei
2019, 33(2): 70-74. doi: 10.3969/j.issn.1007-2993.2019.02.003
[Abstract](49) [PDF 779KB](11)
Abstract:
Cretaceous conglomerate and mudstone universally exist in Changchun district,but conglomerate is difficult for sample drilling to do laboratory tests; mudstone is affected by many factors such as water stability,expansibility and slaking; many parameters,such as bearing capacity value,shear test parameter,permeability coefficient and coefficient of subgrade reaction,confirm mainly by empirical data evaluation method,There has a big difference on parameter rationality and accuracy.The article proposed bearing capacity values,shear strength,parameters,permeability and in-situ coefficient of subgrade reaction and so on by in-situ plate loading test,water immersion loading test and in-situ shear test on mudstone and conglomerate of cretaceous strata in Changchun district,,providing a geological reference for subway design and construction.
Inferring Method of Coral Sand Coefficient of Secondary Compression Based on Settlement Comparison of Vibration Rolling
Wang Duli, Xiao Guohua, Li Xing, Sun Lanning
2019, 33(2): 75-78. doi: 10.3969/j.issn.1007-2993.2019.02.004
[Abstract](49) [PDF 1306KB](6)
Abstract:
The engineering has great practical significance for the prediction of post-construction settlement,and the secondary compression coefficient is the key parameter for the prediction of post-construction settlement.It is a difficult problem to determine the second compression coefficient of dredged coral sand by laboratory tests with undisturbed soil samples.In this paper,a method is presented for estimating the secondary compression coefficient of coral sand based on the comparison and inversion of the subsidence of vibratory compaction and a calculation example is given.The method infers the secondary compression coefficient of coral sand by inquiring the historical filling time of the old dredger filling site,comparing the surface settlement of the new dredger filling test area and the old dredger filling test area in the course of the ground treatment test of vibratory compaction.At the same time,the factors are analyzed of affecting the inversion results.
Application of FLAC3D Under Complex Engineering Conditions
Cui Liang, Li Lianying, Ma Lemin
2019, 33(2): 79-83. doi: 10.3969/j.issn.1007-2993.2019.02.005
[Abstract](73) [PDF 2965KB](16)
Abstract:
The use of construction waste is a new direction to build mountains and landscapes for modern cities.However the large area of the mountainous project and the largely load,a series of engineering geological problems are often generated.This problem is more prominent in soft soil areas.In order to make the mountain stacking work smoothly,the foundation must be processed to a certain extent,while the conventional calculation can only select the typical section or section for local analysis,and can not reflect the real three-dimensional influence characteristics,but numerical analysis can effectively solve this problem.In this paper,the finite difference software FLAC3D is used to analyze a certain mountainous project in Tianjin,which provides a strong basis for optimizing the ground treatment plan.
Common Engineering Problems and Treatment Methods for Backfilling Soil in Foundation Trench
Wang Yingjun, Huang Changqian
2019, 33(2): 84-88. doi: 10.3969/j.issn.1007-2993.2019.02.006
[Abstract](152) [PDF 823KB](17)
Abstract:
The common engineering problems caused by the poor quality of the backfill soil are summarized and analyzed in the foundation trench,as well as several main reasons that are difficult to be compacted are proposed for the backfill soil in the foundation trench,and then put forward various treatment methods of backfill soil in the foundation trench and their main applicable conditions.
Influence Analysis of “Rockfill Layer” on Construction and Main Points of Engineering Investigation
Li Xinyuan
2019, 33(2): 89-91,96. doi: 10.3969/j.issn.1007-2993.2019.02.007
[Abstract](39) [PDF 720KB](11)
Abstract:
Rockfill belongs to the “special molecule” of the soil-filling,it has a great influence on investment,design and construction of enginees projects。Fully understanding the “harmfulness”,economic、reasonable and targeted design and construction measures can achieve the effect of avoiding design change,saving time and controlling cost。Engineering investigation is the most important basic work,whether the data is accurate or not,It can directly lead to different results。Through the practical engineering experience,this paper analyzes the influence of the rockfill layer on the construction of the project,and clarifies that the engineering investigation work should not only meet the requirements of the relevant standards,but also should pay attention to the key points and adopt measures,which can be reference in engineering investigation,design and construction。
Consolidation Settlement Analysis of Reclaimed Soil Foundation Reinforced by Directly Vacuum Preloading Method
Sun Jiarui, Wang Changming, Wu Changjiang
2019, 33(2): 92-96. doi: 10.3969/j.issn.1007-2993.2019.02.008
[Abstract](46) [PDF 1074KB](8)
Abstract:
The directly vacuum preloading method can shorten the construction period and has obvious effects.It is a soft ground treatment method widely used in coastal areas of China in recent years.In addition to theoretical analysis,realtime monitoring data of settlement,pore water pressure and other indicators are often used as the basis for judging the degree of foundation consolidation in the process of foundation treatment.In this paper,the consolidation degree of the foundation is analyzed by the project of blow-filled soil consolidation in hangzhou bay area.The result shows that the real-time monitoring data of subsidence and pore water pressure can be used to accurately determine the consolidation degree of the foundation,It can provide references for similar projects.
Study on Deformation of CFG Pile Composite Foundation of High-rise Buildings
Luo Yunhai
2019, 33(2): 97-100. doi: 10.3969/j.issn.1007-2993.2019.02.009
[Abstract](91) [PDF 856KB](17)
Abstract:
The CFG pile composite foundation deformation of a high-rise building is calculated by three recommends methods form three diferent code in Xi'an,and through the contrastive analysis of the calculated values and measured values,the applicability of different calculation methods and the reasonable values of settlement calculation experience coefficient were discussed,put forward the suitability of the CFG pile composite foundation in the high-rise buildings of the region,the deformation calculation method is proposed to the pre-design stage.
Deep Foundation Pit Technology
Study on Retaining Structures of the Large Pit-in-pit Excavation in Soft-soil Area
Wei Renjie
2019, 33(2): 101-104,120. doi: 10.3969/j.issn.1007-2993.2019.02.010
[Abstract](41) [PDF 1264KB](14)
Abstract:
Taking a foundation pit project in soft-soil area of Shanghai as an example,the retaining and protection of the pit-in-pit are expounded under different conditions in combination with the characteristics of the pit location,pit depth,surrounding environment and construction conditions.Through the analysis and research of the monitoring results,the safety and rationality of the design are proved.It would provide a good reference to other similar projects.
Multiple Retaining Technologies in Excavation Engineering
Wu Lianxiang, Jia Hua
2019, 33(2): 105-108,114. doi: 10.3969/j.issn.1007-2993.2019.02.011
[Abstract](30) [PDF 2318KB](11)
Abstract:
Retaining and protection for excavations is a temporary construction measure,aiming at earth retaining and cutting off groundwater,provided conditions for basement construction and controlled influences on surroundings.Based on an excavation engineering,multiple retaining technologies to various surroundings and solutions in the process of construction are introduced.The results could be referred for the excavation engineering of similar projects.
Experimental Research
Study on Bearing Capacity of Cast-in-place Pile in Silty Clay Area of Southern Shaanxi Province
Wang Jianan, Zhang Huihai, Chen Lin, Ren Mengtao, Zhang Xusheng
2019, 33(2): 109-114. doi: 10.3969/j.issn.1007-2993.2019.02.012
[Abstract](48) [PDF 2227KB](10)
Abstract:
The static load test of cast-in-place pile and carrier pile composite foundation was carried out on a residential construction site of silty clay in southern of shaanxi province.Combined with the theoretical calculation of empirical method,this paper compares and analyzes the advantages and disadvantages of the two schemes from bearing capacity and construction cost.The results show that the load-settlement curve of the two schemes also belongs to the slowly variation curve,indicating that both schemes can provide higher bearing capacity; When the length of the carrier pile is longer than 10 m and is used as the reinforcement of composite foundation,the expanded head benefit of pile tip resistance is not considered in the calculation process of empirical method,and the calculation result is obviously lower than the field test result.Under the same construction cost,the composite foundation of the support pile can provide higher bearing capacity than the cast-in-place pile.In the similar silty clay area of southern shaanxi,it is suggested that the composite foundation scheme of support pile should be taken priority.
Experimental Study on Treatment of Deep Soft Soil by Preloading Combined With Vacuum
He Changming, Li Jun
2019, 33(2): 115-120. doi: 10.3969/j.issn.1007-2993.2019.02.013
[Abstract](105) [PDF 2283KB](13)
Abstract:
In view of the deep soft foundation in Zhuhai,the vacuum combined loading preloading method is used to reinforce the soft foundation.During the construction process,the surface settlement,the vacuum under the membrane,the pore water pressure and the deep horizontal displacement of the soft foundation are monitored,and obtained the time dependent curve of the vacuum preloading to consolidate the soft soil foundation.After the soft foundation treatment was completed,the original soil was subjected to the vane shear tests and the load tests,and laboratory soil tests was also used in the soil.Analysis results show that physical and mechanical properties of reinforcement of the soil have been significantly improved,foundation reinforcement effect is good,the influence depth reaches to 25m~30m,and the reinforcement effect is the most significant in the range of 15 m~20 m; But the vacuum preloading does not change the thixotropy of the soft soil,and the soft soil should still avoid the disturbance after reinforcement.
Experimental Study of Pre-stressed Anchor Cables in Deep Excavations of Loess Layers
Wang Xiaoyong, Wang Yonghua, Zhang Jiwen
2019, 33(2): 121-125. doi: 10.3969/j.issn.1007-2993.2019.02.014
[Abstract](44) [PDF 1369KB](17)
Abstract:
Based on field test of pre-stressed anchor cables in deep excavations,The standard value of the ultimate bond strength in anchorage section is analyzed and calculated through measured data.It is higher than the current standard in certain loess layer when the anchor cable length is set properly.From the different load displacement curves of the test anchor cables,the pre-stressed anchor cables in loess layers and other viscous layers are basically consistent in the service conditions and load transfer,the working state of the anchor cable is reflected clearly in the curves of the test under the tension load of each stage,and the relevant fitting formula is obtained through experimental data and curves.In the end,the rigidity of the anchor cables is reverse calculated with the test data and is compared with the current standard,some beneficial results are obtained.The results can provide references for the design and construction of deep excavations in loess layers.

Copyright © Geotechnical Engineering Technique京ICP备12043220号-2

Address：No.79 Xibianmen Inner Street (Xibianmennei Dajie), Xicheng District, 100053, Beijing, P. R. China（100053）Tel：010-83117072 / 010-83196888Fax：（010）83117582Email：get099@263.net

Supported by: Beijing Renhe Information Technology Co. Ltd