Research On Cold Regions Of Deep Foundation Soil Nailing Prevention And Control Of Environmental Incidents Technology

In this paper,the deep foundation soil nailing works at home and abroad are researched,the construction and design problems of deep foundation in cold regions are analyzed,especially the shear strength characteristics of fine-grained soil changes in the parameters after freeze-thaw cycle is not considered in the design of soil nailing;Light of the specific information of the actual project construction method is used to carry out the Foundation Pit Design and Construction under complex conditions;A number of construction programs of the Deep Foundation Pit multi-goal decision-making are optimized; the situation foundation deformation, deformation mechanism and the related deformation control standards are studied and analyzed, the freeze-thaw cycle time after the deformation effect and space effect are analyzed separately, the surface subsidence caused by excavation and the surface deformation are calculated;Using FLAC3D the Deep Foundation Pit excavation and support on ZhongTian plaza are studied in the method of numerical simulation. According to the research contents of deep foundation soil nailing environmental incidents and its control technology in cold region, the research are mainly carried out from following aspects:(1) Through the investigate of the cause of the deep foundation pit slope collapse in Xinjiang south and northern areas, the main reason is found that freezing and thawing causing environmental incidents of pit slope. Response to higher soil salinity in Xinjiang, the moisture content, density, clay content and soluble salt are selected as four factors. Based on the uniform orthogonal pilot study at the four fine-grained soil slope factors as well as experiencing different cold financial cycles, the changes of shear strength parameters C,Фare studied. In the methods of range analysis, the test results are analyzed. The importance of influence factor of above four factors on the C,Фare obtained separately, and the accuracy of the results are analyzed in variance to verify the accuracy of test data.The test results prove that the actual situation and in line with the project, and it provides a theoretical basis for controlling the occurrence of environmental incidents of deep foundation.(2) Through participating in four phases works of geological reconnaissance,design,construction and deformation monitoring on the northwest highest floor, the current transit plaza deep excavation works, the foundation soil nailing design methods is summarized. And the deep excavation of the soil nailing project is designed under complex environmental conditions. For the adjacent buildings safely use without disturbed by the deep excavation and buildings without damaged, the foundation of original adjacent buildings is studied and succeed. For the safety of deep excavation works, the deformation is monitored and the monitoring results show that the excavation is successful.(3) Multi-objective fuzzy comprehensive evaluation is a simple method in the systems engineering to analysis the case of non-quantitative, and it can be as a means for people to judge in an objective description. Using multi-objective fuzzy comprehensive evaluation index weights distribution can greatly reduce the subjective factor. Through research on optimization decision-making problems of deep foundation pit construction programs, the multi-objective mathematical model is set up. It can reflect the deep foundation pit construction plan more fully and to optimize the plan more comprehensive and objective; For the problem of the process of previous multi-objective optimization calculation more cumbersome, the least bad method of fuzzy matrix is used to get the best satisfactory solution of deep excavation multi-objective optimization. It opens up a new way for multi-objective optimization of construction plan.(4) In order to reduce the impact of excavation to the surrounding environment, excavation-induced ground surface settlement is controlled. The phenomenon of deformation, deformation mechanism and the related deformation control standards of foundation are studied in this paper. At the same time, deformation time effects and spatial effects are analyzed separately. Considering the influencing factors of Kh, which is the equivalent level resistance coefficient of passive soil, especially analysis the shear strength parameters C,Фformula of fine-grained soil before and after freeze-thaw cycles, the effect of deformation of the space-time factors are considered more comprehensive and reasonable. The research of deformation estimate, and the calculation of surface settlement and deformation caused by excavation will guide the design and construction of deep foundation works in cold regions.(5) In this paper, three-dimensional ITASCA's Fast Lagrangian FLAC3D procedures are used to simulate transit plaza on Deep Foundation Pit excavation and support. The simulation results show that soil excavation in the settlement increase with the depth of excavation, and the uplift displacement of foundation at the bottom is also increase with the depth of excavation. In the central of basement, the uplift grows to the largest value of 70 mm, and near the pit wall is smaller. The horizontal displacement of soil excavation is also increase with the depth of excavation. The change trend of horizontal displacement from foundation pit wall to center is still the largest in the center and smallest in the corner, and because the long side of pit wall digs relatively in a large scope, and its deformation increases about 19 mm compared with the short side, which fully reflects the excavation in the process of space-time effects. The calculation results in this paper can provide guidance and reference for engineering design.