| Since the application of anchoring technology,there are too many cases of slope instability caused by excessive prestress loss.Although the standardized construction using prestress is becoming more and more perfect,due to the numerous and complex factors of prestress loss and the changeable geological conditions It is difficult to fully control the problems such as construction technology and construction technology.Therefore,it is necessary to understand the degree of prestress loss on the safety of the slope,and pay attention to the prestress loss and its impact during the long-term operation of the slope.In this paper,the unstable slope treatment project of Baidaoping Shigou in Chengguan District,Lanzhou City is selected as the research object.The support is in the form of pile-slab wall plus frame pre-stressed anchor cables and anchor slabs.The method is based on on-site monitoring,theoretical derivation and numerical simulation.The influence of the prestress loss of the frame prestressed anchor cable on the slope on its safety is analyzed.The main research content and research results are as follows:(1)Summarize the soil creep models applicable to loess.Among them,the M-2K model is more suitable for loess.Therefore,this paper establishes an MBB that is based on the M-2K model and is suitable for the coupling of anchor cables and slope creep of loess.The model,and derives its corresponding constitutive equation,relaxation equation and creep equation,theoretically solves the relationship between anchoring force change and slope creep.Taking the Baidaopingshigou Unstable Slope Treatment Project in Chengguan District,Lanzhou City as the background,the new model soil creep parameters were inversely calculated using the MATLAB programming algorithm,and the MBB model was fitted with the monitoring data and compared with the existing MKB model.It was found that The MBB model is more suitable for high slopes in loess areas and can be used to predict changes in prestress.(2)Use the slope failure form of the logarithmic spiral slip surface to construct the single-stage and multi-stage frame prestressed anchor cables(including the pileslab wall)supporting slope models,and use the plastic mechanics limit analysis upper limit method to construct the symbolic slopes The functional balance equation of the limit state is solved by the genetic algorithm program written by MATLAB to solve the safety factor,and the change of the safety factor of the slope supported by the singlestage and multi-stage frame prestressed anchor cables is observed by continuously reducing the numerical value of the prestress in the formula.In order to determine the role of prestress in the long-term development of the slope.(3)Orthogonal experimental design method is used to analyze the parameter sensitivity that affects the stability of the single-stage and multi-stage frame prestressed anchor cables to support the slope.By changing the parameter values in the functional equation obtained by the upper limit analysis method of plastic mechanics Obtain different test results(safety factors).It was found that the factors affecting the safety factor of single-stage and multi-stage slopes differ according to the order of influence from large to small.The order of prestress as an influencing factor has also changed greatly,and it can be found that the prestress factor is important whether it is in the single-stage frame frame pre-stressed anchor cable supporting slope or the multistage frame pre-stressed anchor cable supporting slope.Sex is obvious.(4)Numerical simulation of the unstable slope treatment project in Baidaoping Shigou,Chengguan District,Lanzhou City was carried out by FLAC3D software,and the safety factor was calculated and compared with the result obtained by the upper limit analysis method of plastic mechanics;The stress value is used to observe the slope horizontal and longitudinal displacement,the maximum velocity vector and the change of the plastic zone. |
PDF Full Text Request