The Optimal Design And Its Application Of Loess Cutting High Slope In Low Hilly Area Of Lanzhou

Under certain conditions of slope material and structure,the slope shape is the main factor to control the stability of the cutting high slope.The slope shape of the cutting high slope is composed of four elements:slope height,slope rate,platform height and berm width.How to balance the four factors and determine the safe and economic cutting slope is one of the difficult problems in engineering practice,and it is also one of the hot issues in geological engineering.In the low hilly area of Lanzhou,a large number of cutting slopes have been formed due to removing the mountains project.The stability of these cutting slopes is directly related to the safety of residents'life,property and engineering facilities in the project area.Therefore,systematically researching the optimal cutting slope plan for loess high cutting slope in the low hilly area of Lanzhou is not only of practical significance and practical value to the urban development of Lanzhou,but also has significant theoretical significance in the design of cutting slope of geological engineering.Based on the characteristics of the cutting slope of the loess loess in Lanzhou,this paper adopts orthogonal test method to design 1080 models of cutting slopes with different slope height,slope rate,platform height and berm width.The SEEP/W module and SLOPE/W module in GeoStudio software were used to simulate and calculate the slope seepage field under rainstorm conditions and the stability under natural,rainstorm and seismic conditions.Sensitivity coefficient method and orthogonal test method are used to analyze the sensitivity of slope stability to slope shape parameters.Based on the calculation results,the safety and dangerous slope-shaped enveloping surface of Lanzhou loess cutting slope was constructed based on MATLAB tools.An optimal cutting slope plan that meets the safety and economic principles is proposed.The slope stability envelope proposed in this paper is used to qualitatively evaluate the slope stability of the Pacific site in Chengguan District,Lanzhou,and verified by quantitative evaluation results.FLAC^3D was used to simulate the displacement and stress characteristics of the cutting slope in the Pacific Ocean under seismic conditions.The deformation and failure zone and its deformation failure model of the slope were predicted.The main results of the thesis are as follows:?1?Under natural,rainstorm and seismic conditions,the slope stability of Lanzhou loess cutting slope decreased sharply with the increase of slope height,the number of dangerous slopes increased,and the number of safety slopes decreased.Under natural conditions,slopes of 30m and 60m are relatively stable on the whole,while the stability of 120m and 150m slopes is significantly reduced.When the slope height is the same,the difference between slope stability and natural conditions is smaller under storm rainfall conditions.Under the seismic conditions,the slope stability is significantly lower than that of natural conditions,and the number of dangerous slopes increases,and with the increase of slope height,the change is greater.?2?At the same height,the stability of the cutting slope is negatively related to the slope rate,and platform height,and is positively related to berm width.Sensitivity coefficient method and orthogonal test method have the same results for the sensitivity of the slope shape parameter to the slope stability,from high to low is:berm width,slope rate,platform height.Among them,the orthogonal test method used the F-test of the given significance level?of the three factors,and it was found that the impact of the berm width and slope rate on the stability of the slope was highly significant,and the platform height was influential but not significant.?3?The MATLAB tool can easily form a safe and dangerous slope-shaped envelope surface with different slope height under different conditions.The envelope surface can be used to analogically evaluate the stability of the slope with the same material and guide the slope design.On the basis of safety slope shape parameters,comprehensive small single-width cuts,and large excavation lengths of slope foot proposed the optimal slope profile of the cutting slope with similar nature to loess in the Lanzhou area under different slope height:The optimal cutting slope plan for 30m slope height is 9m platform height,1/0.3 slope rate and 3m berm width;The optimal cutting slope plan for 60m slope height is 7m platform height,1/0.5 slope rate and 5m berm width;The optimal cutting slope plan for the 90m slope height is 8m platform height,1/1.2 slope rate and 3m berm width;The optimal cutting slope plan for 120m slope height is 6m platform height,1/1.2 slope rate,4m berm width,and the optimal cutting slope plan for 150m slope height is 5m platform height,1/1.1 slope rate and5m berm width.?4?Based on the safety and dangerous slope-shaped envelope surface stability evaluation results and quantitative calculation results are basically the same.Under earthquake conditions,the slopes of I-I,II-II,III-III,and IV-IV are in a state of instability or understable,and the V-V and VI-VI slopes are in a basically stable state.The comparison results show that the use of safe and dangerous slope envelope surface for the slope stability analogy evaluation has a higher credibility.?5?The FLAC^3D simulation results show that the displacements of slopes show a gradually decreasing variation from the surface to the deep and from the back to the front,and the displacements are greatest in the second half of the surface of the slopes III-III and IV-IV.There are more tensile plastic zones at the top of the slope,and there are more shear plastic zones in the slope foot and in the slope.From the side of the slope,there appears a zone of penetrating plastic zone in the slope,and along the plane of the IV-IV section,it can be seen that the zone of the plastic zone in the slope has also penetrated.The slope stability factor calculated by the strength reduction method is 0.996.It indicates that the slope will lose stability under the earthquake conditions,and the slope deformation and failure mechanics model has the characteristics of creep-stripping.