| After a large reservoir is built and operated,the water level changes periodically with the reservoir operation.For example,the baihetan reservoir on the jinsha river,which will be completed in 2022,will see a 60 m change in water level.After the completion of the reservoir,the bank slope in the stable state may be excessively deformed or even unstable due to the periodic change of the reservoir water level,so it is necessary to study it.Xiaojiang bank slope is located in the downstream area of baihetan reservoir,and its slope material is gravel soil.It is a typical bank slope soil type in baihetan reservoir area.The study on its stability has important practical significance for the stability evaluation of a large number of similar bank slopes in baihetan reservoir area.In this paper,the physical and mechanical properties of the gravel soil along xiaojiang river are studied by field test,laboratory test and numerical simulation.The main research work and results are as follows:Through the field test,this paper discusses the mechanical and physical properties of gravel soil,through compass method and gravel soil excavation method to get the the spot of the specific conditions of the natural Angle of repose and the Angle of repose,through alcohol burning method and the sand filling method and the specific situation of the natural density,the moisture content through the sieve analysis method to get the particle gradation.Studies have shown that there is a relationship between the resting Angle of particles and the gradation uniformity of particles,and it is also related to the moisture content of particles.The size of the moisture content will affect the cohesive force between particles,and the underwater resting Angle will have degradation effect compared with the natural resting Angle,which will lubricate the particles and cause the underwater resting Angle to become smaller.Indoor undisturbed soil was obtained through on-site soil collection and treatment,and the natural and saturated shear strength of the soil was obtained through indoor medium direct shear test.The permeability coefficient of saturated gravel soil was obtained through constant head method,and the maximum dry density and optimal moisture content of gravel soil were obtained through heavy compaction instrument.Study surface: the shear strength of saturated undisturbed soil decreases compared with that of natural undisturbed soil,mainly due to the lubrication effect of particles.With the increase of vertical load,the loss value of shear strength also increases.The corresponding densities under different densities were obtained by compaction test.Based on the theoretical basis of resting Angle,the resting Angle tester was made by ourselves.The resting Angle of water and water with different densities and particle sizes was obtained through injection and discharge methods,and the influence of different Cu values on the resting Angle was studied.The results show that the Angle of repose increases first and then decreases with the increase of particle size,and the Angle of repose under water increases all the time.For different compactness,also in the process of gradually increase,the Angle of compactness of the faster,the greater the increase,to show the same trend of water and the Angle of repose Angle of underwater differs at about 8 °,is gradually increasing with the Angle of repose,the smaller the water loss rate.For the rest Angle under different gradations,with the gradual increase of Cu value,the rest Angle also increases gradually,indicating the effect of uniform distribution of gradation on the rest Angle.By using the three-section method in the bank collapse prediction,the left,middle and right sections of the small river bank collapse were predicted,and the stability analysis of the three sections was put forward by software named geo-studio.The results show that the stability of the three sections is good,and the safety coefficient is greater than the engineering requirement of 1.1. |
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