| There are navigable buildings in high mountains and canyons in southwest China,Inevitably,it involves the excavation and unloading of high and steep slope under complex geological background.The mechanics theory of unloaded rock mass has been widely used in practical engineering.However,it is rare to use model test to study excavation unloading of high and steep rock slope under complex conditions.Compared with numerical simulation,model test can not only reflect the spatial relationship between structure and geological structure,simulate structural planes such as joints and faults,but also intuitively show the whole process of internal deformation and failure of rock mass of high and steep slope.Therefore,based on the engineering geological data and related literature of the dam area of Wudongde Hydropower Station,this paper determined the material ratio similar to the hard limestone through orthogonal test,used the physical model test to simulate the high and steep rock slope,and studied the excavation unloading effect of the physical model under the condition of no and containing structural plane.Specific research contents are as follows:(1)Based on the geological conditions of the high and steep rock slope of Wudongde Hydropower Station on Jinsha River,the similarity scale of model test is deduced by combining with the similarity theory.Barite powder,quartz sand,rosin alcohol solution and high strength gypsum powder are selected as the raw materials of similar materials,and the ratio of similar materials is determined by orthogonal test method.The effect of curing temperature on mechanical properties of similar materials was also studied.The results show that increasing curing temperature can not only ensure the stability of mechanical properties of specimens,but also significantly shorten the molding time of materials.(2)A physical model loading test device was made,and a multi-point optical fiber displacement sensor based on Bragg grating was designed independently,and the verification test was carried out.The sensor has the advantages of high precision,high sensitivity,small size,high temperature resistance and durability,large strain range,etc.It can realize remote multi-point distribution and real-time monitoring,and solve the problem of monitoring the whole process of the deformation of the monitoring point in the model.(3)The simulated in-situ stress was applied to the physical model without structural plane and with structural plane.The internal stress response of the physical model was analyzed in the loading process,and the initial stress distribution of the physical model without structural plane and with structural plane was obtained.The influence of down-dip and anti-dip structures on the initial stress distribution of the physical model was studied.The results show that the stress distribution of the physical model decreases along the conduction direction after loading,and there is a stress concentration phenomenon near the structural plane.(4)The excavation unloading tests were carried out for the model without and with structural plane respectively,and the stress and displacement variation rules of the high and steep rock slope during the excavation process were analyzed.It is found that during the excavation process,the stress variation law is firstly increased and then decreased,and the displacement first decreased and then increased.High in-situ stress area appears in a certain range at the bottom of the excavation area,and there is stress concentration phenomenon in the area near the structural plane during the excavation process.It is indicated that in the process of excavation,the stress in the rock mass of slope is not only simply released,but also increased due to the influence of the high stress area.(5)The unloading rate and displacement of the model without and with structural plane after excavation are compared and analyzed respectively.It was found that the unloading rate and displacement of the rock mass on the inclined structural plane increased significantly.For example,the stress unloading rate at the T5 monitoring point increased by 55.60%and the displacement value increased from 1.67×10-2mm to 2.91×10-2mm.The existence of antidip structural plane reduces the excavation unloading effect of rock mass.(6)Based on the mechanics principle of unloaded rock mass,the excavation unloading area of high and steep rock slope is divided according to the stress unloading rate as the index,and the related verification is carried out with the monitoring points.It is found that the range of strong and weak unloading zone of the upper rock mass increases significantly due to the inclined structural plane,and the influence range of unloading zone decreases due to the existence of anti-inclined structural plane. |
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