Experimental Study On Failure Characteristics And Support Effect Of Soft And Hard Interbedded Slope Toppling Deformation In Large Scale Centrifuge

The Miao tail hydropower station is the most downstream cascade hydropower station in the development plan of the water to the end of the river in the main hydropower base of the Lancang river.The gravel soil core wall rockfill dam height is 131.3m,the crest elevation of 1414.8m than the normal water level elevation is 6.8m high,reservoir capacity is 660 million m3,the total installed capacity of 1400 MW.Miaowei hydropower station right in front of the dam slope is an anti typical layered rock slope under natural conditions,toppling deformation phenomenon is very obvious,the key technical problems after reservoir slope stability for the construction of the Department concerned.On the basis of field investigation,through the centrifuge test and numerical simulation,the deformation characteristics and support effect of slope in front of right dam are deeply studied.The main results are as follows:(1)according to the similarity principle of dimension analysis is derived for toppling deformation of slope of the centrifuge model tests,and combined with the slope site and the existing model box size selection similar coefficient,carry out the model of soft rock and hard rock,adhesive materials and material ratio test,through the test to determine the optimal ratio of similar materials for hard rock as the barite,quartz sand,gypsum,cement,water =28: 28: 27: 3: 15;to determine the optimal ratio of similar materials for soft rock barite: quartz sand: Gypsum: Glycerin: water =40: 40: 14: 1: 7;the optimal bonding material ratio of similar materials for barite.Quartz sand: Gypsum: water =5: 5: 2: 3;similar material mixing ratio for fault clay: quartz sand =3: 1;anchor selection of 0.8mm wire frame anchor structure is simulated using PVC plastic strip.(2)centrifuge test results show that the model of natural slope slope settlement,the slope displacement difference before and after the test is about 13 cm,4.6cm monitoring point displacement of the middle slope,the toe displacement 0.45 cm,slope cracks were dense,slope surface is broken;the slope deformation monitoring points of dam foundation slope monitoring points than the rate of high deformation rate shallow slope monitoring;stress value is generally parallel to the shallow slope slope sensor arranged in the deep stress value is small;the deformation and failure mode for "top seat + middle expansion + lower expansion slide".(3)the bank slope for supporting,centrifuge modeling test results show that the slope settlement compared to natural slope model supporting bank slope model of slope settlement value has been greatly reduced,the slope settlement is reduced from 13 cm to 5cm,the toe displacement from 3.65 cm to 0.91 cm,supporting slope cracks less compared to the natural slope,the slope overall is still relatively intact;the supporting toe deformation rate is less than the model of dam slope;slope monitoring point stress value is generally higher than the stress parallel to the slope surface sensors arranged on the slope in the value;the supporting bank slope mainly presents the top slight subsidence phenomenon + middle slightly bulging phenomenon.(4)using FLAC3 D finite difference numerical simulation of natural slope,slope revetment displacement and stress analysis,the results show that the natural slope slope deformation model of maximum displacement is located in the transition surface of F148 and slope,displacement of 4.56M(equivalent to the centrifuge model in terms of displacement,deformation and failure of 0.760cm)concentrated in the slope area;for slope,slope deformation and maximum displacement is also located in the junction surface F148 and slope,displacement of 1.147m(equivalent to the conversion of displacement in a centrifuge model 0.191cm);shallow slope monitoring point stress value is less than the deep stress value of monitoring points.(5)prediction of possible model of natural slope in centrifuge test phenomenon by Goodman-Bray method the results show that when the natural slope model along the shallow damage model,damage area overall slip failure;when the natural slope model along the deep damage,damage model of region along the deep sliding surface can be divided into the lower part of the middle the sliding area,dumping area,the upper stable region,and the test in the centrifuge after nearly the same phenomenon.