Research On Key Technology Of Deep Emptying System Layout And Operation Safety For High Dam With Large Reservoir

There are the largest number of reservoirs and dams in the world in China,as well as the largest number of high dams.High dams and reservoirs of more than 200 meters have been built,accounting for 1/3 of the world’s total.Most of them are built in the western border ethnic minority areas with complex geological conditions,frequent natural disasters,and complex political and social environments.In recent years,the risks of high dam and large reservoir projects have become increasingly prominent,especially the cascade hydropower projects in the basin,which may pose a serious threat to public security in case of emergencies.The research shows that the rapid lowering of reservoir water level under emergency conditions is the most direct and effective measure to eliminate danger and reinforce and maintain the safe operation of the project.But,the survey of large and medium-sized hydropower projects in China shows that most of the facilities of reducing the water level or emptying reservoirs have been set,but they only have limited ability of emptying and relatively weak operation and maintenance,and the ability of emptying reservoirs in emergency is insufficient.In this paper,a comprehensive method combining theoretical analysis,numerical simulation and model test is adopted to put forward the safety control index of deep caving in the large reservoir of high dam,create the graded water retaining caving technology and apply it to RM engineering design,forming a relatively complete design system of graded water retaining caving technology.The main conclusions obtained are as follows:（1）The safety control index of deep caving on the premise of anti-slip stability and seepage stability of dam slope is put forward.For the venting of a single hydropower project,the control of the venting process is related to the stability of the reservoir bank,the stability of the earth rock dam slope and core wall,and the surrounding seepage stability of the rigid dam abutment and dam bottom.Since there is no relevant venting control standard at present.The safety emptying depth of comprehensive dam height,slope ratio,emptying rate and other factors:the safety emptying depth controlled by 200m dam height is0.6 of the highest operating water level;the safety emptying depth controlled by 250m dam height is00.610of the highest operating water level;the safety emptying depth controlled by 300m dam height is 0.55 of the highest operating water level;The empirical formula of maximum emptying rate₈（6）is put forward.The emptying rate v should be less than₈（6）to ensure the safety of dam.（2）subject to the hydraulic gate are running water head and water flow channel high speed water flow velocity,the existing technical conditions,emptying orifice can’t set too deep,area is too large to reservoir"is not deep,not fast,can’t always realase",in view of this,put forward the"continuous multistage gate manger,stratified flow relay drain"the classification of empty water retaining technology,The theoretical system of new-type emptying technology is constructed,and a reasonable hierarchical head mode and operation mode are proposed.The function of emptying reservoir with full time,super depth and large discharge volume is realized,and the effect of rapidly reducing reservoir water level and emergency emptying is achieved,which strongly supports the major technical demand of emergency management of water conservancy and hydropower projects.（3）Through the combination of theoretical analysis,numerical simulation and model test,the hydraulic safety of the flat pressure process of the deep caving facility,the door slot of the multistage retaining gate,the aeration of the caving cavity along the way,and the structure of the sudden expansion and sudden fall behind the working arc gate is systematically studied.The hydraulic safety influence mechanism of the horizontal pressure pipe position setting and the horizontal pressure pipe diameter selection is proposed.The influence relationship of the setting and distribution of multistage retaining gate on the hydraulic characteristics of gate groove is analyzed.The complex aeration structure of"cantilever+flat（gentle）slope+steep slope"is studied,which is suitable for caving in the slow bottom slope of high head.（4）The graded water retaining and empting technology is applied to the engineering design of 300m high earth-rock dam planned to be built in China,and the cross-domain from scientific concept to engineering design is realized.A relatively complete design system of emptying system is formed,and the safety and feasibility of deep emptying technology are verified by1:15 large scale hydraulic model test.