Deformation And Failure Researches Of A Dam Foundation Rock Mass Influenced By Continuous Gentle And Nonpersistent Steep Discontinuities

The main dam of Datengxia water control project under construction is near the crossbow beach,which is 6.6km away from Guiping Qianjiang Rainbow Bridge.The task of the project is flood control,shipping,power generation,irrigation and so on.The reservoir normal water level is 61.00m,and the corresponding storage capacity is28.13×10~8m~3.The main dam type is concrete gravity dam,whose maximum height is 80.01m and length is 1343.098m.The mainly exposed stratas at the project sluice gates are the 11th-13th layers of the Nagaoling Formation and the lower Yujiang State of the low Devonian.The rock formation is inclined downstream to the left bank.The structure planes on site,such as weak intercalation,plane and so on,have been developed,and the continuity is better.Therefore,under the pressure of high water head,the rock mass of the dam is prone to the holistic destruction along these structure planes.In addition,the complex structural fracture system in the base rock of the dam has been formed because of the multistage tectonic movement,which greatly reduces the integrity of the rock mass.The above factors greatly reduce the stability level of the rock mass of the dam foundation,and easily cause the dam foundation to destroy.The water has a greater thrust on the sluice gate,in order to ensure the safety of the project and fully consider the influence of unfavorable geological conditions on the foundation of the sluice gate,it is necessary to further study the failure mode and safety level of the sluice dam foundation.In this paper,the stability of 28#sluice is studied by numerical simulation through the detailed investigation of the engineering geological conditions of 28#sluice.The main results are as follows:(1)In the dam foundation,there are the limestone of the Nagaoling Formation and the Yujiang State.The strength of rock mass is high,the bedding(stratification)is developed,and it is more closed tightly,with the spacing between 10cm and 40cm.From the field survey,the occurrence of the weak intercalation is in accordance with the bedding,and the distance is 2m~5m.(2)The joints of the dam foundation are more developed.Most of the joints are smooth closed and some joints are filled with the calcite vein.Besides,the joints are not cut through the weak intercalation and the layer interface.(3)In normal conditions,numerical simulation shows that the X displacement and Y displacement of the sluice are very small and the displacement of all bedrock points is very small due to the hydrostatic pressure downstream.Finally,they all tend to be stable,so the sluice is in steady state.(4)In the overloading stage,the displacement values of numerical simulation points are increasing with the increase of overload coefficient.For the numerical simulation,when K_P=4.0,the model begins to appear plastic deformation,when K_P=8.0,the displacement of the model increases abruptly and the model is destroyed.(5)The damage area of numerical simulation is mainly the compressive failure of the bedrock under the two alveolus,and there is no penetrating structural surface deformation and damage.Among them,the rock mass of the lower reaches is moved up.The uneven deformation on the two sides of the soft interlayer under the action of super large thrust which are reflected as the expansion of the plastic zone of the rock mass and the cracking and deformation of weak intercalation and structural plane upstream and downstream.Under the interaction of the upper and lower reaches of the concrete,the bedrock bears the pressure of the pier,resulting in the deformation and failure of the Compressive plastic zone.