Experimental Study On Joint Bearing Capacity Of Crescent Steel Bifurcation

With the lucubrating of penstocks in hydropower station in resent years, underground crescent steel bifurcation became applied widely. However, the underground crescent steel bifurcation is usually designed as exposed penstock at present while the resistance of surrounding rock is considered as an excess safety repertory. The studies about joint bearing capacity of steel bifurcation, concrete lining and surrounding rock are scarce. In this paper, the stress distribution features and internal water pressure transfer rules of this joint bearing structure were studied. A normal designing measure of steel bifurcation was also provided.First of all, the in-site model tests about steel bifurcation of Xilongchi pumped storage hydropower station were analyzed. By comparing the stress distributions of exposed penstock and underground penstock, the resistance of concrete lining and surrounding rock and internal water pressure transfer rules were studied.Then, three-dimensional models of this crescent steel bifurcation were analyzed by MSC.Patran and Abaqus software. With these models, the joint bearing capacity of steel bifurcation, concrete lining and surrounding rock was studied. In some models, a special element type, which is named GAP was applied. GAP elements made it possible to simulate the contact relationship of shell-metal casing and surrounding concrete, from separation to binding. The rules of stress distribution and internal water pressure transfer were studied thoroughly.The result showed that the stress of underground penstock was better than the exposed penstock. Changing the initial gap size or adjusting the parameters of concrete lining and surrounding rock could adjust the stress distribution. The concrete lining and surrounding rock took important roles under the action of internal water pressure. Considering the bearing capacities of the concrete lining and surrounding rock can reduce the thickness of the steel bifurcation. The outcome is useful for engineering practice.