Similar Material Research For Structure Model Of High Geothermal And Pressure Hydraulic Tunnel

This paper depended on the funding project of National Science Foundation: Research of the load-bearing characteristics for high geothermal gradient and pressure hydraulic tunnel under the action of THM coupling, (NO. 51369007.),aimed at the few problem in similar material structure model test research of high temperature and pressure hydraulic tunnel, based on the mechanical characteristics of high geothermal and pressure hydraulic tunnel, the paper develops similar material for structure model using the similitude theory of the model tests, which makes up the lack in similar material research for structure model of high temperature and pressure hydraulic tunnel. By way of proportion test, a new model material is prepared using cement, sand, gravel, barite powder and other raw materials. The new model material has some advantages of good thermal stability, ease of construction and a wide range for adjustment of mechanical properties parameters. We get physical parameters of the similar material by means of mechanical property testing and linear thermal expansion coefficient testing, and analyze the influence of content of raw materials on mechanical property parameters of the similar material by testing. Then we assign the value of mechanical property parameters of the similar material to the simulation model of structure model experiments, and simulation for high geothermal and pressure hydraulic tunnel is conducted to analyze the mechanical characteristics and failure mode of the structure model of high temperature and pressure hydraulic tunnel, which can provide some references for model experiments. The main results of this study are as follows:(1) For the mixture ratio of similar material test, physical parameters with compressive strength, tensile strength and elastic modulus is texted. After compared with that of archetype rocks, then two groups of test mixture ratios are determined as the similar material of model experiments. These physical parameters meet the requirement of II type rock and III type rock for model experiments respectively. Through total analysis of the relation between different content of similar material and test results of mechanical material properties, we get the influence of contents of the raw material on compressive strength, tensile strength and elastic modulus:the increase of cement content, barite powder content, stone content and the decrease of water-binder ratio, will lead to tensile strength, compressive strength and elastic modulus increase.(2)Through the test of coefficient of linear expansion, we get the coefficient of linear expansion selected, which meet the range of the similar material.(3) Through the simulation of structural model test, the simulation conclusions are got that:when the water filling, thermal convection under the surrounding rock and the water of tunnel, the structure model of high temperature and pressure hydraulic tunnel produce temperature gradient. Effect of the tensile stress of surrounding rock is obvious and bearing capacity of surrounding rock is lower than general high pressure hydraulic tunnel model, so temperature effect cannot be ignored; Under the coupling of temperature field, seepage field and pressure field, the force of the structure model of high temperature and pressure hydraulic tunnel is complex. So we should choose reasonable T-H-M coupling model to calculate. Under the action of coupling, the surrounding rock formed divergent crack and a few cracks developed deeply, then appeared hydraulic fracture.