Study On The Stability And Early Crack Resistance Of Hydraulic Tunnel Lining Under The Condition Of High Geothermal

With the rapid developing of the social economy and engineering technology, the underground engineering gradually became the main subject of national infrastructure. All kinds of geological disasters' prevention, especially the difficulties of the high geothermal tunnel in the process of designing and construction, gradually became the focus of scholars all over the world. This article uses the theoretical calculation method, calculates the temperature field and stress field of tunnel lining structure under the condition of high geothermal, and the design principle of the thermal insulation layer has carried on the related discussion. On this basis, using the ANSYS software, we run related numerical simulation of high geothermal geological disasters in the case of the diversion tunnel lining of Xinjiang Taxkorgan River qirehataer hydropower station, provides a theoretical basis to determine the reasonable supporting structure. In order to study the early crack resistance of tunnel lining concrete under the condition of high geothermal, we tested the influence of temperature, water-binder ratio and dosage of fly ash to the early crack resistance of high performance concrete by knife-edge method. The main conclusions are as follows:(1) Thermal insulation set between surrounding rock and concrete can significantly reduce the temperature difference of the concrete lining and temperature stress produced by temperature and fixed constraint. Calculation formula of temperature field and stress field are also given in this paper, the related design principles of the thermal insulation layer is given according to an engineering example.(2) We run numerical simulation of the construction period stability of the diversion tunnel lining under the condition of high geothermal tunnel, respectively analyze the impacts of heat insulation layer, water cross section shape, structure' maximum stress and structure anti-seismic factors on the stability of the supporting structure. The calculation results show that the stability of hydraulic tunnel lining is best with free flow in circular section and lining thickness is 25 cm.(3) We run numerical simulation of the operating period stability of the diversion tunnel lining under the condition of high geothermal tunnel, respectively calculate the equivalent stress, structure displacement and safety coefficient of different monitoring points. The calculation results show that the supporting structure of spray anchor bracing + thermal insulation layer + model built of reinforced concrete can meet the demand of practical engineering under the condition of high geothermal.(4) The orthogonal experiment shows that increasing temperature can reduce the early crack resistance of concrete, fly ash can improve the early crack resistance of concrete when60?. The best dosage is 25% and the optimal water cement ratio is 0.47 tested by the experiment.