Research On The Stress Law Of Inclined Shaft Lining In Surface Soil During Frozen Wall Thawing Process

In the project of shaft sinking by freezing method, the stress law of inclined shaft lining during frozen wall thawing process, was a research blind spot in the past inclined shaft lining construction project. And during the frozen wall thawing, the inclined shaft lining was influenced by temperature field, water field, stress field and other fields, it was in a complex stress condition. If we carry out research work of this period, it would be greatly helpful to the design and construction of inclined shaft lining. The stress law of inclined shaft lining in surface soil during frozen wall thawing process was studied by combining the method of numerical simulation and model experiment in this paper.In numerical simulation, firstly, a plane model was established by the test device to verify the feasibility of hydraulic bladder loading system. Then, the relevant parameters that may affect the loading system were analyzed on that basis. Finally, through the sequential coupling method, the stress law of inclined shaft lining during frozen wall thawing process was obtained by coupling analysis of the temperature field and the stress field. The result of simulation showed that the use of hydraulic bladder and water pressure loading system together to achieve triaxial loading effects of the enclosed space was feasible. It also revealed that, the impacts of thickness of compression plate and soil horizontal lateral pressure coefficient on loading effects were relatively large in the loading process. The conclusion indicated that the stress of key points of inner edge and outer edge basically showed a gradually increasing trend during frozen wall thawing process. The maximum radial displacement occurred in inner invert arch center, the maximum tensile stress occurred in inner top arch center of shaft lining. The two points were in the most unfavorable state in all key points. So, they should be well considered in the process of design and construction.In model experiment, the size of steel model shaft lining was determined by numerical calculation at first. And on that basis, four simulation experiments of shaft lining stress were conducted by that model. They were the hydrostatic pressure test, the ground pressure loading test, the combined effects of ground pressure and pore water pressure test, and the frozen wall thawing loading test. The study of the hydrostatic pressure test showed that, there was no effect if circular steels at ends of the steel model shaft lining exsited or not. And the result of circumferential strain of model experiment was basically consistent with the conclusion of numerical simulation. The ground pressure loading test revealed that the circumferential strain at the inner center of invert arch and top arch, linearly increasing with the increase of Y-direction load Yp. WhenYp was certain, the circumferential strain at the inner center of invert arch decreased with the increase of X-direction load Xp. In the combined effect of ground pressure and pore water pressure test, thecircumferential strain at the inner center of invert arch increased while the pore water pressure raised. The circumferential strain at the inner center of the top arch was contrary to that. In the frozen wall thawing loading test, the temperature stress of shaft lining model inhibited tensile stress of the inner top arch and invert arch center which was caused by pore water pressure during thawing process. The circumferential strain at the inner center of invert arch and top arch decreased, which was inconsistent with the result of numerical simulation while the temperature of frozen wall raised.At last, the main conclusions were reached by conducting numerical simulation and model experiment. And also, several recommendations were put forward to modify the lack of the research work.