Study On The Frozen Wall Development Law Under The Condition Of Freezing On Local Inner Surface Of Vertical Shaft Lining

Since 1987,140 shaft walls in deep soil layers in China have been fractured,which has caused huge economic losses and formed a major mine safety hazard.In order to control this kind of disaster,the method of reconstructing shaft lining structure is mainly used.When the shaft wall is reconstructed by full depth freezing outside the well,not only the cost is huge,but also the freezing hole construction is difficult and the construction period is long.In this paper,a low-cost,easy construction,short construction period of local freezing technology in the well is proposed.Through the combination of numerical calculation and physical simulation test,a comprehensive and in-depth study is carried out.The main results are as follows.Firstly,based on the similarity theory,the variation law of temperature field in the process of local freezing in the well is studied by similarity numerical calculation.Single factor numerical analysis is used to determine the reasonable shaft insulation range,freezing pipe spacing and height of pipe laying area;the influence of soil moisture content,shaft wall thickness and other parameters on freezing temperature field is mastered;The relationship between the dimensionless freezing wall thickness,average temperature and the dimensionless parameters is obtained,and the dimensionless calculation formula is obtained through the regression of the full combination calculation results.Secondly,using the designed physical simulation test-bed,the local freezing simulation test in the well is carried out,and the development law of freezing temperature field of clay and saturated sand in different stages is revealed.The test results show that: during the slotting process,the temperature rising phenomenon of the frozen wall in the center of the slotting section is the most significant,the maximum temperature rising range is up to 50%,and the temperature rising rate gradually decreases with time;after the slotting stage lasts for 32 days,there is no melting phenomenon inside the frozen wall in this area,the frozen wall continues to develop to the periphery,and the frozen wall thickness continues to increase in the process.In this paper,through the combination of numerical calculation and physical simulation test,the development law of the freezing wall under the condition of local freezing in the well is obtained,and the feasibility and reliability of the freezing technology are confirmed.The research results have important practical value and guiding significance for the control of the wall fracture disaster.The paper contains 143 figures,30 tables and 78 references.