Research On The Thermophysical And Mechanical Properties Of Artificial Freezing Calcareous Clay In Deep Buried Strata Of The Huainan-huaibei Mining Areas

Artificial stratum freezing curtain is used as a temporary support measure for underground structure engineering,which creates "dry ground" construction conditions for underground construction.Freezing curtain not only needs to meet the sealing water requirements,its strength to meet the engineering safety construction requirements is also the most important design.In this paper,the calcareous clay in deep stratum is taken as the research object,and the experimental study on the thermal physical and mechanical properties of artificial freezing is carried out from the micro and macro perspective.The freezing characteristics,basic physical and mechanical properties,micro-structure and macro-mechanical properties of calcareous clay in deep stratum are deeply explored.The reason why calcareous clay is "difficult" to freeze is revealed from the micro and macro perspective.Then the relation and influence of mechanical properties are discussed.Through the systematic study on the micro and macro characteristics of calcareous clay,it provides theoretical support for solving the safety problems such as large rheology,low strength and frequent pipe breaking accidents that occur when the frozen shaft is driven through the calcareous clay layer in Lianghuai mining area,which has important theoretical significance and engineering application value.The thesis mainly completed the following research work:(1)By studying the soil and water characteristics of calcareous clay under different salinity conditions,the freezing characteristics and soil-water characteristic curves of total suction,matric suction and osmotic suction of saline calcareous clay in Huanghuai area were tested and analyzed,and the mathematical model suitable for accurately describing the soil-water characteristic curve of saline calcareous clay was determined by comparative analysis.The soil-water characteristic curves of total suction,matric suction and osmotic suction of calcareous clay were drawn,and the mathematical model describing soil-water characteristic curves of saline calcareous clay was obtained.(2)For deep-buried calcareous clay,laboratory experiments were carried out on the thermophysical properties under the interaction of multiple factors such as salt content,water content and temperature,to explore the influence of various factors on thermal conductivity,freezing temperature and water and soil characteristics of deep-buried frozen calcareous clay,as well as the relationship between matric suction on freezing temperature and thermal conductivity,and to explain the internal relationship and change relationship from a micro-macro perspective.The relationship between calcareous clay freezing temperature and water content and salt content was obtained.(3)The macro-physical properties of frozen Calvary clay under different temperatures,different water content and salt content were tested.Based on the above studies,the main factors affecting the strength of Calvary clay were proposed,and the true triaxial orthogonal test with 5 factors and 4 levels was carried out to explore the primary and secondary order of the influence of each factor on the strength of frozen soil.The influence weight of each factor on the strength of frozen calcareous clay was discussed through multi-factor interaction analysis.The strength characteristics of frozen saline calcareous clay and the interaction of various factors were obtained.Figure [76] Table [15] Reference [116]...