Study On The Physical Mechanical Properties Of Rock And Temperature Field Of Shaft Freezing Wall In Cretaceous Strata

With the natural resources of our country coal mining to the deep development, to solve the deep alluvium or water rich strata shaft construction safety problems to become the key of mine construction technology. In China, Gansu, Shaanxi, Inner Mongolia and other western regions most wellbore need through the Cretaceous and Jurassic system containing large quantity of soft rock strata, before in the alluvial layer in vertical shaft construction of freezing design parameters and experience in soft rock shaft freeze design can not adapt to. So,the research of western region deep research has important theoretical value and practical significance in engineering wall physical mechanical characteristics and temperature field development law of frozen water rich soft rock shaft.Paper to a depth of 960 m Gansu Xinzhuang Coal Mine Freezing Shaft Engineering as the background, study as the basis, using theoretical analysis, numerical calculation and field survey combining method of frozen Cretaceous thermal physical properties of the sandstone and mechanical strength properties and freezing period, shaft excavation and lining during the early Cretaceous strata in the freeze wellbore temperature field change rule, wellbore by temperature influence the stability of the studied in thawing period.From the project site take two typical Cretaceous sandstone, the coefficient of thermal conductivity and volumetric specific heat, thermal diffusion coefficient of thermal physical parameters and variation analysis of different water content and temperature, explores the two kinds of different particle size of Cretaceous sandstone thermal difference and and rock junction of tectonic relationship. The results show that:(1) the sandstone thermal conductivity decreases with the increase of moisture content show the trend of first increased and then decreased;(2) sandstone volume heat capacity as a function of the moisture increased the first slow after the steep drop, with decreasing temperature first swells after steep drop andstabilization;(3) the thermal diffusion coefficient with the increase of the water content of increased with rising until it is stabilized, with the temperature decreases slowly at first decreased and then increased gradually.Cretaceous sandstone uniaxial and triaxial strength characteristics research was carried out by MTS-815 electro-hydraulic servo controlled rock mechanical test system; analysis of saturated rock under different low temperature intensity variation, it is concluded that the relationship between compressive strength of Cretaceous sandstone and frozen temperature;analysis of the different temperature of Cretaceous sandstone elastic modulus E and Poisson’s and specific relationship with the temperature variation of mu. The results show that:(1)the value of Cretaceous system in grain sandstone, coarse sandstone uniaxial compressive strength are increased with the lowering of the temperature;(2) at the same temperature, the uniaxial compressive strength of the saturated coarse-grained sandstone is always greater than the medium grained sandstone, and coarse sandstone of low temperature grain Sawa Min;(3)the same confining pressure conditions, the lower the temperature test, saturated rock triaxial strength will be higher; at the same temperature, confining pressure and saturated rock triaxial strength is proportional to the value;(4) two kinds of Cretaceous sandstone elastic modulus increases with decreasing temperature and Poisson ratio decrease as the temperature is reduced decreases.Using ANSYS combined with the actual conditions of the Xinzhuang coal mine air shaft shaft Cretaceous strata, freezing method sinking frozen wall and shaft lining temperature field interaction change rules of finite element numerical analysis, and sums up the two walls of the temperature field characteristics. The simulation results show that after pouring the concrete wall warming significantly, and the speed of the increase of negative wall temperature time decreases, the temperature of the air convection increases causes the negative temperature time increases. During the later period of the construction, because the foam board is compacted insulation effect becomes worse, make a well in the temperature of the side of the wall into the negative temperature have an impact on the time; well temperature are the main factors that affect the scope of thaw, namely thaw with well help temperature decreased significantly reduced. By calculating the summary of outer shaft wall, freezing wall radial temperature distribution and temperature variation, to actual engineering has developed prevent measures the significance of outer shaft wall were crushed and wall crack.Carry out wellbore of Xinzhuang coal mine air shaft of the Cretaceous strata in freezing and digging puzzle in the process of temperature field and stress field field research work,including brine temperature, main rock temperature, the same rock cooling rate, frozen walland shaft lining radial temperature, pressure and the stress of steel bar freeze, on the calculation and analysis of measured data, the system summarizes the Western Cretaceous soft rock strata freezing wall expansion rate, average temperature with the freezing time variation and so on. Stages of frozen wall, the outer wall temperature was affected by the concrete water of thermal effects and freezing wall internal radial temperature field characteristic parameters, analysis and the establishment of a radial temperature distribution expression, reveal the melting of frozen wall, refreezing process temperature field variation.Study on wellbore temperature characteristics, to guide the field construction and ensure the Xinzhuang coal mine freezing shaft safety successfully completed to provide more scientific basis.