Experimental Study On Physical And Mechanical Properties Of Xinzhuang Mine Cretaceous Sandstone Under Freezing Conditions

In recent years，with the process of coal exploitation in China gradually develop to thewest and deep well, there has a climax of the new wells construction in Shaanxi, Gansu, InnerMongolia, Xinjiang and other western regions. And the region coal field is covered with amass of cretaceous strata, which has characteristics of rich water, low strength, weakcementation, argillization, etc. Freezing method has unique advantages for support scope anddepth in water-bearing strata, already become one of the most effective special constructionmethods for shaft to across the deep bedrock. To experimental study on the characteristic ofphysics and mechanics of freeze cretaceous sandstone, which will provide basis parametersfor the west mine freezing design and stability study, and also play a positive role in enrichingour country theory of rock and soil mechanics.The article was based on the background of xinzhuang coal mine shaft freezing windproject in Gansu province, made a comprehensive study to the physical and mechanicalproperty of representative cretaceous rich water strata rocks when the shaft through. First,analyzed western cretaceous strata characteristics, geological structure and hydrologicalgeology characteristics, observed the microstructure characteristics of sandstones by scanningelectron microscopy (SEM), experimental studied on the characteristics of conventionalphysical parameters of sandstones, systematic analysed the particularity of cretaceous stratafrom macro to micro; in-depth analysed the thermal physical properties of sandstones underdifferent moisture state and different low temperature, and its influencing factors;systemresearched uniaxial mechanical characteristics of cretaceous sandstones with different lowtemperature, fitted for the relationship between uniaxial or triaxial compressive strength offrozen rock and temperature; comprehensive analysed of the whole stress-strain curve and deformation rule which conclude axial and volumetric strain of freeze cretaceous sandstones,emphasis discussed the correlation between elasticity modulus and poisson ratio of rocks withtemperature. Finally, expounded the deformation and failure process of cretaceous rocks anddestruction form.The result shows, characteristics of cretaceous sandstones are water-rich, macropore,argillace-ous cementation and small frozen deformation. The difference of thermophysicalproperty of two cretaceous sandstones is large, under different water content and lowtemperature. The uniaxial compressive strength of saturated rock is increasing with lowtemperature, and the strength of gritstone is always greater than medium sandstone. The lowertemperature and the larger confining pressure, the greater triaxial compressive strength ofcretaceous rock.The deformation of frozen rock experienced four stages conclude porecompaction, elastic and plastic deformation and strain softening. With the decrease oftemperature, elastic modulus is increasing, poisson’s ratio is reducing, account for plastic offrozen rock is abating, brittleness is increasing, and the main damaging form of cretaceousrocks is tension damage.