Meso-Numerical Calculation Of Crack Mechanism Of Concrete On Inner Wall Of Deep And Large Frozen Shaft During Sinking Period

Phase for the study of sinking deep freezing shaft wall concrete cracking mechanism,the wall of mesoscopic structure damage and its macroscopic mechanical response to build links,from the Angle of the mesoscopic,combined with the hierarchical placement method and the random walk method based on the random parameters of random aggregate of concrete wall mesoscopic numerical model and simulate the borehole wall due to hydration heat in the process of casting and the contraction causes the whole process of cracking,phase has been sinking deep freezing shaft wall concrete cracking mechanism,and the wall thickness,concrete strength and constraint conditions discussed three factors.First of all,according to the concrete distribution theory and the monte carlo method,established the aggregate particles,mortar matrix,aggregate,mortar bond interface layer of three-phase aggregate random location,shape,random thermal mechanics parameters of the mesoscopic concrete model,expand the stratification is put on the train of thought,method of aggregate on the efficiency to a certain extent improve the aggregate and discreteness;The shape of aggregate,the idea of meshwork division and its applicability were discussed in turn,and the constitutive relations of tensile,compression and shear damage,the maximum tensile strain,molar coulomb failure criterion,the meso-thermal parameters and mechanical parameters of aggregate,mortar and interface varying with casting time and temperature were determined.Secondly,by verifying the thermal parameters of the concrete specimen model,the heating rule that the hydration heat develops rapidly from the mortar part to the aggregate part at the early stage of concrete pouring is obtained.The relationship between the macroscopic thermal conductivity system and time is obtained by simulating the thermal conductivity rate of the specimen,and then the meso-thermal parameters are obtained and its rationality is verified.Then,the uniaxial compression and uniaxial tensile simulation tests were carried out on the models respectively.The results show that the failure process of the specimens starts from the interface area unit,and then develops to the mortar part after forming the bond crack,and finally forms the main crack.Through the stress-strain curve and secant modulus-strain curve,the threephase meso-mechanical parameters of aggregate,mortar and interface layer of C60,C70 and C80 concrete with age were obtained,which verified the rationality of the concrete model.Thirdly,a double-layer borehole model of the mesoscopic inner wall was established to simulate the change law of temperature field in the process of chemical and thermal generation of pouring water in the real inner wall,and the development law of cracks in the inner wall was obtained.The results showed that the inner wall temperature experienced five stages: induction period,rapid warming(1.83?/h?6.45?/h),slow warming(0.77?/h?1.78?/h),rapid cooling(0.51?/h?0.74?/h)and slow cooling(0.14?/h?0.49?/h).In the phase of 0h?20h,no cracks are formed in the inner wall foundation.During 20h?40h period,due to the large temperature difference between the inner and outer edges(above 40?),mesointerface elements were subjected to tensile damage and developed continuously by temperature stress,and toroidal cracks and a small number of vertical cracks began to appear at the inner edge of the inner wall.In the 40h?80h stage,due to the accumulation of autoshrinkage deformation(150???300??),the vertical crack develops.In the early stage,the circum-fracture stress concentration produces the circum-crack,and finally the "cross" crack is formed at the inner edge.The single factor analysis was carried out for inner wall thickness,concrete strength and inner and outer wall constraint conditions.The results showed that :(1)the temperature difference of different inner wall thickness ranged from 1.00? to 24.39?,and the damage degree of inner wall decreased from7.29% to 2.80% with the increase of thickness.(2)The temperature difference of concrete with different grades ranges from 0.33? to 2.03?,and the damage degree of inner wall decreases from 4.68% to 4.54% with the change of grade C60 to C80.(3)The application of plastic plate has a great influence on the vertical stress and strain values at the outer edge of the inner wall,but has no influence on the base at the inner edge.Through this paper,the modeling method of stratified random walk,set up the simulation stage sinking deep freezing shaft wall cracking of concrete mesoscopic model,obtained the C60 ? C80 concrete change with temperature,age of mesoscopic reveals the wellbore wall around the thermal and mechanical parameters in internal and external causes temperature difference and its shrinkage effect,take the lead to tensile failure interface unit,further development to bond crack and affect mortar unit eventually formed "ten" word macro cracking law of toroidal,vertical cracks,crack sidewall of actual construction and field work has a certain practical significance.The paper has figures of 160,tables 26,95 references.