| In the study of mechanical properties of the soil-rock mixture,the test samples taken from the actual project consist of complex and diverse material compositions,which caused the issue:The conclusions,of which the degree of dispersion is high and verifiability is poor.In addition,the soil-rock mixture was considered as homogenous body in the experiment,and less consideration was given to the influence of macroscopic structural factors on the mechanical behavior of soil-rock mixture that was located in shallow surface(within 10 meters from the surface)in natural heap deposition environment of different projects.These problems brought great difficulties to the application of experimental results to engineering practice.Therefore,from the point of view of material composition,the compound of specific soil-rock mixture material:the degree of weathering of blocks,the type of parent rock and the mineral composition of the substrate soil were the same.On the basis of the lab large-scale triaxial tests and verification of reproducibility of test results,the influence laws of stone gradation,dry density,stone distribution,stone content,lithology and other parameters on the mechanical characteristics were explored.The test conclusions were compared with the existing research results,Try to obtain qualitative and quantitative influences of the differences of the parent rock and structural characteristics on the mechanical behavior,and preliminarily establish a specific comparison system for estimating the mechanical properties of superficially weathered soil-rock mixture,which could provide more reliable theoretical guidance for similar engineering practice.The main research results were summarized as follows:(1)By strictly limiting the identity of stones and matrix soils,the reproducibility of test data for specific soil-rock mixture under the same conditions could be ensured;The primary and secondary order of influence of macroscopic structural indicators on cohesion were:stone gradation,dry density,stone distribution,shear rate;When the coarse-grained content was high,the stress-strain curve showed jagged fluctuations in the axial strain range of 5%to 10%,eventually showing ladder-like trend;When the stone content was low,soil-rock mixture with different rock distribution structure characteristics and shear rate had three types of failure modes:approximate uniform deformation,layered deformation and bulging deformation(2)When the stone content reached 50%,the ladder-like trend of the stress-strain curve would occur earlier,and the step-like principal stress growth rate gradually increased;The step-like principal stress growth rate of soil-rock mixture increased as the uniaxial compressive strength of rock increased;When the stone had a uniform spatial distribution and the shear rate was 1.0 mm/min,the sample underwent obvious bulging deformation when the stone content was low,shear failure occured when the amount of stone was more than 50%;The relationship between the internal friction angle and the stone content was obviously partitioned.(3)The conclusions of the experiment were in good agreement with the common findings of existing studies,and conclusions different from common results,were conducive to distinguish between the phenomena and laws in the test results,but also provided more reliable theoretical guidance for similar engineering practice;Under the same experimental conditions,there were many differences in the conclusions of various literatures,which were mainly caused by weathering differences,parent rock differences,and structural differences.(4)The functional relationship between shear strength,saturated uniaxial compressive strength of stone and confining pressure,and its relationship with structural uniformity and confining pressure were established respectively;The application of the specific comparison system of soil-rock mixture was basically reliable,and it had important theoretical guiding value for related research and engineering practice. |
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