Engineering Properties Of Sandy Pebble Soil Without Water Research

With the further study of geotechnical mechanics in the world,people have come to realize that we want to know more about the mechanics of geotechnical mechanics.And due to the sandy pebble soil’s discrepancy and shape regularity,CDEM can be used to observe its mesoscopic activity of the process,so as to analyze the mechanical properties at the microscopic angle.In this paper,PFC2 D / 3D is used to analyze the microstructure and mechanical properties of sandy pebble soil by the popular numerical simulation of particle flow,and try to get the intrinsic relationship between the microscopic and macroscopic properties of sandy pebble soil to describe its mechanical characteristics.The sandy pebble soil stratum is one of the most complex geologic forms that are often encountered in underground construction.For example,the sandy pebble soil stratum encountered in the construction process of Chengdu subway is a typical water-rich sandy pebble soil.In the process of construction of Beijing subway,Pebble bottom also exist.The main features of the sandy pebble formation are the strong dispersion type and the strength of the pebbles itself is higher than that of other fine soils(fine-grained soils)Also,it includes the geometrical regularity and individual shapes can be largely categorized.Under these common characteristics,sandy pebble soil show complex mechanical properties,so that the underground tunnel construction is facing a great difficulty.Only under the premise of knowing the microscopic mechanism of sandy pebble soil,We can analyze these problems and difficulties to overcome.At present,the mechanical properties of sand gravel are based on a lot of theoretical and experimental basis,but most of them are based on finite element analysis with some limit.Therefore,this thesis establishes the basic mechanical test model(stacking test,triaxial Test,active door experiment)by discrete element.The whole process of the indoor test is simulated by the boundary servo control.In terms of these basic numerical simulation tests,the basic parameters for the indoor test are provided.Based on the existing theoretical basis,this thesis studies the mechanical characteristics of waterless pebbles by means of discrete element method.Based on the obtained data and indoor experiment and field examples,this thesis makes a theoretical basis for the construction of sandy pebble soil stratigraphy.The The main research contents are as follows:1)Systematically classified the individual characteristics and microscopic characteristics of sandy pebble soil,such as shape,particle size distribution,self coefficient of friction,stiffness and so on.2)Break the limitations of traditional finite element method,PFC program is a more direct simulation test process,with use of the program built-in language for secondary development to establish irregular particle model,proving that PFC can be a good simulation of mechanical properties.The different macroscopic and mechanical properties of different shapes and different parameters are systematically analyzed.3)Through the indoor experiment and numerical simulation,the bulk particles under different parameters were compared and analyzed,and their internal regularity was obtained,revealing the interaction between the meso-scale.4)According to the above conclusions and the actual project confirmed to further explain the sandy pebble soil stratum tunnel construction and the impact of changes for the future construction of sandy pebble soil to provide a strong basis.