Investigation Of Multi-field Coupling Problems In Geotechnical Engineering Based On Lattice Boltzmann Method

There are a wide range of coupled physicochemical processes in the field of geotechnical engineering,such as solid particle fields,seepage fields,temperature fields,and chemical fields.Combined with the characteristics of many mineral elements and random spatial structure,the multi-field coupling process in geotechnical engineering is characterized by cross-scale,nonlinear and non-equilibrium.Therefore,the appropriate calculation method is self-evident for studying the importance of multi-field coupling.Recent studies have shown that the lattice Boltzmann method(LBM)is widely used in various disciplines and simulation of multi-field physicochemical coupling reaction processes in the field.because of its strong coupling ability,high computational stability,and the ability to break the traditional barriers of traditional fluid mechanics(such as the Navier-Stokes equation based fluid mechanics method).Based on the above characteristics of LBM,this paper takes the problems of rock-soil freezing and thawing,debris flow,and dissolution of rock and soil in geotechnical engineering as the background.Based on the previous studies,it is proposed to apply to frozen phase transition and fluid-structure coupling.The LBM model of chemical erosion reaction studied and explored the freezing process of saturated sand,the flow process of particles and the seepage and dissolution process of rock and soil fissures from the mesoscopic depth.The main contributions of this paper are as follows:(1)For the freezing and thawing of rock and soil in geotechnical engineering,by simulating the freezing process of saturated sand with porosity of 0.4,0.45 and 0.5,it is found that the freezing process is affected by both porosity and location,and the whole freezing process can be summarized in.There are three phases: the non-freeze phase,the partial freeze phase,and the full freeze phase.When the location is far away from the cold source,the porosity will dominate the freezing of the saturated sand,otherwise the thermal gradient will dominate itthe freezing of the saturated sand.In the former case,the water blocking effect controls the progress of the entire freeze;in the latter case,the control of the freezing process by the thermal gradient is more pronounced.(2)A large number of studies have shown that continuous fluid-solid coupling methods are difficult to capture the effects of non-uniformity at the particle level,such as force transmission and distribution of force chains.This phenomenon is caused by the microstructure effect,and the LBM-DEM coupling method can simulate these microstructure effects.Aiming at the landslide and debris flow problems in geotechnical engineering,the LBM-DEM method with curvedboundary method YMS model is used to calculate the coupled physical effects of particles and flow fields and to simulate single-particle free-fall motion,single-particle motion in Couette flow,particle sedimentation motion in viscous fluids,and multi-particle slope sliding in viscous fluids were simulated.These simulations capture individual performance at the particle level and contribute to a better understanding of dense particle flow rheology and continuous model limitations.The simulation found that the sliding of the population particles is accompanied by a large number of individual characteristics of surface particle hopping.This phenomenon which is subject to the initial state of the slope,density,fluid viscosity and the spatial distribution of the slope microstructure.(3)For the seepage and erosion of rock and soil in geotechnical engineering,the seepage flow under the influence of many factors such as single fracture in rock and soil,seepage velocity in fracture network,reaction rate,concentration and diffusion intensity,and geotechnical mineral composition are simulated.The dissolution process.Through the dissolution simulation of rock and soil under different flow rates and reaction rates,it is found that the dissolution of minerals exhibits vertical dissolution when the flow rate of the fluid is fast and the reaction coefficient is also large.This is also the case when the flow rate of the fluid is slow and the reaction coefficient is also small.However,when the fluid flow rate is slow and the reaction coefficient is large,it exhibits a horizontal dissolution characteristic.The example simulated in this paper shows that the flow rate is the dominant factor affecting the dissolution rate of rock.Then the effect of insoluble minerals on the dissolution of rock and soil was studied.The analysis found that the main factor determining the maximum flow rate is the minimum mechanical gap width.Rocks in which insoluble minerals grow vertically have a minimum hydraulic gap compared to horizontally grown rocks.The horizontally grown insoluble minerals cause an increase in the growth of vortices in the micropores,causing a decrease in the flow rate of the microchannels.Therefore,the rock that grows vertically insoluble minerals is the first to be dissolved.Finally,the dissolution process of rock mass with and without insoluble minerals is simulated respectively.It is found that the wormhole phenomenon occurs in the dissolution of rock and soil in both cases.However,the rock fissures without insoluble minerals will form a large bias current effect,and the drift effect and the wormhole phenomenon will be promoted and mutually promoted,so the wormhole phenomenon is more obvious.