Research On Diffusion Mechanism And Application Of New Slurryin Bridge And Tunnel Engineering

Soft sandy soil layer can often be encountered in bridge and tunnel engineering construction,which always leads to poor construction quality because of its low intensity.In order to improve the construction performance of sandy soil layer and enhance its intensity,a new slurry material with controlled flowability and permeability is developed which enhances the strength of the sandy soil material by fluidity and permeability of mud in this paper.At the same time providing the design guidance for the practical engineering application of the new mud reinforcement through predicting the diffusion and convective behavior of the mud material in the sandy soil material based on the theory of infiltration grouting.The flow law of mud materials with different constituents is confirmed by the rheological property test equipment.The congelation time of this new mud material in the different conditions of salinity,acidity and alkalinity is measured based on the hardness test method.The shear strength and corresponding law of mixed mud sand materials with different mixing ratio can be obtained in virtue of direct shear apparatus.The diffusion and convective behavior of the mud material in the sandy soil can be explained by the FICK Law and Poiseuille's Flow Theory and the diffusion and convection law of mud materials in sandy soil can also be tested.Meanwhile,by means of the finite element method and analytical method,the slurry diffusion and convection patterns can be calculated and analyzed separately.The comparison between experiment results and the calculating results can verify the theoretical calculation and the effectiveness of the method proposed in this paper.The construction stability of the pile foundation is simulated by the finite element platform ABAQUS and the coupling action of seepage and stress field.A new type of slurry lifting hole wall stability program is adopted to reproduce the actual construction process in the simulation and the new mud diffusion theory put forward in this paper is used during the calculation.The mud diffusion area is defined according to the strength of the equivalent material mixed with mud and sand.In order to arrange a reasonable excavation steps,excavation spacing and support mode plan in the engineering example,the stability of the soil around the excavation area is simulated by the finite element simulation of the single hole drilling model and the double hole excavation model.The mud convection theory proposed in this paper is applied in an underground tunnel with shallow buried expressway.With the pipe roof construction method,the new slurry is injected into the sand of the surrounding rock by grouting pressure,and the strength of sandy soil material is enhanced by the combination of mud and sand.Moreover,the observation of the deposition displacement of surrounding rock area in the whole construction process can be used to examine the improvement of the mud material to the stability of surrounding rock.Furthermore,displacement sensors are used to observe the displacement field of the surrounding area around the tunnel,which in the case of vehicle load for a long time to determine the stability of the soil around the tunnel after grouting reinforcement.Moreover,it also can evaluate the characteristics and advantages of the new mud material in the respect of strengthening the weak area of sand.