Fracture Grouting Mechanism And Experiment Study In Compact Soil Based On Plane-strain Model

As the fast development of cities, the underground space in use is widely spread, and the method of controlling the soil deformation after underground excavation is grouting, which can improve the impermeability of the soil, prevent groundwater flowing into the pit and tunnel, and control the ground settlement. On the other hand, the soil and rock can be reinforced directly by grouting. The method has a wide range of applications in the field of civil engineering, especially the fracture grouting. However, the theory is far behind the level of its application in practical engineering. This paper has summarized the results of previous studies, and my major work is:Firstly, summarize the status of theoretical research of grouting, introduce the commonly used grouting process and types in detail, point out the advantages and disadvantages of different methods of grouting after analyzing and comparing them, and then established the type of research in this paper, that is, fracture grouting mechanism study.Secondly, in taking the premise of plane strain model, this paper designs a fracture grouting system, out of which the development of grouting fluid can be directly observed, this system also overcomes the defect existing in previous experiment that we can only see the grouting fabric after opening the model. In addition, non-contact precision measurement instrument can observe the observation points during the whole experiment, in this way, we can get the displacement path of the observation points.Thirdly, soil samples were compared before and after the grouting test, soil density, water content, shear strength, permeability coefficient and other related physical parameters were analyzed so as to check and verify the fracture grouting for soil reinforcement and improvement of soil impermeability. The size of the grouting bubble, spreading of grouting fluid, the thickness of the grouting fabric, stone rate of grouting fabric were studied and measured, thus we can go deep into the effects of fracture grouting, the theory is also well verified. During the whole experiment, the grouting pressure and grouting volume are recorded in detail, thus we can find out the internal relations between this two factors and the spreading speed of grouting fluid. This paper analyzed and discussed the influence of different soil thickness, different water-cement ratio and other factors on grouting results. Fourthly, some trial-related questions were put forward, aiming at the special phenomenon that happened in the experiment, we give some preliminary analysis and research, which has some explanation and guidance meaning for actual projects.Fifthly, take the use of finite element simulation software FEPGGID to simulate the grouting process, output its soil pore pressure and stress data, use Tecplot360software as post-process to output the data in the form of graphs. Through the study of numerical simulation results, as well as comparing it with the phenomenon and result of indoor grouting test, find out their differences. This paper not only simulate the single-hole grouting, but also the double-hole grouting were simulated, finally, contrast the similarities and differences when under the different conditions.Sixthly, as the theories of temperature and seepage field have high similarity, this paper uses large finite element software ANSYS to simulate the seepage of soil samples, comparing the permeability coefficient and seepage volume under different pressure and grouting fluid shape. Besides, this paper finds the principle of nodal displacement under different load level, calculates and compares the elastic modulus and compression modulus of the soil before and after fracture grouting.