Research On Polymer Grouting Materrial Properties And Directional Fracturing Grouting Mechanism For Dykes And Dams

Aiming at the urgent need of reinforcement engineering in the dykes and dams and the development of the polymer grouting technology, using the non-aqueous reaction type two-component polyurethane foam as the grout material, the directional fracturing grouting technology is developed for anti-seepage reinforcement of dykes and dams on the basis of the systematic study of the material properties in this paper. The main researches are summarized below:(1) According to the characteristics of the two-component non-aqueous reaction type polyurethane foam, specimens grouting molds using in the compression, bending and tensile test and equipment testing the expansion force and permeability of material are developed. A large number of test results of material properties are obtained through the more comprehensive experimental study on the physical and mechanical properties of the two-component polyurethane foam grouting material. A group of curves are established including the largest expansion versus the density, the initial seepage pressure versus the density and the compressive strength, the bending strength and the tensile strength versus the density. The results show that two-component polyurethane foam is a comprehensive excellent grouting material in anti-seepage of dykes and dams.(2) Further studies on the diffusion mechanism of the two-component polyurethane foam polymer material propagation in the soil are carried through a large number of field tests. It reveals that the polymer grouting propagates in soil mainly in a mode of sheet veins and the self-expansion polymer grout is of compaction and penetration cementation to the surrounding soil.(3) Considering the characteristics of polymer injection material diffusion in the soil and the feature of the polymer grouting technology, the method using the polymer directional fracturing grouting in anti-seepage reinforcement of dykes and dams is firstly put forward. At the same time the theoretical formula on the directional fracturing crack propagation pressure and the cracking length is developed. Using the directional fracturing drilling tool developed by self and the directional fracturing method can directionally build a ultra-thin polymer anti-seepage wall about 2 to 3cm thickness which itself has good mechanical and anti-seepage properties and closely bonds with the surrounding soil, forming a composite impervious structure.(4) Based on the rheology, fracture mechanics and rock mechanics theory, a nonlinear finite element cohesive element model is established, and then the directional fracturing mechanism of the polymer grouting is simulated by using the bonding element method. As a result, the directional crack propagation length and opening width with the different grouting volume are obtained, which is basically consistent with the field test results. Thus an efficient method is presented for design in polymer directional fracturing grouting project of the dykes and dams(5) The polymer fracturing grouting prototype test is performed on the homogeneous earth dam. The site excavation results show that the impermeable body thickness, propagation direction, extended range and overlap effects formed in the soil reached expected results using the polymer directional fracturing grouting technique. It just verified correctness of the dam grouting polymer directional fracturing theory and feasibility of the method.