Dynamic Compaction Of Foundation Reinforcement Design Parameters

On the theory of dynamic consolidation Foundation scholars at home and abroad have done a lot of research, Hut so far failed to reach maturity and sound theory, based mainly on experience and on the spot test. Theory and methods, Wave Theory (analysis) can not consider the complex dynamic nature of soil (non-uniform nature of the non-linear). boundary conditions (contact stress) difficult to establish; Sikete (Scott) formula does not apply to multi-layered foundation, soil compression modulus of the impact is difficult to dotermine, and the formula itself, there are some problems; finite element method. Difference law numeric method of workload, it is not appropriate to design units and the construction of application; Boundary Element Method is not easy to deal with the nonlinear and non-homogeneous soil characteristics. Dynamic Compaction impact dynamic nature of the soil is more complex and dynamic in general, the static model does not apply. Under the existing test results, soil under the impact of the dynamic modulus and soil porosity, self-stress, loading time and the other hits. at the micro-cracks appeared tamping soil infiltration Er Shi traditional rules no longer fit. Make reasonably accurate theoretical calculation results, it must first load the impact on soil properties have a better understanding. So the theory of dynamic compaction method it is necessary to conduct thorough study and discussion.Path analysis of the normal techniques of practical engineering problems is the first question the assumption that certain probability, be mechanical model Second, using mathematical language (ie mathematical equation) to describe the mechanism of its effect, the mathematical model has been the problem, By using mathematical models to calculate the appropriate solution. Therefore, the calculation of the theoretical results close to the real state, Much depends upon the issue of the mathematical model can accurately reflect the nature and mechanism of the phenomenon.An abstract mathematical model to two million by : 1. Basic equations 2. Boundary conditions : a.. B. role in the region. Parameters;c. Load expert system. Wpe boundary conditions. InitialConditionsFor practical problems with a different reason for the researchers is to be different and even divergent results. was established by the mathematical model to two million of the difference. So how practical problems abstract equations and the appropriate boundary conditions is the key to the analysis of this issue. Dynamic consolidation of the theoretical foundation of this project in terms of practical problems. Currently the main driving force for consolidation theory saturated soft clay and sandy soil against impact damage theory in the corresponding mathematical models, the main issues of principle are :Basic equations : 1. Model 2 — what stress-strain relationship. Displacement Model 3─ what strain relations. The study is only soil skeleton, or by coupling analysis and consideration of soil matrix pore water (that is dynamic consolidation model) 4. Foundation is continuous or discrete model model boundary conditions : 1. Dynamic compaction method foundation calculated the effective range (defined role in the region) 2. Load transient simulation of the dynamic compaction 3. At the bottom of tamping rammer dynamic contact with the ground surface stressCurrently, there are various theories and the study of dynamic compaction method, The main difference is in the handling of the above principle. — On the stress-strain relationship, broader use of Hohai University Professor Qian Jiahuan [1] proposed a model of the dynamic compaction loading bilinear. — Displacement in the contingency relations, most researchers still use the "small strain" to assume that Jiang Pang foundation in the literature [2] that in the course of tamping rigid displacement of a large part of the displacement, proposed the use of "deformation" assumption that the geometrical nonlinearity, which would be more in line with reality, especially for the first down, and sometimes displace up to 1m above. Found not in the literature, mainly on the soil for dynamic analysis; [5-8] In literature, comprehensive analysis of the interaction of soil and water, the establishment of the pore water percolation model of dynamic consolidation. Based on the literature [for the establishment of a simplified model of one-dimensional wave equation, the dispersion model, [10] The main boundary element method, dynamic finite element [11], [12] and other dynamic finite element numerical method. Load transient simulation of the dynamic compaction. Experience usually be simplified as a triangle or half - sine wave [13]. Rammer and ground surface at the bottom of the dynamic contact stress calculation of the literature [14] first proposed a formula However, the formula is no longer satisfied with the initial conditions; [15-16] were revised its literature; First presented in the literature [17] calculated using pulse units dynamic contact stress; Literature [18] and integral transformation of the transfer matrix method for the dynamic contact stress; consider tamping rammer which may arise in the spring and repeated contact and separation process, the literature [2. 19] proposed the use of impact — dynamic contact model dynamic contact stress. Based on the theoretical foundation dynamic consolidation, consideration of the merits of all, the following two methods : 1. Dynamic compaction method for dynamic consolidation of the foundations of three-dimensional finite element analysis using generalized assumptions and the model are : ①stress-strain relationship — use dynamic compaction loading bilinear constitutive model; ② strain displacement useing small deformation assumption.③soil for heterogeneous porous media, Biol consolidation to meet the three-dimensional equations; ④ soil permeability coefficient different from the horizontal and vertical directions; ⑤ 3D finite element; (6) simplified half sine wave transient loads, and to consider self-rammer;⑦ unit impulse calculated contact stress;⑧ foundation consider the force of inertia. This is a fundamental difference between the literature [2], the article did not consider the inertia force, that the foundations of tamping quasi-static process at the end of the static finite element equations, So instead of the strict sense of the dynamic model. 2. Based on the geometric nonlinear dynamic consolidation of the foundations of numerical analysis using generalized assumptions and model : ① stress-strain relationship — use dynamic compaction loading bilinear constitutive model; Second, the assumption that large deformation strain — displacement; ③ study of soil, pore water; ④ used axisymmetric finite element; (5) simplified half sine wave transient loads, and to consider self-rammer; (6) foundations of inertia.