Fuming Wang

Experimental Study on the Anti-Permeability Properties of Polymer Grouting Materials

The polyurethane foam as a representative nonaqueous reacted polymer grouting material has become one kind of advanced comprehensive performance material, and therefore it is necessary to research on its anti-permeability properties. According to impermeability grade method, polymer grouting materials are tested under different initial pressures and different densities. The results indicate that the density of polymer materials is generally at the range of 0.1g/cm3～0.3g/cm3 and the initial seepage pressure is at the range of 0.3～0.7MPa, which can bear 30 to 70 meters head pressure when seepage grouting is carried out in hydraulic engineering. According to the actual needs of different projects, polymer grouting amount is controlled to regulate the density of polymer materials to meet the need of different projects impermeability.

Numerical and Experimental Studies of Diffusion Law of Grouting with Expansible Polymer

AbstractPolyurethane has been widely used as new chemical grouting material. Expansion characteristics caused by chemical reactions make polymer grout different from other types of grout. To throw ...

Identification of Surrounding Rock Parameters Based on MSVR

An inversion method based on multi-output support vector regression (MSVR) is proposed for identifying the mechanical parameters of surrounding rock. This method considers the surrounding rock as a multi-output system during excavation, and the surveyed rock deformations of each monitoring section as its output. First, perform numerical experiments based on the principle of orthogonal test to obtain the calculated deformation values corresponding to different rock parameter combinations, and use them as the samples for training the model of MSVR as reflecting the nonlinear mapping relationship between rock and its deformations. Second, use the PSO to seek the optimal rock parameters based on measured deformations of rock mass. An example is employed to test the presented inversion method. The results showed that compared with the inversion method based on single-output support vector regression (SSVR), the proposed one is more inclined to reach the global optimization goals and achieve more reliable inversion results due to its consideration of the inherent correlativity among the measured deformations of each monitoring section.

Reinforcement Experiment of a Hollow Slab Bridge by External Prestressing

Simply supported hollow slab bridge is widely used in highway network of China. Under overload vehicles, the concrete hinges of such bride are easily damaged, which usually causes single slab bearing and tremendously reduces the bridge’s load capacity. It is necessary to take some reinforcement measures to enhance the carrying capacity of such impaired bridge for traffic safety. In this paper, a field reinforcement experiment of an actual hollow slab bridge, which has experienced a destructive test with its transverse connections seriously damaged, was performed by applying external transverse and longitudinal prestress to it. The strengthening scheme adopted in this experiment was detailed. By means of static truck load test, the variation of deflections of the bridge before and after strengthening was obtained. The test results showed that the proposed strengthening method can effectively enhance the damaged hollow slab bridge’s transverse stiffness and improve its bearing capacity.

Modulus Back Analysis of Pavement Structure Based on PSO

A method for modulus back analysis of pavement structure based on particle swarm optimization (PSO) is presented. The principle and implementation process of the method is detailed. Some theoretical and experimental data of pavement deflection are selected to test its performance. The contrastive analysis of the modulus inversion results of the proposed method and some representative pavement modulus back calculation softwares using the same deflection data is also performed. The results show that the presented method has relatively high identification accuracy and notably computational stability, which can effectively reduces the influence of initial tentative value on inversion results of pevement modulus.

Evolutionary Structural Shape Optimization Based on Adaptive FEM and Boundary Representation of B-Spline

This paper presents a structural shape optimization algorithm based on the evolutionary structural optimization (ESO) method in conjunction with element error estimate and adaptive FEM. B-splines are used to describe the boundary of the design domain; the shape of these B-splines is governed by a set of master nodes which can be taken as the design variables. The optimal shape of the design boundary with constant stress is achieved iteratively by the movement and update of the position of the master nodes based on nodal stress leveling. The result quality, in terms of accuracy and efficiency, is tested and discussed with an analytical solution.

Method for Identifying the Depth of Voids beneath Rigid Pavement Slabs Based on GPR

According to radar wave propagation characteristics in pavement structures, the impacts of depth of multiform voids upon radar reflected signals are studied by establishing the model of Ground Penetrating Radar (GPR) electromagnetic wave propagation in rigid pavement with voids. Meanwhile, the method of determining the depth of voids beneath rigid pavement slabs is presented. This paper provides an important technical support for identifying the depth of voids beneath slabs in rigid pavement based on the GPR reflected signals.

Numerical Simulation of GPR Electromagnetic Wave Propagation in Rigid Pavement with Voids Based on FDTD

Two-dimension finite difference time domain (FDTD) update equations are established, and the GPR electromagnetic wave propagation in rigid pavement with voids beneath slabs is numerical simulated by using effective CPML boundary conditions, and then the two-Dimension GPR images for voids beneath slab are obtained. Moreover, the relationship between characteristics of voids beneath rigid slabs and GPR data is analyzed. The achievements of this paper will provide a theoretical basis for the use of GPR to rapidly detect voids beneath rigid slab.

Inverse Analysis of Surrounding Rock Mechanical Parameters Based on LS-SVM

Inverse analysis is regarded as an ideal way to achieve the mechanical parameters of rock mass using in situ measured deformation data of surrounding rock during the construction of underground engineering. Aiming at the disadvantage of high computational complexity when identifying mechanical parameters of surrounding rock by employing the inverse method based on standard support vector machine (Vapnik’s SVM), a new back analysis method based on least squares support vector machine (LS-SVM) was presented. The basic principle of the method was introduced. An example was adopted to investigate the practicality and reliability of the method, and the calculation results indicated that, compared with the inversion method based on standard SVM, the method proposed in this paper possesses higher calculation efficiency and inversion precision.

Strengthening Experiment of a Hollow Slab Bridge by External Transverse Prestressing

For hollow slab bridge, its concrete hinge joint is prone to be damaged under overload vehicles, as weakens the transverse integrity of bridge, leads to single slab bearing and threatens the safety of service. Aiming at the problem, a strengthening experiment of an actual concrete hollow slab bridge, which has experienced a destructive test with its transverse connections seriously damaged, was performed by applying external transverse prestressing to it. The strengthening design and construction technology of external prestressing were introduced. By means of truck static load test, the variation of deflections and strains of the bridge before and after strengthening under different tension force was obtained, and the influence of tension value to strengthening effect was emphatically analyzed. The test results proved the effectiveness of the strengthening method and some improvement suggestions were also presented.