Yan Hui Zhong

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.

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.

Numerical Simulation of the Effects of the Treatment to Rock Tunnel Collapse

Aiming at collapse in the excavation of tunnel in western Henan, the measures including cement grouting and leading conduit are proposed to be used in the treatment of collapse, and the processes of the treatment is numerical simulated. Comprehensive analysis shows that the broken surrounding rock strength has been improved significantly, and it worked fine after being treated.

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.

Research on the Identification Method for Void Location of Semi-Rigid Base Pavement

Using finite element software, the analysis model of semi-rigid base pavement with voids is established. Variation of deflection under load of Falling Weight Deflectometer (FWD) is studied and the reference critical value is obtained to determine whether there are the voids. According to analysis of the deflection basin data under different location, the identification method for the void location of semi-rigid base pavement is established. The field test shows that it is feasible to use this technology in void identification for semi-rigid base pavement.

Application Research of Ground Penetrating Radar Detection on the Metal Structure in Tunnel Lining

As a nondestructive testing technology, GPR has been become one of the most important tools in quality inspection of tunnel lining at present. It is widely applied to tunnel disease detection, such as the holes, cracks, voids between tunnel lining and surrounding rock, and it is also used to determine the steel arch distribution and lining thickness of tunnel. Through the application of GPR in a highway tunnel lining detection, response characteristics of reinforced bar and steel arch frame are analyzed on radar maps under different frequencies of radar. Through identifying abnormal reflection in radar maps and interpreting its reason, the number and arrangement of reinforced bar and steel arch frame can be obtained. Comparing with the tunnel design, good results are obtained.

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.

Method of Analyzing the Size of Voids Beneath Rigid Pavement Slabs

The size of voids beneath rigid pavement slabs is an important factor which influences the bearing capacity of roads. GPR is an advanced method for detecting voids beneath rigid pavement slabs. Combined with drilling and sampling, equations including parameters of GPR wave amplitude, horizontal size and vertical size of voids are established for analyzing the size of voids. Then, based on the equations, the horizontal size and vertical size of voids can be calculated according to the actual GPR wave amplitude.

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.

Experimental Research on the Relationship between Dielectric Constant and Compressive Strength of Cement Concrete Materials

Dielectric constant is the most important material property which ground penetrating radar(GPR) data reflects. Based on experiment, through the determination of the compressive strength during concrete mixture ages and the real part and imaginary part of dielectric constant, the relationship between dielectric constant and the compressive strength of cement concrete material is studied. It is shown from the achievements that there has feasibility to non-destructively test the cement concrete material compressive strength by using GPR.