No abstract

The assessment of settlement deformation of engineered structures under high-speed railway tracks is an important control link in high-speed railway line construction. This paper discusses characteristics of settlement deformation of sections of subgrade, bridges and tunnels, and analyzes the suitability of predictive methods in currently available technical codes and standards based on measured data of settlement deformation. Currently available assessment analysis methods have good applicability for subgrade sections but are not suitable for sections of bridges and tunnels. Suitable assessment analysis methods are proposed and have been successfully applied to settlement deformation of engineered structures under the tracks of high-speed railway lines. The methods suit the characteristics of “small magnitude and large fluctuation” changes of measured settlement deformations taking account of the construction process of the engineered project.

As for stabilizing piles used to reinforce landslides, landslide thrust acts on their upslope sides but slope resistance acts on their downslope sides at the same time. In fact, the results that the former subtracts the latter are effective loads on piles, which can be called residual thrust on piles. The interaction between pile and rock or soil mass is simulated by elastoplastic finite element method in the paper. And the effect of slide mass and pile stiffness on residual thrust on stabilizing piles is analyzed. The results show that residual thrust on a stabilizing pile become more and more with elastic modulus of slide mass or the pile being increased. Meanwhile, action point of the resultant of residual thrust on the pile is lower and lower with elastic modulus of slide mass being increased but it is higher and higher to some extent with elastic modulus of the pile being increased. These results can be of theoretical reference for comparison and selection of various design plans of stabilizing piles.

Near-field ground shock features are analyzed according to the seismological record of the May 12 Wenchuan earthquake made at the Wolong observation station. A numerical analysis model is established by taking the record as the input seismic load and a real high and steep rock slope on the bank of the Zipingpu Reservoir. The acceleration response and shear strain increment distribution features at different locations of the slope under horizontal seismic force are analyzed using Plaxis software. The moment when the widest plastic zone occurs for the slope is obtained by time history analysis. The corresponding stability factor of the slope at that moment is calculated using the strength reduction method (including shear strength and tensile strength). The above is the Time History Analysis–Strength Reduction Method presented in this article. In addition, the stability factor of the slope can be calculated using the pseudostatic method by taking the seismic force as the external load. This is the Time History Analysis–Pseudostatic method put forward in this paper. Analysis results demonstrate that, as far as the studied high and steep slope is concerned, at 31.89 s, the stability factor calculated with the Time History Analysis–Strength Reduction Method is 1.004, which is slightly larger than the 0.833 obtained using the Time History Analysis–Pseudostatic Method (Spencer method). Both results demonstrate that there is collapse and sliding failure of the localized rock mass at the top of the slope at that moment because of joint fracture. Field investigation after the earthquake further verified the calculation result, proving to a certain degree the rationality of the analysis method presented.

On the basis of seismic wave recorded by Wolong Measuring Station in Wenchuan Earthquake occurred on May 12, 2008, and taking a high rock slope (about 1397m in height) at the bank of Zipingpu Reservoir as the specific example, analyses have been made, with Plaxis dynamical simulation analysis program, on characteristics of influence upon acceleration time history, shear strain distribution, principal stresses distribution and stability of high rock slope by original seismic wave, and seismic wave with frequency expanded by 1.5, 2 and 3 times, respectively. Results of the analyses demonstrate that dynamic response characteristics of the slope top are notably influenced by multiplication factor of seismic wave frequency. As far as the real slope in this article is concerned, it generally presents a gradual decrease of PGA of the top of high rock slope, reduction of slope body shear strain and a corresponding drop of dynamic response of slope body as a whole, with the increase of seismic wave frequency.