Advanced Materials Research Vols. 261-263

Abstract: Different landslide analysis methods were compared in this paper, and the analysis method of levee project seismic landslide risk probability was established based on Morgenstern-Price and Monte Carlo methods, and then the landslide risk assessment standards were developed. The result shows that liquefaction can lead soil layer strength reduction, and will trigger and accelerate landslide, therefore, the impact of soil liquefaction must be reasonably considered in levee and dam seismic stability analysis.

Abstract: The stress field monitor and rheological analysis have been done during excavation. The field monitoring data are compared with numerical simulation results. The result shows: Rock stress variation is influenced by both spatial effect and time effect; when the distance from monitoring section to tunnel face is less than a tunnel diameter, the surrounding rock stress is mainly affected by spatial effect and changes violently; when the distance is more than a tunnel diameter, the surround rock presents rheological properties and stress changes smoothly and continuously. Analyzing the monitoring data and fitting by Poynting-Thomson three-parameter rheological model, we can get the radial stress variation equation with time and predict the final variation value. The final value and numerical simulation results are in comparative agreement.

Abstract: The belled wedge pile, which can improves the friction of pile shaft, tip resistance and reduce the influence of negative skin friction, is introduced. In this paper, the accuracy of FLAC^3D model is verified with field load test results. Subsequently, the numerical model was used to study the compressive behavior of belled wedge pile, conventional belled pile, wedge pile, and uniform section pile with the same concrete volume. Furthermore, the compressive behavior of belled wedge pile group was studied in terms of influencing factors such as pile spacing, stiffness of soil at the pile end, and diameter of enlarged pile head. The numerical results show that the compressive advantages of belled wedge pile can be developed adequately when the distributions of the friction of pile shaft and pile tip resistance are equilibrium, and it increases with increasing pile spacing, increasing stiffness of soil at the pile end, and increasing diameter of the enlarged pile head.

Abstract: As there are more and more high-rise buildings in the big cities, some new foundation pits are usually near old high-rise construction. In this case, foundation pit excavation is an engineering problem which needs to be solved urgently. This paper aims at the problem where the new foundation pit is closing to a high-rise building with a cement fly-ash grave (CFG) composite foundation, though cantilever retaining pile model test, simulate the excavate process, and make a testing system to measure datum in order to research on the characteristics of the earth pressure.

Abstract: The test of soil water characteristic curve (SWCC) and its mathematic model are present. The SWCC can describe the relationship between unsaturated soil matric suction and water content. Matric suction is an important parameter to address when studying the engineering properties of unsaturated soil. And while the measurement of substrate attraction is a very difficult issue, it is also one of the biggest obstacles in the engineering applications of unsaturated soil. By analyzing and researching the test data of SWCC researchers can initially establish the mathematic model which is the SWCC equation. The Van Genuchten model and the Fredlund and Xing model were used to simulate better the changes between the volume water content and the matric suction. Predictions were compared with experimental results to determine the simulation capability of the model for the soil of Beijing.

Abstract: In order to study influences of different load at pile top on the behaviors of negative skin friction piles, field tests of negative skin friction behaviors of three identical piles with different loads at pile top are made in the same site. According to the field test condition, the corresponding numerical simulations are accomplished. The comparison shows that numerical simulation results and field test results in accordance well. The additional settlement induced by negative skin friction is bigger and the neutral position is higher, the additional axial force induced by negative skin friction reduces obviously in piles with pile head load compared with that in piles without pile head load induced by negative skin friction. Along with load increase, the additional settlement increases, the neutral point position becomes higher; the additional axial force reduces obviously. The result indicates there is regularity about the influences of pile head load on negative skin friction. It may be useful to the research for negative skin friction behaviors of pile.

Abstract: In order to avoid heavy casualties and economic losses, and to get an insight into flow state evolution laws of water inflow and inrush in course of tunnel excavation, simulations were done with COMSOL Multiphysics. By coupling and linking different kinds of sub domain governing equations with boundary conditions and possibly initial conditions, three kinds of water flow state, Darcy’s law for water flow in the limestone aquifer, Brinkman equations for fast fluid in the karst conduit; and incompressible Navier-Stokes equations for freely moving of water in the excavated tunnel, are interacted and coupled with each other. Water pressure and velocity were studied and analyzed in course of tunnel excavation. It is proved that there will be no disastrous water inrush when the seepage deformation of the karst conduit is small, and that it is of vital importance to protect and support the clastic medium of karst conduit, and to strictly guard against any change of the permeability of the karst fillings.

Abstract: The FEM mehods for simulating the penetration of jacked pile were summarized. Using the displacement penetration method, the complete uninterrupted penetrating process of jacked pile was simulated with the finite element method based on ANSYS. The soil’s displacement and stress field were obtained, and compared with the field test. The elastoplastic constitution law, large deformation, soil’s gravity field and pile-soil friction contact were taken into account. The difficulties and skills in the simulation were indicated, so it might be helpful to the other researchers.

Abstract: Shallow multi-arch tunnel under unsymmetrical pressure has complex mechanical behavior to which further study is lacking at present. The existing design methods are thoughtless about the features of shallow and partial pressure. The phenomena of cracks, collapse or other diseases in tunnel lining structure are often seen during the construction or after the completion. Combining one tunnel example, this paper presented scientific feedback design method that suited for Shallow multi-arch tunnel under unsymmetrical pressure: made load back analysis with collected information during construction, then averaged the above load and field monitoring load to make forward analysis and internal force calculation, which was used as reference of reinforcement and sectional design for lining structure.

Abstract: This article in a typical road slope model as an example, through large-scale general-purpose finite element simulation software ANSYS/LS-DYNA rockfall on the slope of the roadbed impact for three-dimensional dynamic analysis in the roadbed, slope geological parameters and falling stone initial state is not at the same time on the roadbed impact the results of comparative analysis. The result is the mountain slope of the road construction project provides reference.