Yan Shuwang

Finite-element modelling of soil-geogrid interaction dealing with the pullout behaviour of geogrids

A two dimensional plane-stress finite-element type of analysis is presented to predict the behaviour of geogrids embedded in sand under pullout loading conditions. In the analysis the interactions between soil and geogrid are simulated by non-linear springs. The stiffnesses of the springs can be determined from simple tests in a specially designed pullout box. The proposed finite element (FE) analysis is applied to interpret test results from a large scale pullout test rig. The predicted behaviour of the geogrid under pullout load agrees well with the observed data including the load-displacement properties, the displacement distribution along the longitudinal direction and the mobilisation of the frictional and bearing resistance.

Analysis of dry dock slope stability at different construction stages

Through constructing to refilling the dry dock for the tunnel cross Haihe River in Tianjin Binhai New Area, the slope of the dock will be undergoing three stages, i.e., excavation, water filling and water draining, respectively. The stability of the dry dock slope is studied by using Fellenius method of slices and Bishop simplified method. At the excavation stage, the soil disturbance is considered; at the water filling stage, the capillarity suction lost above the phreatic line is considered; and at the water draining stage, the slope surface is assumed to be the phreatic line, the sudden falling of the water level is considered and the effective stress method is used. The research result has been adopted as the theoretical basis for the design of the project.

An FE analysis of reinforced subgrade under automobile loading

An FE analysis procedure was presented to predict the behavior of soil-geogrid interaction under automobile loading. The dynamic interactions between the transverse bars, the longitudinal ribs and the soil were simulated by a system consisting of nonlinear springs, dashpots and masses, to study the deformation properties of the reinforced soil. The equivalent stiffness and damping ratios could be determined with the shaking table. The dynamic responses of a reinforce subgrade were analyzed with the 3D finite element approach. This approach is programmed and applied to analyze the soil-geogrid interaction under dynamic loading. The comparative analysis of the response of the reinforced subgrade and that of the subgrade without reinforcement shows that the geogrid placed at the bottom of the base layer may effectively reduce the accumulative plastic deformation due to the cyclic automobile loading.

Model Test Study on Dredge Slurry Vacuum Preloading

Dredge materials with the water content more than 80% have been used for land reclamation in Tianjin, China. The dredge is transferred by pipeline to the reclamation place and then strengthened with the vacuum preloading technique. It has been found that with the thickness of the filled dredge layer becomes larger and larger, the quality of soil improvement is not as good as expected. Field investigation shows that after vacuum preloading the vane test strength can reach 50kPa at the ground surface, but decreases along with depth dramatically. The model test is carried out to detect the factors that may influence the efficiency of using vacuum preloading to improve dredge soil foundation.

Research on settlement and wavy failure of road on very soft soil foundation

Soil foundation in Tianjin Harbor is formed by hydraulic filled materials strengthened by vacuum preloading method, which is still with lower strength and larger compressibility. Large settlement and wavy failure of the roads constructed on such soil foundation are often take place after two or three years after construction, because of the heavy vehicles running on the roads with high frequency. In order to deal with the existing problems of constructing roads on such very soft clay, the following work is carried out: the displacement characteristics of roads constructed on very soft soil foundation are identified; the design methodology of constructing roads on very soft soil foundation is discussed; the settlement of the constructed roads is calculated with FE methods and the mechanism of wavy failure of the roads on very soft soil foundation is analyzed.

Shear strength finite element investigation of concrete beams with proposed horizontal shear reinforcements in webs

In this paper, the horizontal web reinforcement is proposed as shear reinforcement along the depth of the beam according to oblique section shear mechanism and analyze its shear performance using the finite element software ANSYS. The research shows that the horizontal web reinforcements can carry the horizontal component of the principal tension stress and stirrups carry the vertical component. The horizontal web reinforcements and stirrups together form the integrated shear model to limit the diagonal cracks development as well as reduce the width of diagonal cracks. It proposed the formula of calculating width of diagonal cracks in conjunction with finite element results.