Jing-Cai Jiang

A Limit Equilibrium Stability Analysis of Slopes with Stabilizing Piles

This paper presents a design method for slopes with a row of piles to enhance slope stability or to prevent slope failure. The basic idea of the method is to allow that two different slip surfaces can be assumed in upslope and downslope earth masses of the row of piles. Contrary to the conventional limit equilibrium procedure where a factor of safety is calculated for a given slip surface, in the present method forces acting on the stabilizing piles are estimated based on a given slip surface whose factor of safety is prescribed to ensure the slope stability. By assuming a slip surface in upper and lower earth masses respectively, the forces acting on the piles can be calculated from an existing limit equilibrium method with a prescribed value of the factor of safety. The Bishop method is employed, and a repeated trial procedure is used to find the most dangerous situation for the piles and the corresponding two critical slip surfaces in the upside and downside of the pile row. It may be understood that if the stabilizing piles are still sound under the most dangerous situation, then the slope will have, at least, the prescribed (target) factor of safety. In the proposed method, we clearly distinguish between forces which piles in a row can bear, i.e. the horizontal bearing capacity as passive piles, and forces which piles in a row should bear under the target factor of safety. The consideration in which the latter does not exceed the former makes possible a more rational design for stabilizing piles. The results of some examples illustrate the effectiveness of the proposed method.

A Comparison of Predicted and Observed Slope Failures Due to the 2004 Niigata-Ken Chuetsu Earthquake

A GIS-based approach for regional assessment of seismic landslide displacements is represented. In this approach, a rigorous Newmark’s analysis extended to a circular failure surface was integrated with a GIS to predict seismically induced slope displacements on the basis of rotation. More precise digital elevation model (DEM) with small size grid cells can be used to generate slope models and to extract the most critical slope section for each cell. In this paper, the proposed method is applied for a regional assessment of landslide displacements due to the 2004 Niigata-Ken Chuetsu Earthquake and the results obtained are compared with the observed slope failures during the earthquake.

DETERMINATION OF SLIP SURFACES IN FRACTURE ZONE LANDSLIDES USING ORIENTED BOREHOLE CORE SAMPLES

In situ and laboratory observation, geophysical measurement and digital imaging analysis of oriented borehole core samples are performed to determine slip surfaces in two large fracture zone landslides in Shikoku, Japan. The following data are obtained from each oriented borehole: (1) a depth distribution of rock quality designation, magnetic susceptibilities, the Equotip hardness values and wet unit weight of core samples, (2) geometric orientation of geologic discontinuities (cracks, joints, faults, etc.), and (3) a depth distribution of numerical color values from digital imaging of borehole core samples. As a result, the rock quality designation, the Equotip hardness value and unit weight, and the orientation of cracks and joints showed a clear change near the slip surfaces respectively, but the digital color values clearly varied only in one of the landslides and no change of magnetic susceptibility of core samples was found at both sites. The results demonstrate that it is capable of locating the slip surface in a fracture zone landslide by using the above-mentioned data in combination.

Numerical simulation of 2D crack growth with frictional contact in brittle materials

In this paper, the extended finite element method (XFEM) is applied in modeling the 2D crack growth with frictional contact under uniaxial compress load in the rock-like materials. First, the implementation of XFEM is incorporated into a commercial FEM software (ABAQUS) in which the constitutive law of linear elasticity and the criterion of maximum tangential stress (MTS) is adopted. Then a user subroutine is coded and incorporated into ABAQUS to simulate the growth of wing crack with the frictional contact in the crack faces. A series of numerical simulations of 2D plane strain rectangle with central pre-set crack are carried out, and computed results are compared with experimental ones. The effects of inclination and coefficient of the friction of the pre-set cracks on growth of wing cracks are examined. In addition, size effect of materials is also investigated, and these jobs contribute to the understanding of 2D crack growth.