Liangqing Wang

Application of back-propagation neural network on bank destruction forecasting for accumulative landslides in the three Gorges Reservoir Region, China

In recent years, a large number of bank destruction occur in the reservoir area under the effect of water fluctuation, which may be lead to reservoir accumulative landslide geological hazards finally. The paper conducted the bank destruction forecasting study for accumulative landslides in the Three Gorges Reservoir Region, China utilizing back-propagation (BP) neural network approach. A representative scenario of Jinle landslide is then taken for analysis purposes. On the basis of the existing data sets of bank destruction cases, the BP neural network forecasting model and the corresponding programs for bank destruction are both presented, whose forecasting result is validated by two independent approaches, namely empirical method and numerical modeling method. Furthermore, the BP neural network model had obvious advantages over the convention approaches in the aspects of the fast calculation speed and high convenience. According to the bank destruction forecasting scale presented above, the corresponding revetment measures can be proposed to prevent the occurring of the bank destruction, whose effectiveness has been further validated by the actual engineering practice.

A Description for Rock Joint Roughness Based on Terrestrial Laser Scanner and Image Analysis.

Shear behavior of rock mass greatly depends upon the rock joint roughness which is generally characterized by anisotropy, scale effect and interval effect. A new index enabling to capture all the three features, namely brightness area percentage (BAP), is presented to express the roughness based on synthetic illumination of a digital terrain model derived from terrestrial laser scanner (TLS). Since only tiny planes facing opposite to shear direction make contribution to resistance during shear failure, therefore these planes are recognized through the image processing technique by taking advantage of the fact that they appear brighter than other ones under the same light source. Comparison with existing roughness indexes and two case studies were illustrated to test the performance of BAP description. The results reveal that the rock joint roughness estimated by the presented description has a good match with existing roughness methods and displays a wider applicability.

A novel method for correcting scanline-observational bias of discontinuity orientation

Scanline observation is known to introduce an angular bias into the probability distribution of orientation in three-dimensional space. In this paper, numerical solutions expressing the functional relationship between the scanline-observational distribution (in one-dimensional space) and the inherent distribution (in three-dimensional space) are derived using probability theory and calculus under the independence hypothesis of dip direction and dip angle. Based on these solutions, a novel method for obtaining the inherent distribution (also for correcting the bias) is proposed, an approach which includes two procedures: 1) Correcting the cumulative probabilities of orientation according to the solutions, and 2) Determining the distribution of the corrected orientations using approximation methods such as the one-sample Kolmogorov-Smirnov test. The inherent distribution corrected by the proposed method can be used for discrete fracture network (DFN) modelling, which is applied to such areas as rockmass stability evaluation, rockmass permeability analysis, rockmass quality calculation and other related fields. To maximize the correction capacity of the proposed method, the observed sample size is suggested through effectiveness tests for different distribution types, dispersions and sample sizes. The performance of the proposed method and the comparison of its correction capacity with existing methods are illustrated with two case studies.

Protection Control Scheme and Evaluation of Effects on Pipeline Crossing beneath Landslide Area

Long-distance natural gas transmission pipelines are planned to pass through the mountain area of midwest China, portions of which are threatened by severe landslide hazards. Therefore, the protection plan and control scheme for pipelines traversing and/or exiting landslide areas are of increasing interest and importance. A typical landslide in western China was used as an example to implement the strategy and evaluate the safety for a typical underground pipeline crossing the landslide area. The investigation and resulting control measures are based on the engineering geological study, and the numerical (finite-difference) interactive model of the pipeline and landslide, including the effect of soil arching. The effect of key design factors, including the spacing of antisliding piles, is determined by three-dimensional finite-difference numerical modeling. This technique also calculates the stability coefficient by use of the strength reduction method and calculation of stress and displacement fields. The results show that the recommended deployment of the antisliding piles can dramatically improve stability by reducing the effect of the landslide, thereby maintaining the displacement and stress of the pipeline within acceptable limits.

Evolution Process of Natural Rock Joint Roughness during Direct Shear Tests

AbstractSurface roughness is one of the most important parameters that have significant influence on the mechanical and hydraulic characteristics of rock joints. To investigate the evolution of surface roughness under normal and shear loads, direct shear tests and numerical modeling based on the discrete-element method (DEM) were performed; bright area percentage (BAP), which places emphasis on the contact areas, was used as an index to describe the roughness. The results demonstrate that the surface roughness of rock joints decreased gradually as the shear displacement increased, and then roughness experienced a significant reduction in the residual stage and remained constant. Furthermore, the evolution of surface roughness was found to depend on the normal stress and shearing direction. Reduction in the degree of joint roughness with high normal loads was lighter than that with lower normal loads, and roughness varied with shear directions. The numerical simulation method proposed in this study has the...

Identification and Mitigation of Error in the Terzaghi Bias Correction for Inhomogeneous Material Discontinuities

Use of the scanline mapping technique in geometric surveys of rock discontinuities can often lead to a bias, in that discontinuities are not always observed when they are at small angles to the scanline. Terzaghi introduced the concept of a blind zone to explain this bias, and developed a widely used procedure to correct for it. Unfortunately, little is known about errors that may occur when the Terzaghi procedure is used outside the blind zone. This paper presents a detailed derivation to show that such errors arise with this application of the Terzaghi procedure. This error was evaluated using simulated orientation data and a case study of the 2008 Wenchuan earthquake (Sichuan, China). The results of these tests yield the optimal values of grid size and sample density for reducing the error.

Optimization-Based Design of Stabilizing Piles

Piles are widely adopted for stabilizing the unstable slopes or active landslides. The subject of stabilizing piles has been extensively studied in literature; however, the optimization of stabilizing piles is rarely reported. This paper presents an optimization-based design framework for landslide stabilizing piles, within which both effectiveness of the stabilizing piles (as reinforcement in the landslide) and cost efficiency could be explicitly considered and optimized. The design parameters of the stabilizing piles considered in this paper include pile diameter, spacing, length and position. The design objective is to simultaneously optimize the reinforcement (i.e., stabilizing piles) effectiveness and cost efficiency. In that the desire to maximize the reinforcement effectiveness and that to maximize the cost efficiency are two conflicting objectives, the outcome of this bi-objective optimization yields a Pareto front which depicts a trade-off between these two design objectives. With the obtained Pareto front, an informed decision regarding the design of landslide stabilizing piles can be reached. The effectiveness and the significance of this optimization-based design framework for landslide stabilizing piles are demonstrated through an illustrative example.

A new framework for characterizing landslide deformation: a case study of the Yu-Kai highway landslide in Guizhou, China

This paper presents a new framework for characterizing landslide deformation. Here, the deformation of a landslide is interpreted as a summation of three components: rigid deformation, within-mass deformation, and residual deformation. On the basis of the monitored data of the landslide deformation, these three components may be characterized separately: the rigid deformation is simulated by a summation of a trend term and a periodic term, the within-mass deformation is simulated by a high-order polynomial model, and the residual deformation is simulated by a conditional random field model. In particular, the characterization of the residual deformation, the third component of the landslide deformation, with the random field allows for a probabilistic assessment of the landslide deformation in the face of geological uncertainties. With the proposed framework, the evolution of landslide deformation in both geometric and time domains may be established, which allows for an assessment of the sliding mechanism of the landslide. Further, evolution in the geometric domain may allow for an assessment of the serviceability of infrastructures in the landslide area. To illustrate this new landslide deformation characterization framework, a case study of the Yu-Kai highway landslide in Guizhou, China is presented, through which the effectiveness of the proposed framework is demonstrated.

Effects of the particle-size distribution on the micro and macro behavior of soils: fractal dimension as an indicator of the spatial variability of a slip zone in a landslide

A field investigation of the Huangtupo landslide in the Three Gorges Reservoir area, China, indicated that the particle-size distribution—characterized by an index termed the fractal dimension—varied along the main sliding direction: the fractal dimension tended to increase in this direction. A preliminary study of the spatial variability of the slip zone based upon the fractal dimension was performed. Remolded soil samples with various fractal dimensions obtained from the Huangtupo landslide were prepared for laboratory testing that was carried out to determine the effect of the fractal dimension on the micro and macro behavior of the soils. The microstructure of each soil sample was determined using scanning electron microscopy, while its macromechanical properties were evaluated via consolidated undrained triaxial tests. The results showed that there were close relationships of the fractal dimension with the microstructure, stress–strain behavior, and shear strength. The test results were also consistent with the results of the field investigation of the Huangtupo landslide. Thus, the fractal dimension can be used as an indicator of the spatial variability of the slip zone of a landslide.

Influence of composite elastic modulus and lateral load pattern on deflection of anti-slide pile head

AbstractThis paper develops a new method to directly determine the composite elastic modulus of the reinforced con- crete cantilever pile rather than adopt theoretical or empirical approaches. On the basis of the theory of material mecha- nism, the load-deflection equation was deduced to create the relationship between the elastic modulus and the ratio of load-deflection. The numerical modelling tests based on ANSYS separation modelling technology were carried out to determine the composite elastic modulus under different reinforcement ratio, concrete strength grade and distribution pat- tern of driving force. The results can be used to create the quantitative relationship between the composite elastic modulus and reinforcement ratio as well as concrete strength grade. Comparison amongst various lateral load pattern were made to show that the deflection of pile head is obviously affected by the lateral load pattern, and the corresponding equations of the deflection of the pile head under different lateral...