Changdong Li

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.

Stability of Huangtupo Riverside Slumping Mass II# under Water Level Fluctuation of Three Gorges Reservoir

After the normal operation of the Three Gorges Reservoir, the water level of the reservoir will fluctuate periodically. Water level fluctuation will soften the rock and soil on the banks, induce underground water fluctuation and decrease the shear strength of rock soil on the banks, and in turn affect the landslide stability. The Huangtupo (黄土坡) landslide is a typical large and complex landslide in the Three Gorges Reservoir region. In particular, the stability of its riverside slumping mass has a great stake. On the basis of the analysis of engineering geological condition and formation mechanism of the Huangtupo landslide, the authors established the 2D finite element model of riverside slumping mass II# and selected proper mechanical parameters of the rock. With the GeoStudio software, according to the reservoir running curve, the simulation on coupling effect of seepage field and stress field was conducted in 7 different modes in a year. The results showed that: ➀ Huangtupo landslide is a large and complex landslide composed of multiple slumping masses, which occurred at different phases. Before reservoir impoundment, it was stable; ➁ it is quite difficult for riverside slumping mass I# and II# to slide as a whole; ➂ the stability coefficient of riverside slumping mass II# changes with the reservoir water level fluctuations. The minimum stability coefficient occurs 48 days after the water level starts to fall and the moment when the water level falls by 11.9 m. Landslide monitoring result is consistent with the numerical simulation result, which shows that although the reservoir water level fluctuation will affect the foreside stability of the landslide and induce gradual damage, the riverside slumping mass II# is stable as a whole.

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.

Design and Testing of a Flexible Inclinometer Probe for Model Tests of Landslide Deep Displacement Measurement

The physical model test of landslides is important for studying landslide structural damage, and parameter measurement is key in this process. To meet the measurement requirements for deep displacement in landslide physical models, an automatic flexible inclinometer probe with good coupling and large deformation capacity was designed. The flexible inclinometer probe consists of several gravity acceleration sensing units that are protected and positioned by silicon encapsulation, all the units are connected to a 485-comunication bus. By sensing the two-axis tilt angle, the direction and magnitude of the displacement for a measurement unit can be calculated, then the overall displacement is accumulated according to all units, integrated from bottom to top in turn. In the conversion from angle to displacement, two spline interpolation methods are introduced to correct and resample the data; one is to interpolate the displacement after conversion, and the other is to interpolate the angle before conversion; compared with the result read from checkered paper, the latter is proved to have a better effect, with an additional condition that the displacement curve move up half the length of the unit. The flexible inclinometer is verified with respect to its principle and arrangement by a laboratory physical model test, and the test results are highly consistent with the actual deformation of the landslide model.

Development and Application of In Situ Plate-Loading Test Apparatus for Landslide-Stabilizing Pile Holes

The horizontal foundation coefficient of pile hole walls is a key factor in the design and maintenance of stabilizing piles. An automatic bearing plate-loading test apparatus was developed to measure the horizontal foundation coefficient of a pile hole wall based on an in situ test. The apparatus has an integral structure, providing two switchable loading modes, i.e., a displacement-control mode and loading-control mode, and all functional parts are integrated into a removable unit. The loading frame is controlled by a proportion integration differentiation closed-loop controller, and its rigidity compensation is considered if a transmission column is used for the large span. The process of the field test is described, including the selection of the test location, preparation of the test hole and operation of the test apparatus. The corresponding relationships between the displacement-foundation coefficient (S-K) curves and the deformation and failure stages of the rock mass during the test are analysed. The accuracy of the test results is assessed via comparison with the corresponding rock layer in the current specification.

Mechanical Analysis and Control Strategy of Pipeline beneath Landslide Area under Different Crossing Angles

Long-distance natural gas transmission pipelines are designed to cross the large-scale mountain area with the start of the West-East Gas Pipeline Project in China. A great portion of the pipelines are now threatened by severe landslide hazards. The pipeline could fail resulting in a great loss because of the landslide failure deformation. Therefore, the spatial arrangement plan of pipeline underground crossing landslide area is one of the key problems. The paper presents a new mechanical model of pipeline and landslide under trapezoidal landslide force to conduct the mechanical analysis on deformation of pipeline. A series of shear force, bending moment and defection of pipeline under landslide with different crossing angle can be deduced according the simplified model presented. Based on a case study of a typical landslide with pipeline underground crossing, the geological mechanical model of landslide and pipeline system can be established. The mechanical characteristics of pipeline can be conducted under the driving force of landslide by utilizing mechanics theory so as to determine the position of maximum stress point along the pipeline. Consequently, the optimal crossing depth and orientation of pipeline can be obtained. The result shows that the proper setting of crossing angle and buried depth can effectively improve the safety of pipelines. The corresponding control strategy suggestions for similar pipeline projects are proposed as well.

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.

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...

Influence of Buried Depth and Non-Uniformly Distributed Driving Force on Stress Characteristics of Pipelines in Landslide Regions

Choosing the reasonable depths of a buried pipeline is one of the crucial issues for long-distance gas transmission pipelines. This paper focuses on the mechanical analysis of a pipeline with a different buried depth under the driving force of a landslide. The relationship between the bending moment, shear force, displacement and buried depth of pipeline can be derived under certain assumed conditions. The result of the Zhong County-Wuhan City gas transmission pipeline project shows that the moment reaches a greater value at the junction and the midsection of the pipeline and the shear force reach maximum at the junction along with the increase of buried depth of the pipeline. On the basis of the stress characteristics of deep-buried pipeline in engineering practice, it can improve the safety of a gas transmission pipeline by enhancing the piping material performance at the junction and the middle part of the pipeline.