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Stabilizing piles are extensively used as an effective landslide control treatment, and the soil arching effect is the key element for the performance of the pile system. Most previous studies on soil arching effect and its application in stabilizing piles were conducted with laboratory tests and numerical simulations, while limited efforts have been dedicated to the analytical characterization of such a soil-structure interaction. In this paper, a new stress-reduction model for soil arch in landslides is established by theoretical derivation. Our model calculation has demonstrated an exponential reduction in the stress along the direction of slipping between and behind stabilizing piles and thus justifies the observations of laboratory tests and numerical simulations. Thereafter, the analytical solutions to the two key arch shape parameters, namely the inclination angle at the foothold and the thickness of soil arch, are derived based on the proposed stress-reduction model. Then, the ultimate bearing capacity of soil arch between and behind stabilizing piles is subsequently calculated, and a three-level load sharing model for landslides is thus proposed based on the stress-reduction mode. The load sharing model can well capture the stage characteristics of the interaction between landslide mass and stabilizing piles. Finally, the calculation model of spacing between stabilizing piles is established based on the proposed stress-reduction model, and it turns to be good in field application. The findings of this study can contribute to a better understanding of the soil arching effect as well as a better design of the stabilizing piles.

Discontinuities have huge impact on civil and mining engineering. To understand the spatial features of discontinuities, it is common to group them into different sets based on orientation. In this paper, a new algorithm is introduced for the identification of discontinuity sets. The new algorithm is developed by combined fuzzy C-means algorithm with variable length string genetic algorithm. In the new method, the number of discontinuity sets is not the necessary input parameter any more. This method is robust, global optimal and totally automatic. To verify its validity, the new method was firstly applied to an artificial data as well as a published data. For artificial data set, the assignment error rate is only 7.4%. For published data set, only 2 discontinuities are assigned to wrong sets. The results indicate that the new algorithm is better than fuzzy C-means algorithm and comparable with other common methods. Afterwards, the new method was utilized to analyze the orientation data sampled at an underground storage cavern site. The new method determines that the ideal number of sets is 3. The new method provided satisfactory results, which confirm its effectiveness and convenience.

In this study, the cluster analysis (CA), probabilistic methods, and artificial neural networks (ANNs) are used to predict landslide susceptibility. The Geographic Information System (GIS) is used as the basic tool for spatial data management. CA is applied to select non-landslide dataset for later analysis. A probabilistic method is suggested to calculate the rating of the relative importance of each class belonging to each conditional factor. ANN is applied to calculate the weight (i.e., relative importance) of each factor. Using the ratings and the weights, it is proposed to calculate the landslide susceptibility index (LSI) for each pixel in the study area. The obtained LSI values can then be used to construct the landslide susceptibility map. The aforementioned proposed method was applied to the Longfeng town, a landslide-prone area in Hubei province, China. The following eight conditional factors were selected: lithology, slope angle, distance to stream/reservoir, distance to road, stream power index (SPI), altitude, curvature, and slope aspect. To assess the conditional factor effects, the weights were calculated for four cases, using 8 factors, 6 factors, 5 factors, and 4 factors, respectively. Then, the results of the landslide susceptibility analysis for these four cases, with and without weighting, were obtained. To validate the process, the receiver operating characteristics (ROC) curve and the area under the curve (AUC) were applied. In addition, the results were compared with the existing landslide locations. The validation results showed good agreement between the existing landslides and the computed susceptibility maps. The results with weighting were found to be better than that without weighting. The best accuracy was obtained for the case with 5 conditional factors with weighting.

This study validated the robust performances of the recently proposed comprehensive landslide susceptibility index model (CLSI) for landslide susceptibility mapping (LSM) by comparing it to the logistic regression (LR) and the analytical hierarchy process information value (AHPIV) model. Zhushan County in China, with 373 landslides identified, was used as the study area. Eight conditioning factors (lithology, slope structure, slope angle, altitude, distance to river, stream power index, slope length, distance to road) were acquired from digital elevation models (DEMs), field survey, remote sensing imagery, and government documentary data. Results indicate that the CLSI model has the highest accuracy and the best classification ability, although all three models can produce reasonable landslide susceptibility (LS) maps. The robust performance of the CLSI model is due to its weight determination by a back-propagation neural network (BPNN), which successfully captures the nonlinear relationship between landslide occurrence and the conditioning factors.

For deep-seated landslides, thermal pressurization in shear zone has been considered an important cause of high-speed collapse. To quantify this mechanism, this study proposed a quasi two-dimensional friction-thermo-hydro-mechanical (FTHM) model, concerning the mechanisms of material frictional softening and thermo-hydro-mechanical softening during the start-up phase of high-speed landslides. In this model, the intact slide mass was divided into a lot of small slide blocks. The dynamic equations of each block, and the heat equations, pore pressure equations of each shear band were established respectively. The model fully considered the morphological characteristics of landslides, and variables such as velocity, temperature, excess pore pressure varied along both the normal and the tangential direction of the whole shear band during the slide mass movement. The model was applied to back-analyze the Vaiont landslide and the results were compared with existing one-dimensional models. It can be concluded that the irregular spatial shape of slide mass makes a difference on mechanism of thermo-hydro-mechanical softening which promotes the collapse, and that the quasi two-dimensional model is valid.

A geostatistical back analysis is developed, which can map spatially distributed Young's modulus (E′), cohesion (c′), and internal friction angle (ϕ′) in a rock mass by fusion of the observed displacement data from the excavation of an unlined rock cavern. It is tested and validated using numerical experiments with a synthetic heterogeneous rock mass, created with field observed spatial variability. Results of the experiments show that this approach yields unbiased estimates of E′, c′, and ϕ′ fields and quantifies their uncertainty. Further, the estimated fields predict the plastic zone distribution and displacements of cavern periphery, which are nearly identical to those of the true field.

The impoundment of China’s Three Gorges Reservoir has led to the revival of many old landslides along the bank, and the annual fluctuation in water level of 30 m is likely to affect the creep deformation of these landslides. Through a field investigation of Huangniba landslide in the Three Gorges Reservoir Area, the local deformation signs and field monitoring data were analyzed. It was preliminarily considered that this landslide was currently at the creep stage and the creep rate was affected by the reservoir level variation. In order to carry out further research on the effect of reservoir level variation on the landslide movement, the finite element method was used to establish the seepage–stress coupling model of Huangniba landslide based on the seepage–stress coupling theory and taking into account the creep behavior of landslide material. The model was used to simulate the variation characteristics of the seepage field, stress field, and displacement field in the landslide during 6 years of cycles of reservoir level variation. Based on the numerical simulation results and field monitoring data, the deformation mechanism of the landslide was discussed. Finally, the sensitivity of the parameters in the creep model to the simulation results was discussed. The results show that creep deformation is the main deformation mechanism of Huangniba landslide, and it is obviously affected by the drawdown of the reservoir water level. During drawdown of the reservoir level, the pore water pressure inside the landslide decreases, resulting in an increase in effective creep stress and creep strain rate, thus accelerating creep deformation. The results of this study will provide a reference for the deformation mechanism of such creeping landslides subjecting to reservoir water level fluctuation.

The objectives of this paper are (1) to introduce a numerical first order method to calculate the gas containment reliability within a heterogeneous, two-dimensional, unlined rock caverns (URCs), and (2) to suggest a strategy for improving the gas containment reliability. In order to achieve these goals, we first analyzed the spatial variability of saturated hydraulic conductivity (Ks) at a field site. We then conducted deterministic simulations to demonstrate the importance of heterogeneity of Ks in the analysis of gas tightness performance of URCs. Considering the uncertainty of the heterogeneity in the real world situations, we subsequently developed a numerical first order method (NFOM) to determine the gas tightness reliability at crucial locations of URCs. Using the NFOM, the effect of spatial variability of Ks on gas tightness reliability was investigated. Results show that as variance or spatial structure anisotropy of Ks increases, most of the gas tightness reliability at crucial locations reduces. Meanwhile, we compare the results of NFOM with those of Monte Carlo simulation, and we find the accuracy of NFOM is mainly affected by the magnitude of the variance of Ks. At last, for improving gas containment reliability at crucial locations at this study site, we suggest that vertical water-curtain holes should be installed in the pillar rather than increasing density of horizontal water-curtain boreholes.

This paper develops a sequential displacement data collection and back analysis approach for mapping spatially distributed Young’s modulus (E) in a rock mass during the excavation of an unlined rock cavern (URC). Results show that this approach provides an unbiased estimate of the E field and its uncertainty. It also reveals a more detailed E distribution than kriging approach, which is based on samples of E values from boreholes before excavations. Further, predicted shear strain distribution and displacement of cavern periphery based on the estimates from this approach are more accurate than those based on the kriging estimate.

An adaptive sampling approach is proposed, which can sample spatially varying shear strength parameters efficiently to reduce uncertainty in the slope stability analysis. This approach employs a limit equilibrium model and stochastic conditional methodology to determine the likely sampling locations. Karhunen-Loeve expansion is used to conduct the conditional Monte Carlo simulation. A first-order analysis is also proposed to ease the computational burden associated with Monte Carlo simulation. These approaches are then tested using borehole data from a field site. Results indicate that the proposed adaptive sampling approach is an effective and efficient sampling scheme for reducing uncertainty in slope stability analysis.

A cross-correlation analysis is conducted to determine the impacts of the heterogeneity of hydraulic conductivity K s , soil cohesion c ′ and soil friction angle (tan φ ′) on the uncertainty of slope stability in time and space during rainfall. We find the relative importance of tan φ ′ and c ′ depends on the effective stress. While the sensitivity of the stability to the variability of K s is small, the large coefficient of variation of K s may exacerbate the variability of pore-water pressure. Therefore, characterizing the heterogeneity of hydraulic properties and pore-water distribution in the field is critical to the stability analysis.

This study proposes a cross-correlation map-based borehole deployment approach for two-dimensional probabilistic slope stability analysis. This approach designs the layout of the proper number of boreholes based on the cross-correlation between the factor of safety and spatially variable soil strength every part of a slope. Numerically synthesized, undrained slopes are investigated as examples to illustrate the effectiveness of the proposed approach. Results demonstrate that the proposed approach is viable, and the cross-correlation maps are the appropriate metric for design slope borehole deployment. Using the cross-correlation maps, a small number of boreholes can sufficiently capture the large-scale heterogeneities that are critical to the slope stability. This information can help to identify the slip surface and improve the slope stability analysis. The small-scale heterogeneity, due to its short correlation structure or the residual covariance of the soil property field after conditioning using the borehole data, leads to a small amount of uncertainty in slope stability analysis. This small uncertainty could be vital to the slope stability analysis when the slope stability is close to the limit equilibrium state.

Cost-effective sampling strategies to understand hydrologic processes in a hillslope are essential to the estimation of hillslope seepage and to the evaluation of slope stability. The objectives of this paper are (a) to introduce a stochastic cross-correlation analysis to hillslope hydrologic processes and stability investigation and (b) to develop a cost-effective sampling strategy to reduce the pore-water pressure uncertainty at the region of our interest. The concept of stochastic representation of spatial variabilities of soil hydraulic properties is introduced first. We then develop a first-order analysis method to determine spatiotemporal distribution of pore-water pressure head (P) variance (unconditional variance or uncertainty) due to spatial variability of saturated hydraulic conductivity (Ks) in a variably saturated hillslope during rainfall. Subsequently, a cross-correlation analysis is presented, which quantifies the spatial correlation between P at a given location and Ks at any part of a hillslope under a transient infiltration event. We afterward formulate a first-order approximation of residual P variance (conditional variance or uncertainty) due to inclusions of Ks measurements. The developed methodology is applied to synthetic, heterogeneous, two-dimensional hillslopes to investigate the effectiveness of several Ks sampling schemes. Results of this investigation show that boreholes and sampling locations should be placed at an interval of one correlation scale. They should be distributed over an area covering several correlation scales, rather than clustered together at the largest cross-correlation region or at regions where prediction uncertainty is large (where our interest and concern are). Further, the results demonstrate that increasing the sampling density is useful but inefficient. Layering structures of hillslopes reduce the number of boreholes and samples required. At last, a cost-effective sampling strategy for study of slope stability based on cross-correlation is suggested, which minimizes the prediction uncertainty of P at critical locations.

This paper develops an analytical approach for reliability analysis of infinite slope stability in presence of spatially variable shear strength parameters. The analytical approach considers spatial autocorrelation of each parameter and cross-correlations between different parameters. It is robust, computational efficient and provides insight to the importance of spatial correlation scale on slope reliability analysis. This paper also explores the difference in continuous and discrete random fields and emphasizes the importance of fine discretization in relation to correlation scale. Finally, it shows that conditioning the stability analysis with information about trends and spatial data leads to reliability assessments with less uncertainty.

This study first discusses the conditional mean, realizations, and effective hydraulic conductivity in a theoretical framework. It then introduces Monte Carlo simulation (MCS) algorithms for constraining the outcome by either hydraulic conductivity (K) samples or hydraulic head (h) measurements from the hydraulic tomographic survey (HT). It demonstrates that kriging using K measurements leads to a conditional mean K field, while inverse modeling using successive linear estimator (SLE) with head measurements of HT yields the conditional effective K field. The effects of conditioning using K measurements are different from those using heads. Besides, the conditional effective K leads to the unbiased prediction of the head that honors the observed head at measurement locations. More importantly, the study reveals that the harmonic and geometric means of conditional realizations of K fields of MCS, given head measurements, are equivalent to the conditional effective K in one- and two-dimensional flows, respectively. The first-order approximation in the SLE results in a conditional covariance similar to that from MCS with smaller magnitudes. Despite the difference, all approaches predict unbiased conditional mean head behaviors.

A displacement back analysis algorithm is developed, considering the time-dependent effect of the rock mass. It can map spatially distributed the first elastic modulus ( E 1 ), viscidity coefficient ( η 1 ), and the second elastic modulus ( E 2 ) of the Kelvin-Voigt viscoelastic constitutive model (VCM) and the Poynting-Thomson VCM in a rock mass by fusion of the observed displacement data from the excavation of an unlined rock cavern. The algorithm is tested and validated using numerical experiments with a synthetic heterogeneous rock mass. The results of the experiments show that this approach yields unbiased estimates of E 1 , η 1 , and E 2 fields and quantifies their uncertainty. Further, the estimated fields closely predict shear strain distribution and displacements field in the example.

Rock discontinuities significantly influence the deformation as well as strength of rock masses. Identification of rock discontinuity sets is one of the fundamental issue in rock mechanics. In this study, a new clustering method is developed to automatically identify rock discontinuity sets. The method is established on account of differential evolution, which is a robust and global optimization algorithm. An improved encoding approach was used to realize the full automation of algorithm. The main parameters of the algorithm are determined by self-adaptation techniques. The performance of the new algorithm was studied using an artificial data set. The clustering results demonstrate that the new algorithm could well identify discontinuity sets. Furthermore, the new algorithm is applied to analyzing discontinuity data collected at an underground cavern site, and satisfactory result is obtained. Additional advantage is that the method is totally automatic, without selecting proper initial cluster centers and specifying the number of discontinuity sets.

Knowledge of the fracture hydraulic aperture and its relation to the mechanical aperture and normal stress is urgently needed in engineering construction and analytical research at the engineering field scale. A new method based on the in situ borehole camera measurement and borehole water-pressure test is proposed for the calculation of the fracture hydraulic aperture. This method comprises six steps. The first step is to obtain the equivalent hydraulic conductivity of the test section from borehole water-pressure tests. The second step is a tentative calculation to obtain the qualitative relation between the reduction coefficient and the mechanical aperture obtained from borehole camera measurements. The third step is to choose the preliminary reduction coefficient for obtaining the initial hydraulic aperture. The remaining three steps are to optimize, using the genetic algorithm, the hydraulic apertures of fractures with high uncertainty. The method is then applied to a fractured granite engineering area whose purpose is the construction of an underground water-sealed storage cavern for liquefied petroleum gas. The probability distribution characteristics of the hydraulic aperture, the relationship between the hydraulic aperture and the mechanical aperture, the hydraulic aperture and the normal stress, and the differences between altered fractures and fresh fractures are all analyzed. Based on the effects of the engineering applications, the method is proved to be feasible and reliable. More importantly, the results of the hydraulic aperture obtained in this paper are different from those results elicited from laboratory tests, and the reasons are discussed in the paper.

It rains rarely in the northwest of arid and semi-arid regions. The roadbed is not saturated and the internal moisture changes dynamically. The moisture content of the roadbed has a great influence on the roadbed strength significantly. The roadbed moisture status is the key factor to design and evaluate the bearing capacity of the subgrade bed. Model test in the research was used in the research. The self-developed subgrade bed dynamic moisture model test is introduced. The precipitation intensity, the rain interval, the subgrade bed compaction and other factors on the impact of moisture were considered. Studies have shown that embankment slope measuring point reaches saturation after the precipitation firstly. The roadbed internal parts and the downwards parts are followed then. The water content of each measuring point rises firstly and then shows a stable trend. The subgrade bed moisture lags seriously. It does not change for a long time after raining. And with the changing, it would not restore to normal level in a long time. The slope permeability coefficient and permeability coefficient of silty clay was got, which is useful for engineering applications and numerical experiments.

This study focuses on mercury slag in the Tongren area of Guizhou Province, China. Computed tomography (CT) is used with uniaxial and triaxial compression tests to examine the mechanical changes in cemented mercury slag and its formation. The CT results for the uniaxial compression test reveal the overall failure process of the mercury slag structure. Based on the coarse-grained soil triaxial test, a modified Duncan-Chang model is compared with the actual monitoring results and is found to be suitable for the analysis of the slag constitutive model.

The mechanical parameters of the rock masses are scale dependent because of the existence of the discontinuities. The self-similarity of the discontinuities makes the application of fractal theory in the description of the rock mass structure possible. The novel point in this study is that the structure representative elementary volume (SREV) of rock mass is proposed. Rock mass structures were obtained through the two-dimensional discontinuity network simulation results, from which ten pieces of square rock mass specimens were chosen. The side lengths of the specimens were increased in turn from 1m to 10m. And the fractal dimension of each specimen with different sizes was calculated by the box-counting principal of the fractal geometry. The fractal dimensions of the rack mass structures became larger with their side lengths increasing, and finally stable. And the SREV of the rock mass was determined based on the variation rule of the fractal dimensions. Further, the relation between the structure representative elementary volume (SREV) and mechanical parameter representative elementary volume (REV) was qualitatively analyzed from the strength differences between the discontinuities and intact rock. And the conclusion was inferred that the size of the SREV was the upper limit of mechanical parameter REV. Meanwhile, the conclusion was verified by the results of the finite element method. This study can provided a referring value for the estimation of the mechanical parameter REV in future.

Zhangjiaba-Enshi 500kV Transmission Line is a backbone network in the West to East Power Transmission Project of China, which passes through the factory area of Chongqing Sanxing Iron Mine Factory. According to solving the additional stress on foundation rock produced by tower load based on the Boussinesq theory and the redistribution of surrounding rock stress resulting from iron mining computed by using the calculation formula for redistribution stress on circular chamber in rock mass, this paper analyzes and demonstrates the impact of Zhangjiaba-Enshi Line N327 tower footing pressure mine on mining within the range of mining scheme, and determines that there is no mutual impact between the Zhangjiaba-Enshi Line N327 tower and exploitation of Sanxing ore horizon.

On the base of the obtained materials and considering the factors of composition features, dynamic mechanism and deformation-motion characteristics, the three-dimension numerical simulation model is generated. And the parameters of Young module, passion ratio and shear strength are obtained. Then the calculation conditions are extracted from the combination of the inducible factors and the displacement features. After that, the deformation failure are simulated by the FLAC3D code, and the results are compared to the monitoring data. The results indicate that the influence of the water impoundment on the stability of the landslide is small, the water descending is large. For the front part monitoring points, the amounts and the curve shapes of the numerical calculation results are accord with the practical ones, but for the monitoring point in back there are only the similarities in the curve shapes, and the amounts are a little smaller.

According to the analysis of the landslide monitoring data, it is revealed that the amount of the cumulative displacement of the landslide depends on the monitoring cycle. And the trajectory curve of monitoring point has the fractal characteristics. The fractal dimension of the landslide internal points’ movement direction is various with the landslide development, which is decreased from the generation to the deformation and then to the damage. Meanwhile, based on the fractal boxing counting theorem, the program in Matlab is created to calculate the box dimension of the curve. Take a reviving landslide in Three-Gorge as an example, the fractal dimensions of the surface GPS monitoring points’ trajectory curves from 2007 to 2009 are obtained, and the dimension of each point is close to 1. The result indicates that this landslide is in the plastic deformation stage. It is the same with the landslide actual deformation. Therefore, the fractal theory has a great significance in the effective use of the monitoring data, the reorganization of the evolving stage and the prediction of the deformation trend for the landslide.

Taking a landslide in the three gorges reservoir area as an example and considering the seepage field in different time periods with rise and fall of reservoir water level of the eight conditions, we use GEO-STUDIO / SEEP module to establish a seepage model and to calculate the distribution of seepage. The results showed that: the groundwater saturation line appears in the back-phenomenon during a certain range of slope in the rising water level, saturation line was concave shape, and with the rate of increase in water level increased and that concavity gradually increase; the groundwater saturation line appears in the downstream phenomenon during a certain range of slope in the drawdown water level, saturation line was convex shape, and with the rate of decline in water level increased and that convexity increases. The effective simulation studies of the greatly and cyclical fluctuations of water level under the slope seepage field has a certain reference meaning to the landslide control in the reservoir water level fluctuations about reservoir bank landslide.

The Grey Model GM (1, 1) is extensively used in deformation prediction of deep excavation, which is very important for design and construction of foundation excavation. The Grey Model GM (1, 1) is based on the equal interval data. So it is difficult to predict when the data is unequal. For the shortcoming, the Grey Model GM (1, 1) is improved. The difference which is formed when unequal interval is transformed to interval is adjusted by unit time coefficient. So the unequal interval Grey Model GM (1, 1) is obtained after reversing the equal interval sequence. The deformation prediction is made by a deep excavation in Wuhan, Hubei, China. Through comparison and analysis on the prediction and actual data, it shows that unequal interval Grey Model GM (1, 1) is more closed to the reality.

During the construction of cities in mountain area, plenty of human waste-dump is produced because of the topographic conditions. In order to solve the problem of site leveling and rock spoils placing, the dumping site construction become an unavoidably problem which concerns two main problems-the stability of rock filling and the drain of ravine. This paper selects the dumping site of the Huang Jia ravine (to be built) as a case, which is a rock filling in Badong county that is an emigratory city of the reservoir region. The source of materials in the spoil site comes from the waste of landslide prevention program. Considering the engineering geological condition, hydrological geological and the characteristics of the rock filling slope, the possible damage mode of the rock filling after filling is speculated. On that basis, the un-equilibrium pushing method is used to calculate the stability of rock filling slope . Consulting the principles of rockfill dam in hydropower engineering ,the comprehensive protection measures are adopted to ensure the stability of the rock filling which includes canal revetment rolling and supporting structure . So, the protection design for the rock filling is a new method and approach of urban planning and environmental protection for the emigratory towns in reservoir region. It also has an important social and economic benefit.