Search

The Monte Carlo simulation (MCS) is generally accepted as an accurate approximation method in slope reliability analysis. However, low efficiency hinders its use. Based on the online sequential extreme learning machine (OS-ELM), the OS-ELM-MCS method is proposed, which overcomes the requirement of calculating the safety factor, respectively, when using a conventional MCS for reliability analysis. Combined with the multi-initial points sequential quadratic programming (MSQP) algorithm, a search method for probabilistic critical slip surfaces with arbitrary shapes is introduced. It is possible to conduct both a reliability analysis and deterministic analysis under the same algorithm framework. Based on the proposed method, reliability and deterministic analyses of two cases are carried out. Compared with the results of other methods, the accuracy of the reliability and deterministic analysis method is verified. This verifies that the accuracy and time performance of the proposed method are better than those of conventional algorithms. The results of these case studies reveal the differences between the conclusions of the reliability and deterministic analyses. Therefore, it is necessary to combine reliability analysis and deterministic analysis to improve the credibility of stability analysis results.

The motivation behind this work was to make a first attempt at gaining molecular-level insights into the structural and dynamical properties of H2O molecules confined within albite-quartz system under cyclic thermal loading, where CLAYFF force field was introduced into Forcite module. Derived from the distance variations of the tetrahedral atoms surrounding the Na position and RDF, the movement tendency of Na atom to be near Al atom and a stronger interaction between albite and H2O molecules can be observed. Accepting H-bonds from the H2O molecules near-surface are important for the development of continuous H-bond networks across the interfacial region. The discrepancy of the orientation order of H2O molecules and the H-bond configurations resulted from long-term thermal cycling are largely responsible for the structure and dynamics of near-surface H2O molecules.

The existing empirical methods of the seepage coefficient for clay have difficulty in parameter acquisition and are poor in calculation accuracy, and it is possible to find reasonable ones based on the mature empirical methods of coarse-grained soil. Firstly, the permeation mechanism of clay was analysed including influencing factors, spatial process, and parameter calculation, and the ineffective and effective voids were defined; then the empirical methods of clay and coarse-grained soil were summarised and listed. Secondly, clay was put equivalent to coarse-grained soil according to bound-water consolidation, and the parameter “equivalent void ratio” was introduced to establish the equivalent calculation methods. Finally, the liquid-plastic limit method determining the volume of ineffective voids was explained, and the feasibility of equivalent calculation methods was evaluated by three examples. The results show that seepage, permeation, and effective permeation are three different concepts; groundwater permeates in clay via the effective void. For certain soil, the increasing sequence of permeability coefficients is the seepage coefficient, permeation coefficient, and effective permeation coefficient. Introduction of the “equivalent void ratio” unifies the calculation of the seepage coefficient for clay and coarse-grained soil. The maximum of the bound-water content is about 0.9 time the size of liquid limit. The Mesri equation and the equivalent calculation method of Terzaghi or Curson–Karman are suitable for calculating the seepage coefficient of clay for the closest results to experimental values.

In this work, we make a first attempt at performing a molecular dynamic simulation to gain insights into the transport characteristics of H2O molecules confined in sandwiched albite-quartz system, where a mechanical loading couples a thermal cycling was carried out·H2O molecules were placed within the vacuum gap of the albite-quartz slab to accomplish the sandwich model. Based on the viewpoint of energetics aspect, the coulombic interactions are the dominant contributors to the total potential energy. The diffusion coefficient, orientation parameter and hydrogen bonding were examined for analysis of the transport characteristics of confined H2O molecules. Not only the water–mineral interaction but also the substrate structure reflects the dynamics of confined H2O molecules, as evident by qualitatively analyzing the trajectories of some selected H2O molecules located in different regions. The cyclic thermal–mechanical (T-M) coupling contribute a wide band distribution after 1000th cycles instead of two distinct peaks after the 100th cycles. The decrease in amplitude occurring primarily around 1.7 A is indicative of a weaken H-Bond and a greater rotational freedom of those molecules, leading to the gathering of H2O molecules near quartz and albite slabs and a dense arrangement of the H2O molecules in the inter-spacing region, which could be ascribed to the interconnected aspect of diffusion process.

Proper selection of similar materials is the key to the simulation of engineering prototypes. According to the similarity theory of geomechanical model tests, a novel similar material was developed after a great number of mixture ratio tests. The similar material consisted of barite powder and sand as the coarse aggregates, epoxy resin, polyamide, silicone rubber and a silicone rubber curing agent as the adhesive, and gasoline as the solvent. The mechanical tests on this similar material indicated that the material properties were stable and the manufacturing process was simple. Hence, the similar material can meet the requirements of large-scale model tests. The similar material was applied in the model test on a deep-buried tunnel under high in-situ stresses. The deformation and failure process of the tunnel were successfully simulated, and the failure pattern of the tunnel was obtained, which can provide an efficient basis for tunnel design and construction.

Ground Penetrating Radar (GPR) is a feasible remote sensing tool for surveying subsurface geo-structure. These structure characteristics are recorded in radar signal profiles by means of echo signal detection, amplitude and phase estimation. Besides the energy attenuation and absorption of GPR electromagnetic (EM) pulse during its propagating into subsurface from a transmitting antenna, the strong interferences such as multiples, background scatters, clutters and random noise often make the weak signal of structure signatures hardly distinguishable from them. This paper focuses on detecting rock fractures with multiple signal classification (MUSIC) under complex environment. By surveying data at experimental site it is shown that this method can efficiently achieve sparse representation of subsurface structures and yields discriminative fracture signature for geological interpretation.

Current literature on the heavy metal pollution of soil geotechnical properties of the still small, mostly in construction as a general soil treated, leads to irrational contaminated soil foundation, building foundations, rock slope deal with other issues. After the elements of rock and soil contaminated with heavy metals, colloidal particles are dissolution, bond strength is destroyed and changed the internal structure of the soil, resulting in rock and soil void ratio, compression increases, reducing the shear strength, bearing capacity decline changes in nature. Currently on the engineering properties of rock and soil heavy metal pollution, curing mechanism, the research achievements on prevention measures, mostly in the construction as a general soil treatment or no treatment, causing pollution rock embankment, slope, building foundations and other Jean split, collapse engineering accidents. So the study of rock and soil pollution prevention measures for the evaluation and treatment of heavy metal pollution rock land (road) group, slope, and the rational use of heavy metal pollution of soil resources is important.

Based on the prototype of a mine, a physical simulation test is conducted. The characteristics of the deformation and failure of the ground surface and the wall rock around a goaf, as well as the creep behavior of the wall rock deformation and the failure mechanism, are analyzed. The simulation test has greatly improved our understanding on the wall rock's deformation and failure characteristics. For the first time, digital close-range photogrammetry was used to measure the displacements in a sectional model test. The measurements by this technique agreed very well with those obtained by other methods, such as using dial gauges.

Biaxial compression model tests on rockmass containing intermittent joints under plane stress condition were carried out in this study, where the laser speckle photo technique was used for measuring the displacement field. The results obtained have indicated that the laser speckle method was effective and the measuring value was about 14% less than the measuring value of dial gauges. Based on the displacement field and the principal stress field which were measured by laser speckle photo technique, dial gauges and strain gauges, the angle of wing incipient crack, the evolution of stress field at the joint tip and the path of crack extension were deeply studied. The deformation and failure characteristics, including the fracture mechanism of rockmass, were also analyzed in this study.

Based on the results of model tests, the deformation and facture mechanisms of brittle rockmass containing coplanar close intermittent joints under direct shear condition were analysed , then the incipient crack strength and communicating destruction criterion of such rockmass were proposed in this paper. It was shown that the computing results suited the real measuring values well by comparing them, which indicated the criterions was reasonable ,reliable and has both the theory and construction significances.

Highway slope is an important part in the design and construction of highway. Especially in the complex geological condition area, road slope disasters occur frequently. So the stability of road slope is very essential to the safe traffic and the safety of human lives and their properties along the road. After the analysis of the existing methods of deformation measurement to physical model of highway slope, this paper introduces the theory and application of digital close range photogrammetry in deformation measurement of highway slope models. An ordinary digital SLR camera is employed and multi-intersection photography is used to take images of slope model in the project. The photogrammetric bundle adjustment is applied to compute 3D coordinates of artificial deformation monitoring target points on the surface of slope model. Then the cumulative displacement of each deformation monitoring target point is calculated based on their object coordinates in order to provide underlying data for the design of road slope and analysis of rock and soil mechanics.