Springer Science and Business Media LLC

The depleting coal deposits day by day required the introduction of novel methods of mining like highwall mining. Highwall mining is a method of extraction of coal blocked in the highwall. The method involves considerable challenges in the area of roof control and most importantly the stability of the highwall itself. Highwall mining has gained considerable importance all over the world, owing to the fact that the coal otherwise would not be extracted forever. This paper aims to assess the influence of varying conditions which can affect the stability of the highwall during highwall mining. The effect of gallery length, width of pillar and number of galleries are systematically studied through field investigations where a highwall mining was adopted first time in India. Initially, assessment was carried out using a numerical modelling approach and then the stability of the highwall is classified using multilinear regression, logistic regression and naive Bayes classifier. This will provide a mechanism to predict the stability of the highwall in future cases of similar conditions. The classification is done using statistical adaptive learning methods and a comparison of the methods is done.

Within the context of the phase IV (1994–1996) research and development activities at the Grimsel Test Site (GTS), Nagra developed, in collaboration with the Agence Nationale pour la Gestion des Déchets Radioactifs (Andra), an investigation project for the sealing of boreholes drilled from underground. The project had the following goals: The new concept developed in this project was to use highly compacted bentonite pellets only. The two techniques tested were Both techniques were tested in situ at the GTS to estimate their performance under realistic field conditions. The swelling pressures were monitored for 4 months after seal emplacement until an almost constant value was attained. Finally the hydraulic and mechanical performance of the seal was tested. It was found that the conductivities measured across the seal were equivalent to the matrix properties of the surrounding rock (2–5 × 10−12 m/s). The hydraulic testing also showed no linear preferential flow.

Due to the role of geological structure, the underground rock contains a large number of holes. In order to study the influence of the hole on the mechanical characteristics of the rock failure, the numerical simulation analysis of the intact rock and the rock with three shapes holes(circle, square, triangle) are carried out by using PFC2D. The results show that the rock strength varies with the shape of the hole. Circular holes have the least impact on strength and triangles have the greatest impact. At the same time, different holes shapes have different failure morphology, the intact rock sample forms a penetrating fracture zone inclined by 60°. For the circular hole, forms a through-fracture zone along the upper left and lower right corners. The square hole sample forms an "X"-shaped fracture zone along the four corners. For the triangular holes sample, the damage occurs first at the two positions of the left and right foot of the hole, and then the fracture zone is formed along the upper right corner and the two feet of the sample. Finally, theoretical analysis of stress distribution characteristics around the rock with circular holes is carried out. The compressive stress concentration occurs on the left and right sides of the circular hole, the tensile stress concentration occurs at the top and bottom boundary of the hole. And the tensile crack occurs at the top and bottom of the hole, tensile and shear mixed cracks appear on the left and right sides of the hole from numerical simulation. The crack distribution of numerical simulation is consistent with the theoretical stress analysis results.

The paper presents flexural analysis of laterally loaded piles considering nonlinear p–y curves and the modulus of elasticity of soil estimated from pressuremeter test data treating the pile as a beam on elastic foundation with the load coming at the top. Solution of the problem using nonlinear p–y curves (as suggested by Menard (1975)) is found using an iterative technique as well as elastic continuum approach (following Poulos and Davis approach). Deflection and bending moments were predicted at some designated points and compared with measured valued as reported in literature. The predicted values of deflection of the pile are generally on the higher side for elastic continuum approach. The deflection values when predicted by using nonlinear p–py curves are either lower or higher than the observed values depending on the rheological coefficient. However, the comparison of the results is found to be reasonable and well within the range of experimental errors.

With the increase of mining depth and scale, mine dynamic disasters related to coal-rock instability, such as rock burst, are becoming more and more serious, so it is very urgent to predict them accurately. At present, the method of borehole pressure relief is relatively effective for the prediction and control of rock burst. In this paper, the numerical simulation software PFC was used to study the influence of different drilling depth and location on mechanical properties, acoustic emission characteristics and damage evolution characteristics of coal-rock mass. The results show that the greater the drilling depth and the closer the drilling location is to the upper coal seam, the better the effect of destabilizing the impact-prone coal seam is. With the increase of drilling depth, the maximum value of acoustic emission events in coal-rock mass decreases first, and then stabilizes; with the increase of drilling location (height), the maximum value of acoustic emission events in coal-rock mass increases first, and then decreases; the stability of coal-rock can be monitored by the evolution law of acoustic emission. The failure modes of coal-rock samples with different drilling depths and locations are different, and large cracks mostly exist in the local part of coal-rock samples. The damage evolution of coal-rock mass can be divided into three stages: initial non-damage stage, slow increase stage and rapid increase stage. Different drilling depth and location have different effects on rock damage evolution characteristics.

Taking Chongqing Rail Transit Line 9 as the engineering background, this paper used ground penetrating radar to forecast the surrounding rock characteristics in front of the tunnel. It is considered that the geological conditions within 0–30 m in front of the tunnel face are complex, the structure is loose, the groundwater is developed, and the self stability of rock and soil is poor, which seriously affects the construction progress and the safety of life and property. Based on this, the reasonable construction and reinforcement measures are put forward, and the electromagnetic response analysis of the full space 3D forward modeling is carried out by using ANSYS software. It is considered that: the 3D forward modeling results of no unfavorable geological bodies show that the "water wave effect" of eddy current and electromagnetic induction intensity occurs in the whole space, which indicates that the results of numerical solution and analytical solution are similar, which provides the basis for further exploration of electromagnetic response characteristics of transient electromagnetic method. The 3D forward modeling results of typical water bearing unfavorable geological body show that the maximum eddy current is formed in the poor geological body, and the transient electromagnetic method is more sensitive to the low resistivity body. The results of 3D forward modeling of water filling of unfavorable geological bodies show that the greater the water filling, the stronger the electromagnetic response, while the abnormal characteristic response of semi water filled karst cave is relatively weak.

The study of contaminants propagation in fractured and karstic aquifers shows uncertainties caused by the conditions of anisotropy of the medium and by the presence of cavities and residual products that could make fluid flow and solute transport unforeseeable. Therefore, in aquifers characterized by fissured and fractured solid matrix, in order to set up remediation strategies, it is necessary to represent the conditions of groundwater flow and contaminant propagation in such a way as to take into consideration the high heterogeneity connected to the presence of fractures and channels that act as preferential flow ways. The study carried out in a specified site, located in the city of Bari, heavily contaminated by petroliferous substances allows to build a model able to simulate subterranean draining conditions that prove to be as near as possible to the real ones. This simulation could be helpful for the prevision of the dynamic behavior of the aquifer during the period of the treatment in order to allow optimizations on the technical and economical point of view and in order to check the effective functionality of the system in the presence of anthropic constraints.