Numerical Analysis of Railway Roadbed Stability with Respect to Underground Cavities and Rock Condition: A Case Study of Shafts at Majang Mine

Geotechnical approaches for the design of a railway tunnel section in andesite

The short and long-term stability of major excavations is crucial to the successful development and long-term performance of both the excavations and their mining function. Detailed geotechnical assessments and analyses are pivotal to understanding the causes of instability when planning a major excavation and are essential to performance forecasting and applying engineering and mitigation controls. This paper describes a mixed-method approach, which not only evaluates the suitability of a range of ground support regimes but provides a good practice framework that can be applied to future major excavation assessments during a feasibility study. This approach includes the collection of geological and geotechnical data, rock mass classification, the specification of strength and stress parameters, preliminary identification of support requirements using empirical methods, such as the Q, RMR, and GSI systems, kinematic joint and wedge analysis, and 2D and 3D numerical modelling. These methods take into consideration the local rock conditions and structural geology and the ground support response based on cover hole data to evaluate best the suitability of an underground excavation and related support elements before construction begins. The mixed-method approach was tested by assessing the construction of a new major excavation for an unnamed block cave operation. Detailed geotechnical data was obtained from two cover holes. The results identified the stress environment, the likely modes of failure, mean joint sets, potential wedge formations and key influences of joint properties, the likely failure zone, and the potential impact of the void created by caving. In addition, the approach allows a wide range of suitable support regimes to be assessed. The result was a support evaluation unique to the operation and local conditions. This framework helps to successfully determine the rock conditions and the effectiveness of various support designs in two and three dimensions where this type of analysis is essential to safely work in underground conditions that are adequately supported, which can be determined quickly and effectively using the mixed-method approach for evaluating ground support and rock mass conditions. Further steps are suggested to improve the approach’s usefulness subject to more data and analytic capabilities, including downhole geophysics, numerical modelling with a discrete fracture network, and synthetic rock mass modelling.

Several attempts have been made to assess the ultimate capacity, and sometimes the overall response, of cemented mine fill barricades. Many of these have incorporated elastic-plastic constitutive models which are known to be inferior when modelling non-linear plain or reinforced concrete behaviour. Furthermore, virtually all such studies have not systematically considered the surrounding host rock’s stiffness. This paper considers barricades with boundaries of both infinite and finite stiffness using advanced numerical analysis tools developed at the University of Toronto which have been specialised for reinforced concrete design in a civil engineering context. These peer-reviewed tools are internationally considered to be state-of-the-art. The first case considers the problem of modelling reinforced concrete barricades with infinitely stiff boundary conditions. A set of relevant, carefully controlled laboratory studies is reviewed and the numerical analysis technique is shown to be appropriate. Modelling is then carried out for the case of a barricade at Cayeli Mine where the loading was believed to be essentially fluid, and therefore the modelled boundary condition easily represented. The pre-peak load-deformation relationships are correlated between field monitoring and numerical model results with excellent agreement. The second case considers the problem of barricade boundaries with finite stiffness. Equations based on Timoshenko and Boussinesq solutions were developed to represent equivalent end restraints for the modelled barricade. A wide range of stiffness encompassing virtually all possible rock conditions was considered. Practicing mining engineers can use standardised underground mapping and rock mass classification techniques to determine what an appropriate end stiffness value would be for their mining conditions. It will be shown that barricade capacity varies significantly with host rock stiffness, and that the commonly made design assumption of a fully rigid boundary can result in unconservative over-prediction of barricade strength.

Fracture growth leading to mechanical spalling around deposition boreholes of an underground nuclear waste repository

Numerical Analysis of Rock-Socketed Piles under Combined Vertical-Lateral Loading

Safe rapid drifting – Support selection

Coupled thermo-mechanical constitutive damage model for sandstone

Performance based support design for horseshoe-shaped rock caverns using 2D numerical analysis

In this paper according to the results of a great quantity of tests and numerical calculations, it is pointed out that the surrounding rock with thickness of 1/3 span has mechanical characteristics of a thick flexural member in underground rock cave subjected to transverse blast loading. However, it approaches the stress state of free field outside country rock and the equation of thick plate theory under the loading of free field pressure may be applied to the solution of this problem. Therefore, the underground structure-country rock dynamic interaction may be described by dynamic equations of flexural members of thin plate and thick plate, which express linear and country rock respectively. The interaction force between the liner and country rock is expressed as contacting pressure function q(x, l). By solving system of simultaneous equations, the analytical solution for the dynamic analysis of arch-straight liner including elastic half space interaction effect is given and the analytical expression of function q(x, t) is obtained. This analytic solution will contribute to the study of some substantive problems of underground structure-medium dynamic interaction theoretically.

<p>Underground laboratories provide a unique environment for various industries and are a suitable place for developing new technologies for mining, geophysical surveys, radiation detection, as well as many other studies and measurements. Unfortunately, any operation in underground excavations is associated with exposure to many hazards not necessarily encountered in surface laboratories. One of the most dangerous events observed in underground conditions is the dynamic manifestation of rock mass pressure in form of rockburst, roof falls and mining tremors. Therefore, proper evaluation of geomechanical risk is a key element ensuring the safety of work in underground conditions. Finite Element Method-based numerical analysis is one of the tools which allow conducting a detailed geomechanical hazard assessment already at the object design stage. The results of such calculations may be the basis for the implementation of preventive measures before running up the underground facility.</p><p>Within this paper, the three-dimensional FEM-based numerical analysis of large-scale underground laboratory located in deep Polish copper mine was presented. The calculations were made with GTS NX software, which allowed determining the changes in the safety factor in surrounding of the analyzed area. Finally, the possibility of underground laboratory establishment, with respect to predicted stress and strain conditions, were determined.</p>

The preservation condition of historical buildings is closely related to their ventilation environment. This study focuses on the rock temples in Wudang Mountain, specifically comparing the ventilation conditions of Yinxian Rock and Huayang Rock. The following conclusions are drawn: (1) The main wind direction at Yinxian Rock aligns with its orientation, which is an easterly wind, while Huayang Rock experiences a westerly wind, deviating from its southwestern entrance; (2) Huayang Rock has significantly lower wind speeds compared to Yinxian Rock, with minimal airflow; (3) The surrounding environment of Huayang Rock features steep terrain, dense tree cover, and the presence of railings and other structures that impede wind entry into the cave, whereas Yinxian Rock is surrounded by fewer trees and has a flat terrain; (4) In terms of cave morphology, Yinxian Rock is completely open on the east side, while Huayang Rock’s opening accounts for only half of its area and is not directly aligned with the rock temple. In summary, Huayang Rock’s ventilation environment is inferior to that of Yinxian Rock, leading to more severe pathologies. It is inferred that Huayang Rock’s preservation issues are closely related to its poor ventilation environment. Therefore, improving its ventilation conditions is crucial for preventive conservation. Using environmental simulation, this study compares the ventilation conditions of Huayang Rock under different wind directions and speeds, identifies the two most ideal scenarios, and proposes several feasible solutions.

This research aims at estimating the temperature of the aquifer that supplies Assammaqieh well at the depth of 550 m, on the basis of chemical analyses and geothermometric techniques which are one of the methods used for searching for the renewable geothermal energy and conserving the environment. In this study, about twenty-two geothermometric indicators have been used. For verifying the results, these results have been compared with data and estimates of temperature of fluids of deep typical wells in New Zealand, and it has been noticed that the theoretical and actual results approach the limits of 95% in many indicators. The study has been restricted to the relations of Cations because they are the most reliable, and the least affected by dissolution and evaporation. Most of the indicators that are based on the four chemical elements: Calcium (Ca), Potassium (K), Sodium (Na), Magnesium (Mg), have been adopted. The laboratory analysis data of Assammaqieh well confirmed that it was hot sulphurous water that acquired its chemical properties from complicated geochemical conditions, underground thermal conditions and volcanic rock nature. It also turned out that the underground heating process was basically due to thermal conductivity and rock adjacency, and that Assammaqieh well was supplied with water from adjacent groundwater tables whose source was the penetration of surface water. It also appeared that most of the equations used in the search for geothermal energy revealed the presence of an aquifer of hot and very hot water, and they were compatible with the high thermal gradient in volcanic rocks. It also tuned out that 86% of the used geothermometric equations estimated the aquifer temperature of Assammaqieh well as being hot and very hot with around 135.5 Celsius (±20). The study concluded with the hypothesis that Akkar possessed a huge geothermal energy, and benefiting from this energy might put an end to the chronic problem of electricity in Lebanon, and opened up many prospects and uses that could participate in a sustainable and comprehensive development of Akkar and Lebanon as a whole.

An excavation damaged zone (EDZ) caused mainly by blasting is an important parameter for making reliable evaluations of the overall tunnel stability. Around a blasted tunnel, various rock properties are changed in the EDZ, which is dependent on the original rock properties, blasting design, and tunnel geometry. In this paper, the development of an EDZ and its influence on the mechanical behavior around an underground excavation were investigated using an in situ test and computer simulations. The variation of the rock properties in the EDZ was predicted by considering the blast design and compared with actual measurements using the Goodman jack test. The extent of the EDZ could be calculated from the characteristics of ground vibrations measured from a test blast. The reduction of the rock properties in EDZ could be predicted accurately with an overlapping effect due to sequential blasting. Numerical analyses using FLAC were made of several cases to determine the possible influence of the EDZ generated from different blasting designs and rock conditions.

Deformation Patterns and Surface Settlement Trough in Stratified Jointed Rock in Tunnel Excavation

Sandstone is one of the most studied rocks. This is due to the fact that it is often found in various engineering fields. Thus, the study of sandstone failure mechanisms, and generally, rocks failure is of great importance for solving particular engineering problems. However, repeating of in-situ (real loading) conditions of rocks in the laboratory faces well-known difficulties, and experiments are rather costly. Numerical simulation, as well as laboratory experiments, does not fully overcome the aforementioned obstacles, but it sufficiently enhances the understanding of deformation and fracture processes. The finite-difference simulation-based approach is utilized in this work. Initiation and propagation of fracture in weak porous sandstone specimens subjected to multiaxial loading which is accompanied by acoustic emission are simulated in this work.