Explore the vast range of titles available.

Based on the concept of the representative elementary volume (REV) and the synthetic rock mass (SRM) modeling technique, a DFN–DEM multi-scale modeling approach is proposed for modeling excavation responses in jointed rock masses. Discrete fracture networks (DFNs) are generated using MoFrac. For a given volume of jointed rock masses, multi-scale DFN models are constructed according to the hierarchical order of fracture size. Based on the DFN models of various scales, equivalent rock mass properties are obtained using 3DEC SRM models. A tunnel excavation simulation using data from the Äspö TAS08 tunnel is conducted to demonstrate the applicability of the proposed multi-scale modeling approach. The modeling results show that it is efficient to model the mechanical response of the rock mass using the proposed approach. The proposed approach has the advantages of both equivalent continuum and discontinuum methods, with a higher degree of accuracy compared with the pure continuum approach and a less computational effort compared with the pure discontinuum approach.

Naturally fractured rock mass is highly inhomogeneous and contains geological discontinuities at various length scales. Hydraulic fracture stimulation in such a medium could result in complex fracture systems instead of simple planar fractures. In this study, we carried out fully coupled multiscale numerical analysis to investigate some key coupled processes of fluid-driven fracture propagation in naturally fractured rock mass. The numerical analysis follows the concept of the synthetic rock mass (SRM) method initially developed in the discrete element method (DEM). We introduce a total of five case study examples, including fracture initiation and near wellbore tortuosity, hydraulic fracture interaction with natural fractures, multi-stage hydraulic fracturing with discrete fracture network (DFN), in-fill well fracturing and frac hits after depletion-induced stress change, and induced seismicity associated with fault reactivation. Through those case studies, we demonstrate that with an advanced numerical modeling tool, the complex fracturing associated with hydraulic fracturing in naturally fractured rock mass can be qualitatively analyzed and the extent of various uncertainties can be assessed.

As one of the most common failure forms of discontinuity-controlled rock slopes, wedge failure is likely to occur in a wide range of geologic and geometric conditions. In this study, the wedge failure of rock slopes and the movement and disaster processes after failure are investigated using 3D discontinuous deformation analysis (DDA). Compared with the analytical solutions derived from a typical rock wedge model, the performance of the original 3D DDA for analyzing the wedge stability under different geometrical and physical parameters is presented. The deficiency of the joint contact model in 3D DDA under critical state is improved. The improved 3D DDA is used to simulate a rock slope subjected to wedge failure in Tibet Autonomous Region, and the failure of the dangerous rock masses and movement of the formed blocks under different discontinuity cutting are discussed. The improved 3D DDA has high accuracy in calculating wedge critical stability and sliding after failure. The actual wedge slope presents sliding failure along the intersection line of structural planes, and tensile and shear failure and downward dislocations can be observed among blocks. The lateral deviation and deflection of wedge blocks occur constantly, showing 3D kinematic characteristics. With the increase of secondary discontinuities, the influence range of sub-blocks due to wedge failure becomes larger, constituting the geological disaster of the G318 national road. 3D DDA can evaluate wedge stability and analyze kinematic characteristics of wedge blocks, which lay a foundation for formulating disaster prevention countermeasures and reducing human casualties.

High and steep dangerous rock masses (DRMs) along reservoir banks pose significant threats to navigation and the adjacent towns. Taking the Longmen DRM (LDRM) in the Three Gorges reservoir area as an example, this paper analyzed the geological background and focused on the No.5 DRM of LDRM (LDRM-5) to investigate deformation characteristics and potential failure mechanisms. Furthermore, the rockslide tsunami risk of LDRM-5 was assessed. LDRM-5 is a typical pillar-shaped DRM with a distinct binary structure prone to sliding. Its boundaries are well-defined. The lower part of LDRM-5, situated within the reservoir fluctuation zone, comprises fragmented thin-layered argillaceous limestone with Karst breccia interlayer, and was considered to control the stability of the steep slope directly. In the future, the base rock of LDRM-5 might collapse due to long-term erosion from fluctuating reservoir water and constant pressure from the slope above, potentially resulting in overall slope failure. A granular flow model was employed to assess the tsunami risk posed by LDRM-5. Results show that the rockslide-generated tsunami exhibits greater propagation velocity at the water level of 175 m, while displaying a higher wave height at 145 m water level. At 145 m water level, the tsunami run-up on the opposite bank can reach 24.3 m, posing an extremely high-risk area covering 102.55 × 104 m2 and threatening a riverbank stretch of 16.03 km. At 175 m water level, the extremely high-risk area decreases to 45.31 × 104 m2, endangering a 7.85 km riverbank stretch. This study can provide a reference for research on failure mechanisms and tsunami risks of other high-steep DRMs in reservoir areas.

A rockfall is a typical dynamic problem of a discontinuous block system originating from a dangerous rock mass and always presents serious geo-hazards along highway slopes in mountainous areas. This study aims to investigate the failure mechanisms and movement characteristics of rockfalls through a three-dimensional discontinuous deformation analysis (3D DDA) method and attempts to comprehensively examine the complicated kinematic process of rockfall disasters. In terms of the initial failure and post-movement characteristics (i.e., motion trajectory and kinetic energy) of a rockfall, the effectiveness of 3D DDA is verified by comparing its results with those of laboratory experiments. Taking the K4580 typical high-steep slope undergoing rockfalls along the G318 national highway in Tibet as an example, the initiation and failure of a single boulder and a large-scale rock mass at the source area were simulated by 3D DDA. Then, the movement characteristics of the boulder and massive collapsing rocks along the slopes of different geometrical characteristics, i.e., the slopes before the landslide and after the shallow and deep landslides, were studied. The results show that the 3D DDA has significant advantages in analysing the failure mechanisms of slope rockfalls and can satisfactorily simulate the spatial movement (e.g., lateral deviation and deflection) of blocks by considering the 3D geometry of the slopes and blocks. The 3D DDA numerical simulation can predict the movement range, deposition position, and affected area of rockfall disasters, which can provide a basis for formulating disaster prevention countermeasures in actual projects.

Rock mass classification is essential for assessing the quality of macroscopic rock mass and is the basis for rock mass stability analysis and geotechnical engineering design. The joint observation technology limits traditional rock mass classification methods in that they only collect joint information from one-dimensional or two-dimensional space and cannot comprehensively obtain the joint occurrence in three-dimensional space. Consequently, empirical formulas are frequently used in studies on joint distribution laws, resulting in less accurate calculations of joint parameters. This study develops a method for classifying rock masses using a precise description of the joints. Initially, it utilizes the borehole camera and the Sirovision joint scanning system to acquire accurate three-dimensional joint occurrence data. The subjective and the objective weights of each evaluation index are derived from the analytic hierarchy process (AHP) and the CRITIC technique according to the cloud model theory. The game theory is then employed to determine the combined weight and evaluate the quality of a rock mass method with the cloud model (GA-CM). The proposed classification method is applied to the slope of an open-pit mine. The results indicate that compared to the traditional methods, the proposed method is objective, accurate, and field-applicable and also reduces the influence of subjective factors on rock mass quality evaluation and enhances the classification reliability.

A numerical characterization of a fractured rock mass and its mechanical behavior using a discontinuum approach was carried out utilizing lattice-spring-based synthetic rock mass (LS-SRM) models. First, LS-SRM models on a laboratory scale were created to reproduce standard rock mechanical tests on Triassic sandstone samples from a quarry in Germany. Subsequently, the intact rock properties were upscaled to an element volume representative for geotechnical applications, recalibrated and combined with a Discrete Fracture Network (DFN) model. The resulting fractured rock mass properties are compared to predictions from empirical relationships based on rock mass classification schemes and the DFN-Oda-Geomechanics approach. Modeling results reveal a significant reduction in the strength of the fractured rock mass compared to the intact rock, showing a high agreement with empirically calculated values. Results for the deformation modulus reveal a significant reduction induced by the fracture network and a good agreement compared to the results obtained by other approaches. It is shown that the LS-SRM allows analyzing the complex mechanical behavior during failure of rock masses, including crack initiation, propagation and coalescence. The resulting rock mass properties are key parameters for a wide range of geotechnical applications and can be used for large-scale numerical modeling as well.

A research study aimed at the extending the means of estimating ISRM (International Society for Rock Mechanics) geomechanical parameters through non-contact methodologies, in the frame of the remote survey of rock masses, is herein presented. It was conducted by coupling UAV-based photogrammetry and Infrared Thermography. Starting from georeferenced UAV surveys and the definition of rock masses’ RGB point clouds, different approaches for the extraction of discontinuity spatial data were herein compared according to the ISRM subjective and objective discontinuity sampling criteria. These were applied to a survey a window and along a scanline, both defined on the dense point clouds, to simulate a field rock mass survey, although carried out on remotely acquired data. Spatial discontinuity data were integrated via the analysis of dense point clouds built from IRT images, which represents a relatively new practice in remote sensing, and the processing of thermograms. Such procedures allowed the qualitative evaluation of the main geomechanical parameters of tested rock masses, such as aperture, persistence and weathering. Moreover, the novel parameters of Thermal-spacing (T-spacing) and Thermal-RQD (T-RQD) are herein introduced in a tentative attempt at extending the application field of IRT to remote rock mass surveys for practical purposes. The achieved results were validated by field campaign, demonstrating that a remote survey of rock masses can be conducted according to the ISRM procedures even on models built by integrating RGB and IRT photogrammetry. In fact, these two technologies are positively complementary and, besides being feasible, are characterized by a relatively quick and non-contact execution. Thanks to the positive and satisfactory results achieved herein, this research contributes to the implementation of the scientific and technical casuistry on the remote survey of rock masses, which is a technical field offering a wide range of applications.

A tunnelling project is normally initiated with a site investigation to determine the in situ rock mass conditions and to generate the basis for the tunnel design and rock support. However, since site investigations often are based on limited information (surface mapping, geophysical profiles, few bore holes, etc.), the estimation of the rock mass conditions may contain inaccuracies, resulting in underestimating the required rock support. The study hypothesised that these inaccuracies could be reduced using Measurement While Drilling (MWD) technology to assist in the decision-making process. A case study of two tunnels in the Stockholm bypass found the rock mass quality was severely overestimated by the site investigation; more than 45% of the investigated sections had a lower rock mass quality than expected. MWD data were recorded in 25 m grout holes and 6 m blast holes. The MWD data were normalised so that the long grout holes with larger hole diameters and the shorter blast holes with smaller hole diameters gave similar results. With normalised MWD data, it was possible to mimic the tunnel contour mapping; results showed good correlation with mapped Q-value and installed rock support. MWD technology can improve the accuracy of forecasting the rock mass ahead of the face. It can bridge the information gap between the early, somewhat uncertain geotechnical site investigation and the geological mapping done after excavation to optimise rock support.

Q -slope is an empirical rock slope engineering method for assessing the stability of excavated rock slopes in the field. Intended for use in reinforcement-free road or railway cuttings or in opencast mines, Q -slope allows geotechnical engineers to make potential adjustments to slope angles as rock mass conditions become apparent during construction. Through case studies across Asia, Australia, Central America, and Europe, a simple correlation between Q -slope and long-term stable slopes was established. Q -slope is designed such that it suggests stable, maintenance-free bench-face slope angles of, for instance, 40°–45°, 60°–65°, and 80°–85° with respective Q -slope values of approximately 0.1, 1.0, and 10. Q -slope was developed by supplementing the Q-system which has been extensively used for characterizing rock exposures, drill-core, and tunnels under construction for the last 40 years. The Q ′ parameters (RQD, J n , J a , and J r ) remain unchanged in Q -slope. However, a new method for applying J r / J a ratios to both sides of potential wedges is used, with relative orientation weightings for each side. The term J w , which is now termed J wice , takes into account long-term exposure to various climatic and environmental conditions such as intense erosive rainfall and ice-wedging effects. Slope-relevant SRF categories for slope surface conditions, stress-strength ratios, and major discontinuities such as faults, weakness zones, or joint swarms have also been incorporated. This paper discusses the applicability of the Q -slope method to slopes ranging from less than 5 m to more than 250 m in height in both civil and mining engineering projects.