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Elements of rock physics and their application to inversion and AVO studies
\"This book deals with a series of topics in rock physics, including elasticity, pore pressure, incompressibility of rocks and the Gassmann equation, fluid substitution, forward modeling and empirical equations, rock physics applications to AVO studies and inversion studies, and the Differential Effective Medium (DEM) method\"-- Provided by publisher.
Book
Analysis of Factors Influencing Tunnel Block Collapse in Blocky Rock Masses: Insights from Large-Scale Model Experiments and DDA Simulations
Block collapse is one of the most common geological disasters that occurs during the construction of tunnels in blocky rock masses and is characterized by sudden events and severe damage, which seriously threatens the safety of tunnel construction. To achieve effective control of block collapse, model experiments on tunnel block collapses with a scale of 200 × 125 × 23 cm were conducted to study the effect of the tunnel span on disasters in this paper. The height of block collapse increases with increasing tunnel span, which verifies the accuracy of the discontinuous deformation analysis method (DDA) in simulating block collapse by comparing the experimental results with the DDA simulation results. Then, the influencing factors of block collapse disasters were selected, and the effects of different influencing factors on tunnel block collapse were simulated based on the DDA method. According to the simulation results, the height and area of block collapse were obtained, and the influence laws of each factor on the height and area of block collapse were analyzed. Based on that, the impact levels of each factor on block collapses were divided. Finally, based on the K-means method, tunnel block collapses were divided into five levels according to the height and area of the block collapse, accounting for 28.6%, 32.5%, 23.4%, 11.7%, and 3.9%, respectively. To avoid block collapse, disposal measures were provided for different levels of tunnel block collapse in this paper, which can provide theoretical guidance for the safe construction of tunnels in blocky rock masses.HighlightsLarge-scale model experiments were conducted to study the effect of the tunnel span on block collapse.Factors influencing block collapse in tunnels were analyzed based on the DDA simulation results.Block collapses were divided into five levels according to the severity of the disaster based on the K-means method.Standards for prevention measures were established according to the different levels of tunnel block collapse.
Journal Article
When Large Deformation Analysis Meets Large Deformation Phenomenon: Comparative Study and Improvement
Large deformation phenomena in rock engineering are commonly key bottlenecks impeding engineering progress. Correspondingly, large deformation analysis in rock mechanics has a widespread impact on mechanism understanding, prevention, and control guidance. Various large deformation schemes broadly categorized as hypoelastic- and hyperelastic-based models exist in the literature and software. Without an understanding of the capabilities and demerits of these schemes, the diversity in choices inadvertently leads to pitfalls, placing engineering endeavors at a disadvantage. In this work, we review and compare the most prevalent schemes (including PK2-Green, Jaumann, Green–Naghdi, Truesdell, and hyperelastic-based schemes) from perspective of rock mechanics, with an emphasis on their application in rock engineering, and further develop a hyperelastic-based large deformation scheme (marked as Cauchy-Ln scheme) based on Cauchy stress and Hencky logarithm strain. The proposed model realizes the separation of material nonlinearity and geometry nonlinearity. Several typical large deformation phenomena in rock engineering are studied. The relationships between large deformation phenomena and large deformation analyses are clarified under different circumstances. Especially under large strain conditions, the PK2-Green scheme is enfeebled, and the hypoelastic-based scheme should be used with caution. For rock material with an apparent pressure-sensitive effect, the proposed Cauchy-Ln scheme is superior.HighlightsThe connections between large deformation phenomenon and large deformation analysis are delineated.Prevalent large deformation schemes are compared from a rock mechanics perspective with an emphasis on application in rock engineering.A newly hyperelastic-based large deformation numerical model, enhancing compatibility with rocks, is developed.
Journal Article
A Nodal-Based 3D Discontinuous Deformation Analysis Method with Contact Potential for Discrete Rock Block System
To analyze the movement of discrete rock block systems, a nodal-based three-dimensional discontinuous deformation analysis method with contact potential (3D-NDDACP) is proposed. In the proposed 3D-NDDACP method, tetrahedral FE meshes which can be effectively generated with existing mesh generator are adopted to discretize rock blocks to better capture their deformation. Additionally, the contact potential is incorporated to treat the contact between two adjacent blocks. The introduction of contact potential significantly simplifies the implementation of the proposed 3D-NDDACP method, since the contact force can be directly computed without distinguishing contact types between any two adjacent blocks. However, in the traditional 3D-DDA method it is essential to conduct contact type judgment before computing contact forces. Note that contact type judgment is not a trivial task for 3D problems, since many different contact types including point-to-point contact, point-to-edge contact, point-to-face contact and edge-to-edge contact are involved. With the proposed 3D-NDDACP method, three benchmark problems about the movement of rock block systems are investigated. Numerical results obtained with the proposed 3D-NDDACP method are in good agreement with the theoretical solution, which means that the proposed 3D-NDDACP method can reliably and correctly simulate the movement of rock block systems. The proposed 3D-NDDACP method warrants further investigation.HighlightsA nodal-based 3D DDA model is proposed for modeling the discrete rock block system.Contact forces are computed effectively using contact volumes, without the cumbersome contact type determination.Simplest and most versatile tetrahedral meshes are always available for the proposed model.
Journal Article
A possible mechanism of earthquake-induced landslides focusing on pulse-like ground motions
This paper proposes a mechanism of earthquake-induced landslides with pulse-like ground motion (PLGM) based on the discontinuous deformation analysis (DDA) method. In recent near-fault earthquake-induced landslides, the two phenomena confusing landslide researchers are observed. One is that large-scale landslides occurred in the area with small PGA but no landslide in the area with large PGA, for example, the landslides occurred during the 2016 Kumamoto earthquake. The other is that one side slopes collapsed while the opposite side slopes back to back remain stable. For example, most west-faced slopes collapsed while the east-faced slopes back to back remain stable in the 2018 Hokkaido earthquake. To explain the two phenomena in near-fault earthquake-induced landslides with PLGM, a symmetrical slope model subjected to different ground motions during these two earthquakes are analyzed and discussed by using the DDA method. The analysis results show that PLGM may be a major triggering factor for co-seismic landslides in the near-fault region, while PGA may not be the right parameter for the initiation of the earthquake-induced landslides. Meanwhile, the aspect of collapsed slope is related to both the velocity pulse of PLGM and strength parameters of the slope. The proposed mechanism for the earthquake-induced landslides in the near-fault region with PLGM considers both tensile and shear strengths of the slope, which can well explain the landslide initiation phenomena in the 2016 Kumamoto earthquake and the 2018 Hokkaido earthquake. The relationship between PLGM and forward directivity effect is also studied in combination with two earthquake cases to more accurately clarify the mechanism of the initiation of co-seismic landslides in the near-fault region.
Journal Article
Mechanism analysis and partition characteristics of a recent highway landslide in Southwest China based on a 3D multi-point deformation monitoring system
An increasing number of landslides are occurring during the construction of highways in mountainous areas all over the world. A recent highway landslide located in the mountainous region of Southwest China is taken as a representative example to carry out the initiation mechanism and deformation characteristics analysis, and study the intelligent partitioning method in this paper. The geological conditions of the landslide are obtained through detailed geological surveys and investigation. A three-dimensional (3D) monitoring network with a total of 72 multi-points, including 53 surface displacement monitoring points and 19 deep displacement monitoring holes, is established to examine the spatial deformation characteristics of the landslide for nearly 25 months. The monitoring results of the surface displacement show that the dynamic deformation of the landslide can be divided into three stages, namely initial deformation stage, accelerated deformation stage, and stabilization stage. Based on the strata distribution obtained by the borehole investigation and the results of deep displacement monitoring, the depth of the slip surface can be reliably determined. The smart contract method in blockchain technology combined with the multi-point monitoring dataset is novelty applied to realize the intelligent automatic partition of the highway landslide without any human involvement. This method can provide the basis for further independent analysis of different landslide zones. According to the investigation and analysis, the initiation mechanism for the highway landslides is attributed to both internal poor geological conditions and external intense precipitation and engineering excavation.
Journal Article
Experimental and Numerical Study on the Interface Behaviour Between the Rock Bolt and Bond Material
Conventional tunnelling methods (i.e., the drill and blast tunnelling method or the new Austrian tunnelling method) have been frequently applied for the construction of tunnels/caverns under a high overburden and with a large cross section. Under such adverse conditions, tunnel support materials may yield because of ground pressure and tunnel deformation. As a result, a tunnel may lose its stability due to a reduced effectiveness of the tunnel supports. Rock bolts have been widely used as an essential component of tunnel support, and many studies have been conducted on the performance of rock bolts in strengthening the jointed rock mass. However, there is a lack of understanding on the interface behaviour between the rock bolt and the bond material, especially the crack initiation and propagation inside the bond material. This study aims to investigate the interface behaviour between rock bolts and bond materials using laboratory tests (shear tests) and numerical simulations (Discontinuous deformation analysis). By assessing the impact of the key parameters in the rock bolting system, such as the ribs, rib angle, strength of the bond material and the confining pressure, we are able to better understand the supporting mechanism and the effects of rock bolting.
Journal Article
Implementation of Viscoelastic Artificial Boundary and Seismic Motion Input Method in Three-Dimensional Discontinuous Deformation Analysis Method
When applying the three-dimensional discontinuous deformation analysis (3D-DDA) method to simulate the dynamic response of rock mass in an earthquake, appropriate artificial boundaries and input methods should be considered. In this study, the 3D-DDA method was modified by introducing the viscoelastic artificial boundary and the seismic motion input method based on the wave field decomposition method and with the consideration of the lateral free-field wave. Subsequently, the correctness of the boundary and the input method was verified through numerical examples. The results of the numerical examples were almost consistent with the theoretical solution. The introduced viscoelastic artificial boundary and seismic motion input method improved the applicability of the 3D-DDA method and can be further applied to simulate actual engineering cases.HighlightsViscoelastic artificial boundary is applied and validated in 3D-DDA.The differences between viscoelastic boundary and existing boundaries are compared.Modified 3D-DDA can consider wave field decomposition and lateral free-field wave for seismic motion input.Feasibility of modified 3D-DDA to study the dynamic response of rock mass in an earthquake is studied.
Journal Article
Dynamic Coupled Hydromechanical Approach for Fractured Rock Mass Seepage Using Two-Dimensional Discontinuous Deformation Analysis
This paper introduces the development of a dynamic seepage network method (DSN) within a two-dimensional discontinuous deformation analysis (2D-DDA) framework. The primary goal is to identify actual fractures and seepage spaces, establish a seepage network, and automatically compute hydraulic water pressure within blocky systems. In addition, a new coupled dynamic hydromechanical model (DDA–DSN) is proposed to investigate seepage behavior in time-varying fractured rock masses. The DSN method tracks fracture propagation between blocks during seepage flow, while the DDA component characterizes the translation, rotation, and deformation of arbitrarily formed blocks. The paper covers fundamental theories, the determination of neighboring non-contact block pairs, the creation of seepage networks, hydraulic pressure calculations, and the integration of DDA and DSN in detail. Furthermore, the validity of the coupled DDA–DSN hydromechanical model is confirmed by comparing numerical results with experimental measurements. These results highlight the model’s effectiveness in capturing fluid flow behavior within fractured rock masses, emphasizing the exceptional capabilities of DSN in identifying seepage spaces, constructing seepage networks, and automatically computing hydraulic pressure. Overall, this proposed model holds significant promise for addressing engineering challenges related to seepage flow behavior inner the rock masses.HighlightsDeveloped a new algorithm for identifying the real fractures, forming the seepage pathways, and calculating the hydraulic water pressure on blocks automatically in 2D-DDA.Proposed a new coupled DDA–DSN model to investigate the seepage behavior in time-varying fractured rock mass systems.Checked validity of the DDA–DSN model by contrasting several numerical findings with experimental measurements.
Journal Article
Large Deformation Analysis and Stability Recheck of a Large Slope during the Construction Process of a Certain Hydropower Station
During the excavation process of a certain hydropower station project, cracks and significant deformations emerged on the slope. To guarantee the stability of the slope and the safety of construction, based on the actual construction circumstances and monitoring data on site, a three-dimensional model of the slope was established in this paper. The strength reduction method was employed to conduct a recheck and analysis on the stability of the slope of the power plant. The results indicate that under the designed support plan, the safety factor of the construction condition is 1.301. The slope deformation and the support stress level are in accordance with the monitoring data. There is no non-convergent deformation of the slope, fulfilling the design requirements of the specification. The current support plan is effective and feasible, and is capable of ensuring the safety and stability of the slope during the construction period.
Journal Article