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\"This book is intended as a reference book for advanced graduate students and research engineers in block-in-matrix rocks (bimrocks) or soil and rock mixtures (SRMs) or rock and soil aggregate (RSA). Bimrocks are complex formations characterized by competent rock inclusions floating in a weaker matrix. Typical types of bimrocks include a series of mixed geological or engineering masses such as mélanges, fault rocks, coarse pyroclastic rocks, breccias, sheared serpentines and waste dump mixture. Bimrock is especially different from the general soil and rock material, and the detection of the damage and fracture is still wide open to innovative research. Globally, there is widespread interest in investigating the geomechanical behaviors of bimrocks, such as deformation and strength characteristics, damage and fracture evolution and stability prediction of bimrock construction. However, the meso-structure factors control the whole mechanical properties of bimrocks, the source of the macroscopic deformation phenomenon is the meso-structural changes. Therefore, evaluation of the mesoscopic physical and mechanical properties, together with advanced testing technique, are attractive research topics in rock mechanics. As a result, comprehensive macroscopic and mesoscopic experimental investigations should be conducted to reveal the damage and fracturing mechanical behaviors of bimrock. The readers of this work can gain new insights into the meso-structural changes of bimrocks subjected to different stress paths. The book is expected to improve the understanding of the mesoscopic damage and fracturing mechanisms of bimrocks and can be helpful to predict the stability of rock structures where rock mass is subjected to complex loading conditions\"-- Provided by publisher.

Large deformation has always been a focus and difficult issue in the construction of deep-buried tunnels in squeezing rock. Previous studies mainly focused on the large deformation of medium and small span railway/highway tunnels in soft ground. However, there are limited researches on the large deformation control methods for large-span (three-lane) highway tunnels constructed in unfavorable geological environment. Based on the Lianchengshan Tunnel of the Baoji-Hanzhong expressway in Shaanxi Province, China, this paper studied the deformation behaviors and mechanical mechanisms of a large-span tunnel excavated in chlorite schist formation with single primary lining method and double primary lining method by in-situ test and numerical simulation. The achieved results indicate that the double primary lining method is much more effective than that of the single primary lining method in restraining the deformation of surrounding rock, and the maximum vertical displacement and horizontal convergence are reduced by 67% and 66%, respectively. The support method of double HK200b-type steel sets combined with large-diameter foot reinforcement bolt (FRB) and deep invert could effectively control the large deformation of the case tunnel, which effectively avoided the supporting structure failure, repeated clearance invasion and multiple reshaping work caused by the single primary lining method and conformed to the energy-saving construction concept of “no clearance interfering, no support reshaping” of tunnels in squeezing ground. Simulation analysis of surrounding rock deformation, supporting structure stress and plastic zone distribution was performed to evaluate the support effect of the two deformation-controlled methods. Finally, the deformation and stress characteristic curves of rock-support of the two deformation-controlled methods were established, which revealed the supporting mechanism of double primary linings for large-span tunnels in chlorite schist. The research results can provide a theoretical basis and practical reference for the large-deformation control of similar large-span tunnels in squeezing rock.

Subduction zones are critical sites for recycling of Li and B into the mantle. The way of redistribution of Li and B and their isotopes in subduction settings is debated, and there is a lack of detailed studies on Li and B partitioning between minerals of different types of eclogites and the host rocks of the eclogites. We present Li and B concentration data of minerals and Li and B whole-rock isotope data for low- T and high- T eclogites and their phengite schist host rocks from the Changning–Menglian suture zone, SW China. Omphacite controls the Li budget in both the low- T and high- T eclogites. Low- T eclogites have Li and δ 7 Li values (8.4–27.0 ppm, – 5.5 to + 3.2 ‰) similar to the phengite schists (8.7–27.0 ppm, – 3.8 to + 3.0 ‰), suggesting that Li was added to low- T eclogites from the phengite schists. In contrast, high- T eclogites have much lower δ 7 Li values (– 13.2 to – 5.8 ‰) than the phengite schists, reflecting prograde loss of Li or exchange with wall rocks characterized by low δ 7 Li values. Phengite and retrograde amphibole/muscovite are the major B hosts for low- T and high- T eclogites, respectively. The budgets and isotopic compositions of B in eclogites are affected by the infiltration of fluids derived from phengite schists, as indicated by eclogite δ 11 B values (– 15.1 to – 8.1 ‰) overlapping with the values of the phengite schists (– 22.8 to – 9.5 ‰). Lithium and B in eclogites are hosted in different mineral phases that may have formed at different stages of metamorphism, implying that the contents and isotopic compositions of Li and B may become decoupled during subduction-related fluid-mediated redistribution. We suggest a mineralogical control on the redistribution of Li and B in eclogites during subduction and the exchange of Li and B with the immediate wall rocks. The observed contrasting Li and B isotopic signatures in eclogites are likely caused by a fluid-mediated exchange with different types of wall rocks during both prograde metamorphism and exhumation.

Acoustic emission (AE) location technique and moment tensor analysis were used to evaluate the temporal–spatial evolution and damage of micro-cracks of schist during true triaxial compression and strain burst tests. The results show that the AE locations coincide with the macroscopic cracks for true triaxial compression while they are scattered during unloading strain burst tests. A shearing concentration occurs at the bottom of ejection position, but a tensile zone is located in the fracture plane of the ejection block. The ratios of shear and mixed-mode micro-cracks to total micro-cracks for true triaxial compression are both larger than those for strain burst. However, the strain burst has more tensile micro-cracks. Additionally, the damage caused by tensile micro-cracks for a strain burst is larger than that for a true triaxial compression. Moreover, for strain burst, the difference of damage between shear and tensile micro-cracks is in direct proportion to the loading rates after unloading.

The constitutive behavior of faults intervenes in virtually every aspect of the seismic phenomenon but is poorly understood, particularly regarding how effective normal stress affects the boundaries of the seismogenic zone. Here, we explore the mechanical properties of Pelona schist, Westerly granite, phyllosilicate‐rich gouge, gabbro, hornblende, lawsonite blueschist, montmorillonite, and smectite in hydrothermal conditions at various confining pressures and explain the laboratory observations with a physical model of fault friction. The thermobaric activation of healing and deformation mechanisms explains the boundaries of unstable slip as a function of slip‐rate, temperature, and effective normal stress for a given lithology. The constitutive law affords extrapolation of laboratory data in the conditions relevant to seismic cycles throughout the crust, explaining the focus of large earthquakes in collision, subduction, and continental and oceanic transform settings. Plain Language Summary An important goal of earthquake physics involves predicting the failure of rocks under the various physical conditions encountered during the seismic cycle. Here, we analyze mechanical data for Pelona schist, Westerly granite, phyllosilicate‐rich gouge, gabbro, hornblende, lawsonite blueschist, montmorillonite, and smectite that reveal how normal stress, temperature, and slip‐rate affect the frictional properties of rocks. We capture these effects consistently at constant coefficients with a physics‐based constitutive friction law. The boundaries of the seismogenic zone follow a thermobaric activation, whereby the transition temperature is a function of pressure. Increasing confining pressure may induce or inhibit velocity‐weakening behavior, depending on the constitutive properties controlling the healing and deformation mechanisms. The constitutive model provides an increasingly realistic representation of fault behavior during seismic cycles applicable to a wide range of tectonic contexts. Key Points The temperature boundaries of the seismogenic zone depend on confining pressure, implying a thermobaric activation of fault friction The model explains schist, granite, gabbro, hornblende, clays, and natural gouge friction evolution with velocity, temperature, and pressure The constitutive model provides a realistic representation of fault behavior during seismic cycles applicable to all tectonic contexts

Cuddapah Basin (CB) is an intracontinental, Proterozoic basin flanked by Eastern Dharwar Craton (EDC) in the west, Nellore Schist Belt (NSB) and Eastern Ghat Mobile Belt (EGMB) in the east, represents second largest Proterozoic basin of India. Gravity and magnetic surveys were carried out at the interface of Cuddapah Basin (CB) and Nellore Schist Belt (NSB) covering ~2880 km 2 area. Gravity map has brought out some distinct zones. The thrusted contact of NSB and Cuddapah sediments has been well delineated from the gravity map by NE–SW trending steep gradient of contours. Relatively high gravity values are observed over NSB in the southeastern part, moderately high values are observed over Cumbum Formation, but distinct low is observed over Baironkonda Formation. These gravity highs and lows are mainly the manifestation of basement characteristics and intrusives. The magnetic map shows two distinct domains, viz., moderate to low zone in the southern part, and moderate to high zone in the northern part. Regional gravity map suggests a change in basement characteristics from felsic to mafic from NW to SE. Presence of mafic basement may be representing EGMB group of rocks underneath the Cuddapah sediments at the eastern part of the study area. The joint gravity and magnetic modelling reveal varied nature of sedimentary units in terms of density and susceptibility and change in basement characteristic.

The Krishna region of south India comprises Eastern Ghats Mobile Belt (EGMB), Nellore Schist Belt (NSB) of Eastern Dharwar Craton (EDC) margin and Nallamalai Fold Belt (NFB) including Cuddapah Basin (CB) from east to west. The gravity surveys are carried out across it, so as to delineate the different litho-tectonic belts and salient structural features. The gravity data is processed to generate regional, residual and derivative maps along with three 2D gravity models. Two major gravity highs over the EGMB and NSB and a wide gravity low across the NFB, along with a linear gravity low representing as Transitional Zone (TZ) between these two highs are delineated. Two curvilinear steep gravity gradients between the NFB-NSB and NSB-EGMB are differentiated as Cuddapah Eastern Margin Thrust and Eastern Ghats Boundary Thrust along with a low angle Malakondasatram Thrust in the central part. The NSB comprises Eastern (EA) and Western (WA) arms of coeval different environmental facies of foreland and back-arc setups. The EA with intense gravity high due to a high-density layer at a depth of ~10 km is evidenced from 2D gravity model. The thickness of high-density layer (EA) gradually decreases towards westerly and wedges out below the WA suggesting the entire NSB as a single Late Archaean segment. The major linear gravity high of covered eastern part in Kavali–Nellore–Gudur region indicates the southern continuation of EGMB. The occurrence of thin unconformable high-grade schists in two doubly plunging structures and as tectonic lenses, including a major E–W folded erosional remnants in the low-medium grade late Archaean NSB domain are found as eastern continuation of Mesoproterozoic upper Cuddapah extensions at the EGMB front. These erosional remnants are reflected as isolated residual gravity lows in the west and as residual highs in overall EA of NSB in the east. The isolated relative highs and lows within the major low zone of NFB are linked to differential basement configuration due to superposed effects with the N–S non-cylindrical fold.

Dehydration reactions in the subducting slab liberate fluids causing major changes in rock density, volume and permeability. Although it is well known that the fluids can migrate and interact with the surrounding rocks, fluid pathways remain challenging to track and the consequences of fluid-rock interaction processes are often overlooked. In this study, we investigate pervasive fluid-rock interaction in a sequence of schists and mafic felses exposed in the Theodul Glacier Unit (TGU), Western Alps. This unit is embedded within metaophiolites of the Zermatt-Saas Zone and reached eclogite-facies conditions during Alpine convergence. Chemical mapping and in situ oxygen isotope analyses of garnet from the schists reveal a sharp chemical zoning between a xenomorphic core and a euhedral rim, associated to a drop of ~ 8‰ in δ18O. Thermodynamic and δ18O models show that the large amount of low δ18O H2O required to change the reactive bulk δ18O composition cannot be produced by dehydration of the mafic fels from the TGU only, and requires a large contribution of the surrounding serpentinites. The calculated time-integrated fluid flux across the TGU rocks is 1.1 × 105 cm3/cm2, which is above the open-system behaviour threshold and argues for pervasive fluid flow at kilometre-scale under high-pressure conditions. The transient rock volume variations caused by lawsonite breakdown is identified as a possible trigger for the pervasive fluid influx. The calculated schist permeability at eclogite-facies conditions (~ 2 × 10–20 m2) is comparable to the permeability determined experimentally for blueschist and serpentinites.

Transects across the Alpine Fault, New Zealand, show that thermal conductivity decreases and porosity increases with proximity to gouge comprising the principal slip surface. From cataclasite to gouge, thermal conductivity decreases from 2.12 ± 0.38 W m−1 K−1 to 1.38 ± 0.20 W m−1 K−1, and thermal diffusivity decreases from 0.97 ± 0.26 mm2 s−1 to 0.58 ± 0.16 mm2 s−1. Volumetric heat capacities are 2.15 ± 0.10 MJ K−1 m−3 in schist and mylonite, 2.28 ± 0.39 MJ K−1 m−3 in cataclasite, and 2.48 ± 0.54 MJ K−1 m−3 in gouge. Asperity‐scale flash heating occurs in cataclasites and gouges at critical weakening velocities of 0.21 and 0.13 m s−1, respectively. Bulk‐scale thermal pressurization occurs at slip distances of 0.1–0.7 m for cataclasite and <1 mm for gouge, less than the large‐magnitude earthquake slip distance of 6–10 m. Results show that thermally‐activated mechanisms in fault core cataclasite and gouge can weaken the Alpine Fault during seismic slip.