P-wave Velocity Research Articles

Compression and shear properties of OPC-MCA and basalt fiber cured shield waste mud after dry-wet cycles

The large-scale accumulation of shield waste mud (SWM) generated during urban subway construction is prone to cause potential environmental problems. A new low-carbon curing modified material, i.e., OPC-MCA, was firstly prepared to economically and environmentally treat SWM by partially replacing ordinary Portland cement (OPC) with a composite external admixture. Thereafter, laboratory curing experiments of SWM taken from the Jinan Jile Road Yellow River Tunnel were conducted by controlling OPC-MCA at a 20% dosage and basalt fiber (BF) at different dosages (0–1.05%). The appearance, mass and P-wave velocity of the cured specimens were characterized and the compression and shear strength tests were carried out. In addition, X-ray computed tomography (CT) and scanning electron microscope (SEM) analyses were performed to comprehensively assess the resistance of OPC-MCA cured SWM exposed to dry-wet (d-w) cycles with different BF dosages. The results confirmed that the optimal BF dosage for specimens that did not undergo d-w cycles was 0.45%, resulting in a 16.67% increase in compressive strength and a 51.56% increase in shear strength. The addition of BF enhanced the resistance of specimens to d-w cycles and reduced the deterioration rates of mass, P-wave velocity, and mechanical properties. The hydrophilic expansion property of clay minerals significantly contributed to strength degradation and pore deformation of cured SWM specimens. The development degree of microscopic cracks and pores in cured SWM specimens was significantly affected by both the dosage of BF and the number of d-w cycles. By incorporating BF, the volume and connectivity of cracks and pores were reduced, the formation of small-sized pores was decreased, and the expansion of cracks was inhibited throughout the cycling process.

An experimental study on mechanical properties and fracturing characteristics of granite under high-temperature heating and liquid nitrogen cooling cyclic treatment

Liquid nitrogen (LN2) fracturing is a promising technology for efficient development of hot dry rock reservoir geothermal resources. To investigate the cracking mechanism of LN2 on high-temperature granite, heating and LN2 cooling cyclic treatment were applied to granite samples. Based on Brazilian splitting test, and different methods were employed to describe the crack propagation and failure mechanism, including acoustic emission monitoring, laser profile scanning, and scanning electron microscopy. The results demonstrate that heating and LN2 cooling cyclic treatment deteriorates the mechanical properties of granite. Specifically, after 20 cycles, the average P-wave velocity of the samples decreases by 34%, with the amplitude of the waveform decreasing from 130 dB to 50 dB. Moreover, the uniformity and integrity of the waveform worsen after cyclic treatment. The tensile strength, peak strain, and brittleness index of granite samples decrease with cycle numbers. From 3 to 20 cycles, the absorbed energy of the samples reduces by 53%, with thermal damage reducing the energy storage limit. The cyclic cooling treatment of LN2 increases the surface roughness and width of crack of the samples, resulting in obvious plastic failure at both ends of the samples. Furthermore, the height parameter Sa and area ratio Sdr of the fracture surface increase by 53.8% and 69.5%, respectively, as the number of cycles increase from 3 to 20. Additionally, the fractal dimension of the granite samples increases from 2.155 to 2.181, indicating an increase in the complexity of the cross-section. Following heating and LN2 cooling cyclic treatment, the failure mode of granite changes from vertical splitting to shear failure, with decreased brittleness and increased plasticity and ductility.

Fracture response of thermal-treated granite under mode III loading: Through the edge-notched diametrically compressed disk specimen

The deep rock mass is subject to a high degree of coupling of geothermal and complex loading, and complex mechanical and hydraulic loading induces out-of-plane progression of primary fractures, culminating in the formation of pure mode III fractures. To study the impact of high temperatures on the fracture behavior of pure mode III, the edge-notched diametrically compressed (ENDC) granite discs were heat treated at different temperatures (25, 200, 400, 500, and 600 °C). Subsequently, comparative tests were conducted on both pure mode III and pure mode I fracture, using the digital image correlation (DIC) method and the acoustic emission (AE) technique. The results demonstrate that as the temperature increases, the mass and P-wave velocity decrease. Furthermore, under pure mode III loading, the ENDC sample exhibits higher peak loads and fracture toughness (KIIIc) compared to mode I (KIc), which shows a decrease of 60.72 % in KIIIc and 73.75 % in KIc after thermal treatment at 600 °C compared to the ambient conditions. Simultaneously, the elevated temperature augmentes the cumulative AE counts during loading. The variations in horizontal displacement elevation deviation (HDED) on either side of the deformation concentration zone indicate that the samples are more resistant to crack extension under pure mode III loading. In addition, a positive linear correlation is noted between KIIIc and KIc of ENDC disc samples. The relationship between rebound values and fracture toughness of ENDC discs was discussed, and discovered that the KIIIc and KIc values are quadratic with the rebound values tested by the complete disc. The discussed results may serve as an initial prediction of fracture toughness values.

Experimental study on evaluation of density, P-wave velocity, thermal conductivity, and thermal diffusion coefficient of granite after thermal treatments by using PCA

Temperature significantly influences the physical parameters of granite, resulting in variations in the rock's thermal conductivity. In order to examine the impact of changes in multiple physical parameters of granite at different temperatures on the thermal conductivity of rocks, Principal Component Analysis (PCA) was employed to determine the correlation between granite at different temperatures and various physical parameters, including density (ρ), P-wave velocity (P), thermal conductivity (KT), and thermal diffusion coefficient (KD). Utilizing the linear contribution rate, a single indicator 'y' was derived to comprehensively represent the thermal conductivity of rocks. Research findings indicate that within the temperature range of 150–450 °C, the 'y'-value is relatively high, signifying favorable thermal conductivity of the rock. Notably, longitudinal wave velocity demonstrates higher sensitivity to temperature changes compared to other physical parameters.

Statistical analysis of physico-mechanical parameters of sandstones occurring in orogenic settings

In northeastern Sicily (Italy), sandstone rock masses widely crop out as cover deposits over crystalline terrains belonging to the orogenic belt. Despite being part of the same geological formation, these sandstones are characterized by highly different features in terms of texture and physico-mechanical properties. This poses a scientific question on the possibility of tracing these rocks to a single statistical model, which could be representative of their main engineering geological properties. Therefore, it is worth investigating on the possible reasons of such differences, that should be searched either in the current geographical sandstone distribution or in the rock texture. For this study, sandstone samples were collected from different sites and were analyzed at both the hand and thin section scales. Three sandstone types were recognized, characterized by a different texture. Then, the laboratory characterization allowed estimating their main physico-mechanical and ultrasonic properties, such as porosity, density, mechanical strength, deformability, and ultrasonic velocities. The rock mechanical strength proved linked to the rock compactness and to the presence of lithic fragments, while pores and a pseudo-matrix between grains represent weakening features. Rock data were also statistically analyzed by grouping the specimens according to a geographical criterion, with respect to their sampling area, but no link was found between location and rock properties. Finally, with the aim of achieving mathematical laws that could be used to predict some rock properties from others, useful for practical purposes when dealing with such a high property variability, single and multiple regression analyses were carried out. Results show that the Uniaxial Compressive Strength, porosity, and P-wave velocity are the best predictors for a quick, indirect estimation of the main physico-mechanical parameters. The methodological approach developed for this research can be taken as reference to study other worldwide cases, involving rocks characterized by a wide range of physico-mechanical properties and covering large regional territories.

Evidence for Ultra-Low Velocity Zone Genesis in Downwelling Subducted Slabs at the Core–Mantle Boundary

Abstract We investigate broadband SPdKS waveforms from earthquakes occurring beneath Myanmar. These paths sample the core–mantle boundary beneath northwestern China. Waveform modeling shows that two ∼250 × 250 km wide ultra-low velocity zones (ULVZs) with a thickness of roughly 10 km exist in the region. The ULVZ models fitting these data have large S-wave velocity drops of 55% but relatively small 14% P-wave velocity reductions. This is almost a 4:1 S- to P-wave velocity ratio and is suggestive of a partial melt origin. These ULVZs exist in a region of the Circum-Pacific with a long history of subduction and far from large low-velocity province (LLVP) boundaries where ULVZs are more commonly observed. It is possible that these ULVZs are generated by partial melting of mid-ocean ridge basalt.

Usability of Trabzon stone as a natural building stone and aggregate

This study investigated the suitability of Trabzon stone, which is used as a building stone in many areas in and around Trabzon province, as an aggregate. It was found that the uniaxial compressive strength values of the samples taken from the quarry were 87-130 MPa, P-wave velocities were 5048-5642 m/s, density value was 2.58 g/cm3, apparent porosity values were 2.77-4.54%, water absorption values by weight were 1.04-1.78% and water absorption value by mass was 2.0%. Weight loss in the freeze-thaw test was 0.36%, weight loss in the wet-dry test was 0.22%, loss in the magnesium sulfate test was 13%, Los Angeles fragmentation resistance in coarse aggregate was 22%, abrasion resistance value was 18% and methylene blue value was 0.9%. When the results were analyzed, it was found that the mass water absorption rate and the magnesium sulfate test results were above the values required by the standards. Although these rocks are used as marble, it has been determined that the waste material is not suitable for use as ballast, crushed stone, stone fill, pere, and masonry for road and concrete construction. Despite this result, it is necessary to investigate the usability of materials from other marble quarries in the region as aggregates.

Magmatic underplating, plumbing system, and carbon-enhanced electrical conductivity in the Paraná Magmatic Province

The origin of large igneous provinces (LIPs) is still an enigma but likely involves magma storage and pathways spread throughout the crust, requiring indirect methods for its study. Here, we present 3-D resistivity models derived from the inversion of broadband (∼0.0001–3000 s) magnetotelluric data with 9–13 km lateral spacing in the central Paraná Magmatic Province, an expressive Early Cretaceous LIP in South America. Our results map in greater detail the previously interpreted LIP magma conduit and support, in contrast with seismological models, significant magmatic underplating to explain the observed conductivity near the LIP central axis. The potential axial lava feeder appears as a pair of crustal conductors (5–15 km; >0.1 S/m) parallel to the region of maximum thickness of both pre-volcanic sedimentary rocks and erupted tholeiitic basalts along an extension of at least 800 km. We propose the high conductivity is due to graphite films of precipitated carbon during the ascension of carbon-bearing fluids released by crystallizing magmas underplated at the base of the crust. The association of high conductivity with underplating is supported by high Vp/Vs ratios close to the conductive lineament, by a lower-crustal zone of high P-wave velocities at the basin axis attributed to mafic intrusions, and by a residual gravity high interpreted as gabbros underplated/intruded in the lower crust. Moreover, the conductive lineament is spatially associated with intracrustal high densities inferred from geoid inversion and upper-crustal high P-wave velocities. Early CO2 release during crystallization of underplated magma before eruption could explain the time gap between the Weissert ocean anoxic event and the volcanism. Our study advances in the controversial topic of magmatic intrusive components in the Paraná LIP with implications for LIP generation and paleo-climate studies.

Subslab ultra low velocity anomaly uncovered by and facilitating the largest deep earthquake

It is enigmatic that M8+ earthquakes can take place at depth greater than 600 km inside the slab, where the P-T conditions generally do not favor seismic slip rate (~m/s) on faults. Here we provide fresh insights to the initial rupture and mechanism of the Mw 8.3 Sea of Okhotsk earthquake by analyzing high-frequency (up to 0.8 Hz) teleseismic array data. We determine the relative location and timing of two early subevents, and the geometry and velocity perturbation of a nearby structure anomaly. We found a small-scale (~30 × 60 × 60 km) ultralow (−18 ± 2%) P-wave velocity anomaly located beneath the Pacific slab around the 660 km discontinuity. The volatile-bearing highly melted nature of the anomaly provides significant buoyancy, stressing the slab dramatically closer to the critical condition for thermal runaway weakening that allows the rupture to propagate beyond the metastable olivine wedge, forming M8+ events. Enormous velocity reduction urges for further mineral physics and geodynamic investigations.

Deformation microstructures of blueschists in Alpine Corsica, France, and implications for seismic anisotropy and the low-velocity layer in subducting oceanic crust

Understanding the deformation microstructures and seismic properties of blueschists is important for interpreting the seismic anisotropy at the top of subducting oceanic crust. The deformation microstructures and seismic properties of epidote blueschist, epidote-lawsonite blueschist, and lawsonite blueschist from Alpine Corsica, France, were studied using electron backscatter diffraction mapping and transmission electron microscopy. The crystal-preferred orientations (CPOs) of glaucophane show a strong maximum of the [001] axes aligned sub-parallel to the lineation. The maximum of the (010) poles of epidote is aligned sub-parallel to the lineation. The [001] axes of lawsonite are strongly aligned sub-normal to the foliation. Intracrystalline misorientation, dislocation, and occasional fragmentation of glaucophane indicate that glaucophane CPO was developed mainly by dislocation creep. The intracrystalline deformation features of epidote, such as subgrain boundaries and dislocations, indicate that the CPO of the epidote was formed by dislocation creep. In contrast, our data indicate that lawsonite CPO was developed by a combination of rigid-body rotation and dislocation creep with a minor effect of twinning. The P-wave anisotropy (AVp) and maximum S-wave anisotropy (max.AVs) of epidote blueschists (AVp = 12.3–16.9% and max.AVs = 6.53–11.75%) are higher than those of lawsonite blueschists. The seismic velocities of the blueschists are lower than those of mantle peridotites. The coexistence of epidote and lawsonite in the blueschist results in variations in seismic anisotropy and P-wave velocity in the whole rock, depending on the modal content of epidote and lawsonite. A high content ratio of epidote to lawsonite in blueschist produces strong P- and S-wave anisotropies of blueschist when the glaucophane content is more than ∼50%. The P-wave velocity of blueschist decreases proportionally with increasing epidote content. Our results indicate that the seismic properties of deformed blueschists contribute to the seismic anisotropy and the low-velocity layer in subducting oceanic crusts in subduction zones.

Evaluation of Cherts in Gumushane Province in Terms of Alkali Silica Reaction

Alkali–silica reaction (ASR) occurs when alkali oxides coming from the cement composition in concrete come together with reactive silica and moisture coming from the aggregate. Additional maintenance and repair costs caused by the development of ASR in concrete cause the cost to increase. However, thanks to the measures taken against ASR in the early period, it contributes to the creation of sustainable and durable concrete structures. The article investigated the usability of cherts with eight different chemical compositions as aggregates in ready-mixed concrete plants in Gümüşhane. Cherts have been investigated for alkaline reactivity and are intended to be used largely as a source for concrete plants. ASR length changes of the samples prepared according to ASTM C1260 standard were determined after 3, 7, 14, and 28 days of the curing period. Microstructural examination, ultrasonic P-wave velocity, and bending and compressive strength experiments supporting ASR were carried out. The obtained test results were compared between the reference (limestone) sample and each other, as well as with the values specified in the standards. The compressive and bending strength values of the samples increase depending on their ASR. It was observed that the crack structures and types increased depending on the increase in the crack values.

Post-collisional lithospheric delamination in eastern Iran, revealed by non-linear teleseismic tomography and residual topography

The Eastern Iranian Mountain Ranges (EIR) emerged as a consequence of the Late Cretaceous collision between the Afghan and Lut blocks. However, the response of the uppermost mantle to this collision remains enigmatic. Additionally, although petrological evidence suggests that post-collisional delamination is possible, it has not been conclusively identified in prior regional seismic imagery. This observation leads us to further explore this possibility using a dense seismic network. To gain insight into the geodynamic implications for eastern Iran and address knowledge gaps, we extensively investigated the seismic structure of the uppermost mantle beneath the EIR using a dense seismic network of 34 temporary stations, complemented by data from nine additional local permanent stations. By meticulously analyzing 6589 relative arrival time residuals from teleseismic records with favorable signal-to-noise ratios, we applied a non-linear tomography method to map P-wave velocity perturbations in a relative sense. Our tomographic images unveiled distinct instances of rapid high-velocity anomalies beneath low-velocity regions in the shallow mantle, suggesting the potential occurrence of lithospheric dripping, followed by subsequent asthenospheric upwelling. This observation offers a plausible explanation for the observed post-collisional magmatism over the Lut Block. Furthermore, to maintain the approximately 1.5-km positive residual topography across the EIR, beyond the influence of crustal properties, additional support from the hot and buoyant asthenosphere becomes crucial, particularly in the absence of a substantial lithospheric mantle.

Understanding the effects of permafrost degradation through a multiphysics approach

Permafrost is a multiphase porous media that can host matter in all three states (solid, liquid, and gas). The equilibrium between the states of matter within the pore space is largely driven by salinity, pressure, and temperature. The complex interactions between the different thermodynamic processes can lead to a complex pore system that is altered at each subsequent thaw and freeze cycle. The dynamic changes imposed on this porous media alter the mechanical and electrical properties of the samples. These changes can thus be quantified and monitored using ultrasonic and electrical resistivity measurements. The experimental results presented in this work document the impacts of a thawing event on unconsolidated quartz sand samples that are partially saturated with a brine solution. The electrical resistivity and ultrasonic data are acquired simultaneously throughout the experiment, and the spatiotemporal changes within the solid matrix are captured by time-lapse X-ray computed tomography (CT). A total of 39 different samples are investigated. The two independent variables chosen for this study are the grain size and the salinity of the brines. The results indicate a clear transition in electrical and elastic properties as the material in the pore space transitions between two different states. Further results indicate that these transitions are the result of the alteration of the pore network itself. In addition, the study of P-wave velocity, ice fraction, and X-ray CT of two different types of ice that coexist within the pore network is documented. Given the distinct impact of two different types of ice on this cryogenic porous media, it is imperative to thoroughly comprehend the existence of different ice types before undertaking the electroelastic investigation of permafrost.

Study on Acoustic–Electric Response Characteristics of Unsaturated Loess under Different Moisture Content

In order to study the characteristics of P-wave velocity and resistivity of loess with different moisture contents, low-field nuclear magnetic resonance, resistivity, and P-wave velocity tests were carried out on loess samples with 11 different moisture contents. The test results show that under the condition of the same dry density, the water in loess exists in two forms: bound water and free water. With the increase in moisture content, the water porosity of loess increases, the proportion of free water increases, and the resistivity gradually decreases and then tends to be stable, showing a power function relationship with moisture content. When the moisture content is less than 20%, the P-wave velocity decreases with the increase in the moisture content. In comparison, when the moisture content is greater than 20%, the wave velocity increases with the increase in the moisture content. A modified relation between wave velocity and moisture content and saturation is put forward, and the relationship expression between wave velocity and resistivity of loess is established. Finally, the reliability is verified by experimental data. The research results have a certain guiding significance for real-time monitoring of loess moisture content and engineering stability analysis in the loess area.

Deformation Behavior and Seismic Characteristics of Sandy Facies Opalinus Clay During Triaxial Deformation Under Dry and Wet Conditions

Unconsolidated, undrained triaxial deformation tests were performed on sandy facies Opalinus Clay at 50 MPa confining pressure to characterize the effect of water and microfabric orientation on the deformation behavior, mechanical properties, and P-wave velocity evolution. Dry and wet (≈ 8 and > 95% initial water saturation, respectively) samples with 12.6 ± 0.4 vol% porosity were deformed parallel and perpendicular to the bedding direction at a constant strain rate of 5 × 10–6 s−1. Dry samples revealed semi-brittle behavior and exhibited strain localization at failure, while deformation was more ductile at saturated conditions, promoting stable, slow faulting. Peak strength, Young’s modulus, and number of cumulative acoustic emissions decreased significantly for wet samples compared to dry samples; the opposite was observed for Poisson’s ratio. P-wave velocity anisotropy was significantly altered by differential stress, primarily due to the interplay between pore and fracture closure and stress-induced microcrack formation. For samples that were deformed perpendicular to bedding, we observed a reduction and reversal of P-wave velocity anisotropy with increasing differential stress, whereas anisotropy of parallel samples increased. The results suggest that water saturation reduces the pressure at the brittle-ductile transition and that the elastic properties and anisotropy of sandy facies Opalinus Clay can be significantly altered in an anisotropic stress field, e.g., adjacent to fault zones or tunnel excavations. Changes in elastic anisotropy are primarily controlled by the orientation between the pre-existing microfabric and the maximum principal stress direction, stress magnitude, and the degree of water saturation.

Anisotropy of Thermal Conductivity and P-wave Velocity in Sedimentary Soft Rocks and their Relationships with Porosity

Anisotropy of Thermal Conductivity and P-wave Velocity in Sedimentary Soft Rocks and their Relationships with Porosity

Strength Characteristics, Ultrasonic Wave Velocity, and the Correlation between Them in Clay Bricks under Dry and Saturated Conditions.

One of the methods used to discover the development of deterioration in bricks used as a construction material in a building is the monitoring of the bricks' strength characteristics over time. However, measuring the strength characteristics of bricks used in a building requires sampling for performing laboratory tests, which is not possible in some cases. As an alternative, ultrasonic wave velocity can be a useful, nondestructive tool for the indirect assessment of the strength characteristics of the bricks. In the present study, six different samples of clay bricks before utilization as construction materials in buildings located in Khorramabad City (Lorestan Province, western Iran) were collected. The mineralogical composition of the samples was studied using X-ray diffraction (XRD) analysis. As one common physical characteristic of the construction materials, the porosity (n) of the samples was measured. Next, the strength characteristics, including uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), and P-wave velocity (Vp), of the samples under dry and saturated conditions were determined. It was found that after the saturation of the samples, considerable decreases in the UCS and BTS and increases in the Vp occurred, respectively. By comparing the values of the UCS, BTS, and Vp of the samples under dry and saturated conditions, we found that the integrity loss for the UCS and BTS was higher than for the Vp. Results showed that the integrity loss of the UCS, BTS, and Vp was significantly affected by the n and clay mineral (CM) content of the samples. Considering the dry or saturated condition of the samples, there are good correlations with acceptable accuracy levels between the Vp and the UCS and BTS, with coefficients of determination (R2) varying from 0.95 to 0.98. Consequently, our findings showed that establishing UCS and BTS predictive equations for bricks before their use as a construction material can be a worthy, practical tool for monitoring the deterioration of bricks over time after their utilization in a building.

Comparison of surface-wave techniques to estimate S- and P-wave velocity models from active seismic data

Abstract. The acquisition of seismic exploration data in remote locations presents several logistical and economic criticalities. The irregular distribution of sources and/or receivers facilitates seismic acquisition operations in these areas. A convenient approach is to deploy nodal receivers on a regular grid and to use sources only in accessible locations, creating an irregular source–receiver layout. It is essential to evaluate, adapt, and verify processing workflows, specifically for near-surface velocity model estimation using surface-wave analysis, when working with these types of datasets. In this study, we applied three surface-wave techniques (i.e., wavelength–depth (W/D) method, laterally constrained inversion (LCI), and surface-wave tomography (SWT)) to a large-scale 3D dataset obtained from a hard-rock site using the irregular source–receiver acquisition method. The methods were fine-tuned for the data obtained from hard-rock sites, which typically exhibit a low signal-to-noise ratio. The wavelength–depth method is a data transformation method that is based on a relationship between skin depth and surface-wave wavelength and provides both S- and P-wave velocity (Vs and Vp) models. We used Poisson's ratios estimated through the wavelength–depth method to constrain the laterally constrained inversion and surface-wave tomography and to retrieve both Vs and Vp also from these methods. The pseudo-3D Vs and Vp models were obtained down to 140 m depth over an area of approximately 900 × 1500 m2. The estimated models from the methods matched the geological information available for the site. A difference of less than 6 % was observed between the estimated Vs models from the three methods, whereas this value was 7.1 % for the retrieved Vp models. The methods were critically compared in terms of resolution and efficiency, which provides valuable insights into the potential of surface-wave analysis for estimating near-surface models at hard-rock sites.

Thermal-Induced Microstructure Deterioration of Egyptian Granodiorite and Associated Physico-Mechanical Responses.

Mineral transformations often induce microstructural deteriorations during temperature variations. Hence, it is crucial to understand why and how this microstructure weakens due to mineral alteration with temperature and the correlated physical and mechanical responses. Therefore, in this study, physical, chemical, thermal, petrographic, and mechanical analyses were carried out to comprehend better the thermal behaviors of Egyptian granodiorite exposed to temperatures as high as 800 °C. The experimental results indicate that the examined attributes change in three distinct temperature phases. Strength zone (up to 200 °C): During this phase, the temperature only slightly impacts the granodiorite mass loss and porosity, and the P-wave velocity and E slightly decrease. However, the rock structure was densified, which resulted in a minor increase in strength. After that, the transition zone (200-400 °C) was distinguished by the stability of most studied parameters. For instance, mass and porosity did not significantly alter, and the uniaxial compressive strength steadily increased with an axial failure mode. When the temperature rises, transgranular cracks cause the P-wave velocity and elastic modulus to decrease moderately. The decay zone started after 400 °C and continued to 800 °C. This zone is characterized by complicated factors that worsen the granodiorite properties, lead to color shift, and produce a shear failure mode. The properties of granodiorite became worse because of chemical reactions, structural and crystal water evaporation, rising thermal expansion coefficient variation, and quartz inversion at 575 °C (α to β, according to the differential thermal analysis). Thermal damage greatly affected granodiorite's physical and mechanical properties and microstructure at 800 °C. As a result, UCS measurements were extremely small with a complex failure pattern, making Vp and E unattainable.

Probabilistic characterisation of rock mass deformation modulus from P-wave velocity based on information criteria

ABSTRACT Determination of rock mass deformation modulus (Erm ) is an important but very challenging task in rock mechanics and rock engineering. Direct measurements of Erm by in-situ tests are expensive, time-consuming, and sometimes even impossible. Since the nondestructive and easy geophysical method is commonly used to measure the P-wave velocity (Vp ) in the field, the study has developed an empirical correlation between Erm and Vp based on 834 collected datasets by considering both inherent and transformation uncertainties. The information criteria are employed to select the best model for deriving a general empirical correlation. The maximum likelihood estimation (MLE) method and computational intelligence techniques like particle swarm optimisation (PSO), artificial bee colony (ABC), and differential evolution (DE) algorithms are used to specify the incorporated parameters of each candidate model. Based on the derived general empirical equation, a Bayesian equivalent sample approach using Markov Chain Monte Carlo (MCMC) simulation is applied to conduct probabilistic characterisation of Erm by combining prior knowledge and project-specific observed Vp data. Comparative studies of the results from theory and in-situ measured Erm values suggest that the proposed method is effective and validate the applicability of the derived general empirical correlation.