Bulletin of Engineering Geology and the Environment最新文献

This experimental and numerical study examines the propagation of dynamic compressive stress waves within geological lithological layers. In contrast to conventional split Hopkinson pressure bar (SHPB) systems, this research employed a custom-designed electromagnetic pendulum impact testing (EPIT) system. The electromagnetically controlled EPIT system was developed to allow precise and consistent repetition of impact tests at varied speeds. The EPIT system was integrated into a modified SHPB apparatus, featuring an extended length of up to 3 m and using rock bars exclusively, rather than conventional steel bars. Three types of modified SHPB configurations-single-rock-bar, double-rock-bar, and triple-rock-bar systems-were analyzed. Testing was conducted on limestone, marble, and sandstone specimens, each measuring 1 m in length and 0.05 m in diameter. Results indicate that sandstone exhibits the highest peak compressive strain and attenuation rate along the propagation path, distinguishing it from the behaviors observed in limestone and marble. The dynamic response characteristics of each rock layer are affected by the source of dynamic load, the inherent properties of the rock layer, and the properties of subsequent layers. A significant negative correlation was found between the average compressive strain amplification ratio and density ((rho )) ratio (( R = -0.92 )). Ratios of elastic modulus (( E )), P-wave velocity ((v_p)), and wave impedance ((Z_w)) also notably influence compressive strain amplification (( R = -0.85, -0.86, ) and ( -0.85 ), respectively). The UCS ratio has the least impact on strain amplification (( R = -0.7 )). Additionally, the pattern of stress attenuation was effectively described using a combination of power and Gaussian functions.

Desiccation crack patterns are commonly observed in natural and engineered soils and provides preferential pathways for moisture infiltrating into the soil. Cracks occur easily in soil when moisture is lost due to desiccation. Crack formation and development are closely related to moisture content and have a marked impact on the soil deformation characteristics and hydraulic properties. However, the critical moisture content below which desiccation cracks appear in the soil is usually determined by experiment because there is a lack of research on theoretical calculation models. Therefore, a theoretical calculation model is proposed to calculate the critical moisture content, and a parameter, (lambda), based on the following relationships: between soil grain size and suction, between suction and tensile strength, and between soil cracking and tensile strength. The critical moisture content values of different grain compositions were calculated and compared with laboratory experiments of desiccation crack. The critical moisture content of the granite residual soil is between 20% (50% liquid limit) and 30% (75% liquid limit). The presented model provides a means to estimate the critical moisture content of crack formation from soil desiccation using basic soil properties. This method can estimate the characteristics of soil desiccation cracks under extreme weather condition.

Oil storage in abandoned coal mines can effectively alleviate the shortage of space for oil reserves, however, the mechanical effects of oil storage on the mining envelope (sandstone) need to be further explored. To clarify the weakening effect of crude oil saturation on sandstone at different reservoir depths, triaxial mechanical tests of oil-saturated sandstone under different confining pressures were carried out on the GCTS rock mechanics testing machine. The mechanical properties, energy dissipation characteristics, and crack extension evolution process of oil-saturated sandstone were obtained. The results show that the softening coefficient of oil-saturated sandstone has a change rule of increasing and then decreasing with the increase of confining pressure. The oil-saturated treatment does not change the energy evolution process of the sandstone, but it has a greater influence on the energy parameters. The number of AE events and the released energy of oil-saturated sandstone is lower than that of natural sandstone at different confining pressures. However, due to the influence of the Kaiser Effect, the difference gradually decreases with the increase of the confining pressure, which macroscopically shows that the increase of the confining pressure moderates the effect of oil saturation on the energy parameters and crack extension of sandstone. In engineering applications, this research provides a theoretical basis for understanding the mechanical changes in surrounding rock at different oil storage depths in abandoned mine rock channels. Additionally, it offers scientific recommendations for selecting optimal depths for oil storage in rock tunnels.

Strong earthquakes in Chile are often associated with cascading hazards, such as ground shaking, liquefaction, tsunamis, and coseismic landslides. This study set recommendations for preparing earthquake-induced landslide inventories and developing and reporting an updated comprehensive earthquake-triggered landslides inventory of the 2007 M_w 6.2 shallow crustal Aysén earthquake. 781 landslides were re-mapped over a total area of c.1,350 km², based on unified earthquake-triggered landslide mapping criteria. The total landslide volume is c. 122.3 Mm³. 18% of earthquake-induced landslides were concentrated within 0–1 km of seismic faults, and 55% within 0–5 km. In addition, 53% of the landslides started in the upper quarter of the slope, while over 86% started in the upper half, which suggests that larger ground motions due to topographic site effects influenced the triggering of landslides during the shallow crustal earthquake. Hence, the distance to the rupture plane of faults is a first-order factor in the distribution of landslides together with topographic amplification site effects.

The freeze-thaw cycle poses a significant threat to foundations and roadbeds in seasonally frozen regions. This article conducts model experiments to analyze changes in the temperature field, water migration patterns, and settlement deformation characteristics of sand-gravel replacement foundations during freeze-thaw cycles. The experimental findings indicate that the low-temperature zone primarily exists within the sand-gravel replacement layer at the base of the slope. As the number of freeze-thaw cycles increases, the freezing depth of the sand-gravel replacement layer continues to rise. During the cooling phase, changes in soil volume moisture content result from self-weight and water migration during freezing. With an increase in the number of freeze-thaw cycles, the moisture content of external measurement points on the embankment rises at the end of the freezing period, whereas the moisture content of internal measurement points decreases. At the end of the thawing phase, measurement point 6 experiences an increase in moisture content due to the upward migration of water in the lower soil layer, while other measurement points exhibit reduced moisture content. The foundation’s settlement deformation exhibits a horizontal “tilted” shape, with cumulative settlement amounts and settlement deformation rates determined at various positions. These results suggest that the settlement deformation tends to stabilize one month after the completion of embankment filling construction. The maximum freezing depths at the left and right slope toe positions are 1 m and 1.2 m, respectively. Furthermore, the maximum frost heave at the slope toe position is less than the maximum thawing settlement, illustrating the irreversible soil deformation following freeze-thaw cycles.

Non-bedding fissures are common internal defects in layered slopes and often exert control over the slope's stability. In this study, a research on the failure mechanism of anti-dip bedding rock slopes (ABRSs) with two sets of non-bedding fissures was conducted based on fracture mechanics theory and the ABRSs cantilever beam model. Through centrifuge test, the rationality of this calculation method was verified, and the instability evolution mechanism of anti-dip bedding rock slopes containing internal defects was investigated. The research findings demonstrate that the instability of ABRSs containing non-bedding fissures goes through several stages, including tension of the rear rock layers, reverse bending of the rock layers, formation of the main fracture plane, and secondary failure. The initiation pattern of rock bridges between fissures significantly affects the post-failure deformation of rock layers. Additionally, tensional failure at gentle-dip fissures, occurring under shear action, is the main cause for inducing reverse bending of the fractured rock mass. This eventually leads to the formation of a stepped main fracture plane, resulting in the evolution of the slope into a reverse bending collapse zone and a block-reverse bending collapse zone. At approximately one-third of the slope height, the residual sliding force of the rock layers reaches its maximum, which is also the location where fissure deformation is most prominent and the stress situation is most complex. Moreover, the stability of ABRSs containing non-bedding fissures is more sensitive to the internal friction angle between rock layers, the length of non-bedding fissures, and the angle between fissures and rock layers.

In this paper, we present the construction of a geomechanical conceptual model for Permian–Triassic reservoirs of the Persian Gulf, achieved through a comprehensive comparison between geological facies, wireline data, and geomechanical parameters. Integrating geological and geomechanical data enabled the spatial distribution of key geomechanical parameters and the development of a conceptual model. This model offers valuable insights into the mechanical behavior of the various parts of the reservoir. Our database includes petrographical analysis of 1577 thin sections of 403 m of cores, routine core analysis, wireline logs, and geomechanical data in one well. Also, wireline logs from 6 other wells were used for correlation. Thin section studies showed 12 microfacies that have been deposited in a ramp depositional environment. Geomechanical data including Young modulus (E), Poisson ratio modulus (ϑ), shear modulus (G), bulk modulus (K), Schmidt hammer, and unconfined compressive stress (UCS), compared with geological and petrographical results. Electrofacies were constructed with the use of wireline log data. The incorporation of geomechanical data allowed for the construction of five geomechanical facies. The geomechanical features exhibit a progressive increase from one to five, indicating an inverse relationship with the reservoir quality of the electrofacies. Geomechanical units were defined by grouping similar geomechanical facies. Then, a relationship was established between geomechanical units and sea level changes. Subsequently, these units were correlated with sequence stratigraphic units and matched across the other six wells through the utilization of wireline logs. The spatial distribution of geomechanical units was determined by establishing their correlation with both geological facies and sequence stratigraphic units. Each geomechanical unit corresponds to the same depth interval of a systems tract belonging to a third-order sequence and a complete fourth-order sequence. This enabled us to detect and analyze the variations in the distribution patterns of geomechanical properties across the study area.

The failure behavior of rocks is complex due to the existence of random microscopic defects. This paper presents a new statistical damage model based on the modified Hoek-Brown criterion, i.e., the Pan-Hudson criterion, for predicting the mechanical characteristics of quasi-brittle rocks under compression, and demonstrated its predictive performance for medium-strong rocks. The lognormal distribution is incorporated to validate and reveal the statistical nature of internal microscopic defects. Its effectiveness in describing microscopic defects evolution is highlighted by comprehensive discussions on characteristic distribution parameters, which are rigorously derived. The degradation effects of microscopic defects on macroscopic mechanical responses are reflected by establishing the quantitative relation between damage variables and compressive strength. To validate the proposed model, a series of triaxial compression tests on sandstone are conducted. The peak strength and quasi-brittle post-peak behavior under various confining pressures are well captured. Sensitivity analyses on mechanical and characteristic distribution parameters are also carried out to develop an intuitive understanding of how the introduced modifications affect the mechanical responses. Finally, the deviatoric stress-axial strain curves were compared between our testing data of limestone and previous study. The advantages in capturing peak intensity and simulating the post-peak behavior of the proposed model is emphasized.

The Fenwei Basin has developed more than 600 ground fissures of different scales, with the Ground Fissures on Marginal Mountainous Region (GFMMR) in the Basin cause the most severe damage. However, there is currently limited research on the common characteristics of GFMMR, and the formation mechanisms are not yet clear. This study utilizes geological surveys, trenching, drilling, geophysical exploration, interferometric synthetic aperture radar (InSAR), and numerical simulation, found that the GFMMR develop on the hanging wall of the marginal mountainous faults, with their strikes generally consistent with these faults, and the failure pattern of these ground fissures that near the mountain is primarily shear failure, gradually transitioning to tension failure at the distal end. Profile results show clear synsedimentary fault characteristics, and these ground fissures are connected to deep-seated faults. This study reveals that the formation mechanisms of the GFMMR in the Fenwei Basin involve two aspects: fault control and hydrodynamic triggering. The extensional stress in the NW–SE direction of the Basin, combined with the counterclockwise rotation of the Ordos block, leads to the extensional creep of the marginal mountainous faults, further controlling the exposure locations and activity intensity of the GFMMR. Human overpumping of groundwater induces uneven subsidence of the stratum, forming a series of subsidence funnels on the surface, which exacerbates the rupture and expansion of ground fissures while also accelerating their exposure through water erosion caused by rainfall. This study has essential reference value for disaster prevention and reduction of ground fissures in the Fenwei Basin.