To investigate the effects of the maximum principal stress direction (theta) and cross- shape on the failure characteristics of sandstone, true-triaxial compression experiments were conducted using cubic samples with rectangular, circular, and D-shaped holes. As theta increases from 0 degrees to 60 degrees in the rectangular hole, the left failure location shifts from the left corner to the left sidewall, the left corner, and then the floor, while the right failure location shifts from the right corner to the right sidewall, right roof corner, and then the roof. Furthermore, the initial failure vertical stress first decreases and then increases. In comparison, the failure severity in the rectangular hole decreases for various theta values as 30 degrees > 45 degrees > 60 degrees > 0 degrees. With increasing theta, the fractal dimension (D) of rock slices first increases and then decreases. For the rectangular and D-shaped holes, when theta = 0 degrees, 30 degrees, and 90 degrees, D for the rectangular hole is less than that of the D-shaped hole. When theta = 45 degrees and 60 degrees, D for the rectangular hole is greater than that of the D-shaped hole. Theoretical analysis indicates that the stress concentration at the rectangular and D-shaped corners is greater than the other areas. The failure location rotates with the rotation of theta, and the failure occurs on the side with a high concentration of compressive stress, while the side with the tensile and compressive stresses remains relatively stable. Therefore, the fundamental reason for the rotation of failure location is the rotation of stress concentration, and the external influencing factor is the rotation of theta. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Local site effects play a vital role in determining the level of structural damage to the structures built on soil. Therefore, correctly determining the underground layer structure and its physical characteristics in the lateral and vertical directions is essential for the geotechnical model. More information and more accurate results will be obtained if the geotechnical model is evaluated multidisciplinary together with geophysical studies, not only based on drilling results. For this purpose, vertical electric sounding, seismic refraction, microtremor, and mechanical drilling techniques were applied within the scope of geotechnical studies in the & Idot;neg & ouml;l district of Bursa. The methods were evaluated together, and the geotechnical cross-sections of the underground were interpreted. In addition, microzonation maps determined from Geophysical parameters were created in the study area. These maps, geotechnical cross-sections, and microtremor data evaluation results predicted how the study area's buildings and soils would behave under dynamic forces such as earthquakes. As a result, the soils in the study area were mainly saturated with water and had weak strength. Existing or newly constructed engineering structures on such soils are predicted from microzonation maps that will damage both the soils and the buildings in a seven-magnitude earthquake.

Karst fracture-cavity carbonate reservoirs, in which natural cavities are connected by natural fractures to form cavity clusters in many circumstances, have become significant fields of oil and gas exploration and exploitation. Proppant fracturing is considered as the best method for exploiting carbonate reservoirs; however, previous studies primarily focused on the effects of individual types of geological formations, such as natural fractures or cavities, on fracture propagation. In this study, true-triaxial physical simulation experiments were systematically performed under four types of stress difference conditions after the accurate prefabrication of four types of different fracture-cavity distributions in artificial samples. Subsequently, the interaction mechanism between the hydraulic fractures and fracture-cavity structures was systematically analyzed in combination with the stress distribution, cross-sectional morphology of the main propagation path, and three-dimensional visualization of the overall fracture network. It was found that the propagation of hydraulic fractures near the cavity was inhibited by the stress concentration surrounding the cavity. In contrast, a natural fracture with a smaller approach angle (0 degrees and 30 degrees) around the cavity can alleviate the stress concentration and significantly facilitate the connection with the cavity. In addition, the hydraulic fracture crossed the natural fracture at the 45 degrees approach angle and bypassed the cavity under higher stress difference conditions. A new stimulation effectiveness evaluation index was established based on the stimulated reservoir area (SRA), tortuosity of the hydraulic fractures (T), and connectivity index (CI) of the cavities. These findings provide new insights into the fracturing design of carbonate reservoirs. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

Compared with circular, arched, and pipe-arched soil-steel structures, box-type soil-steel structures (BTSSSs) have the advantages of high cross- utilization and low cover depth. However, the degree of influence of the crown and haunch radii on the mechanical performance of BTSSSs is still unclear. Therefore, two full-scale BTSSS models with a span of 6.6 m and a rise of 3.7 m but with different crown and haunch radii were established, and the mechanical properties during backfilling and under live load were tested. Afterward, 2D finite element models (FEMs) were established using the ABAQUS 2020 software and verified using the test data. The influence of cross- geometric parameters on mechanical performance was analyzed by using the FEM, and a more accurate formula for calculating the bending moment during backfilling was proposed. The results show that the BTSSS with a smaller crown radius has a stronger soil-steel interaction, which promotes more uniform stress on the structure and makes the structure have smaller relative deformations, bending moments, and earth pressure. The span and arch height greatly influence the bending moment and deformation of the structure. Based on the CHBDC, the crown and haunch radii were included in the revised calculation formula.

The climate models of the Intergovernmental Panel on Climate Change list black carbon (BC) as an important contributor to global warming based on its radiative forcing (RF) impact. Examining closely these models, it becomes apparent that they might underpredict significantly the direct RF for BC, largely due to their assumed spherical BC morphology. Specifically, the light absorption and direct RF of BC agglomerates are enhanced by light scattering between their constituent primary particles as determined by the Rayleigh-Debye-Gans theory interfaced with discrete dipole approximation and recent relations for the refractive index and lensing effect. The light absorption of BC is enhanced by about 20% by the multiple light scattering between BC primary particles regardless of the compactness of their agglomerates. The resulting light absorption agrees very well with the observed absorption aerosol optical depth of BC. ECHAM-HAM simulations accounting for the realistic BC morphology and its coatings reveal high direct RF = 3-5 W/m2 in East, South Asia, sub-Sahara, western Africa, and the Arabian peninsula. These results are in agreement with satellite and AERONET observations of RF and indicate a regional climate warming contribution by 0.75-1.25 degrees C, solely due to BC emissions.

The estimates of radiative forcing of black carbon (BC) remain great uncertainty, largely due to variations in the absorption enhancement of BC by mixing with organic and inorganic coatings in ambient aerosols. We applied a two-step solvent treatment method that experimentally removed coating materials in aerosol samples to determine the BC absorption enhancement. Aerosol samples were collected at Mt. Tai and a severely polluted urban area (Jinan) in North China Plain (NCP). The mass absorption cross- (MAC) of BC aerosols was determined before and after the coating removal. Three thermal-optical protocols, NIOSH, EUSAAR and IMPROVE, were tested for determining of BC mass and MAC. The EUSAAR protocol gave the optimal values of BC mass concentrations and MAC. The MAC for decoated BC was 3.8 +/- 0.9 and 3.8 +/- 0.1 m(2) g(-1) (Average and 1SD) at 678 nm wavelength at the urban area and Mt. Tai, respectively, and it was consistent with the theoretical calculation for pure BC. The MAC for ambient aerosol samples was enhanced to 7.4 +/- 2.6 and 7.8 +/- 2.7 m(2) g(-1) at Jinan and Mt. Tai respectively. Non - BC coatings could enhance the MAC (E-MAC) by a factor of 2 at both the polluted urban area and mountain summit. The light absorption of BC may be rapidly enhanced from air pollution in severely polluted area, and then it remains relatively constant for aged aerosols at Mt. Tai. Climate model is recommended for amplifying BC absorption by a factor of 2 in East Asia and other areas with intense industrialization and urbanization. (C) 2018 Elsevier B.V. All rights reserved.

A reliable assessment of the optical properties of atmospheric black carbon is of crucial importance for an accurate estimation of radiative forcing. In this study we investigated the spatio-temporal variability of the mass absorption cross- (MAC) of atmospheric black carbon, defined as light absorption coefficient (sigma(ap)) divided by elemental carbon mass concentration (m(EC)). sigma(ap) and m(EC) have been monitored at supersites of the ACTRIS network for a minimum period of one year. The 9 rural background sites considered in this study cover southern Scandinavia, central Europe and the Mediterranean. sigma(ap) was determined using filter based absorption photometers and m(EC) using a thermal-optical technique. Homogeneity of the data-set was ensured by harmonization of all involved methods and instruments during extensive intercomparison exercises at the European Center for Aerosol Calibration (ECAC). Annual mean values of sigma(ap) at a wavelength of 637 nm vary between 0.66 and 1.3 Mm(-1) in southern Scandinavia, 3.7-11 Mm(-1) in Central Europe and the British Isles, and 2.3-2.8 Mm(-1) in the Mediterranean. Annual mean values of mEC vary between 0.084 and 0.23 mu g m(-3) in southern Scandinavia, 0.28 -1.1 in Central Europe and the British Isles, and 0.22-0.26 in the Mediterranean. Both sigma(ap) and mEC in southern Scandinavia and Central Europe have a distinct seasonality with maxima during the cold season and minima during summer, whereas at the Mediterranean sites an opposite trend was observed. Annual mean MAC values were quite similar across all sites and the seasonal variability was small at most sites. Consequently, a MAC value of 10.0 m(2) g(-1) (geometric standard deviation = 133) at a wavelength of 637 nm can be considered to be representative of the mixed boundary layer at European background sites, where BC is expected to be internally mixed to a large extent. The observed spatial variability is rather small compared to the variability of values in previous literature, indicating that the harmonization efforts resulted in substantially increased precision of the reported MAC. However, absolute uncertainties of the reported MAC values remain as high as +/- 30-70% due to the lack of appropriate reference methods and calibration materials. The mass ratio between elemental carbon and non-light-absorbing matter was used as a proxy for the thickness of coatings around the BC cores, in order to assess the influence of the mixing state on the MAC of BC. Indeed, the MAC was found to increase with increasing values of the coating thickness proxy. This provides evidence that coatings do increase the MAC of atmospheric BC to some extent, which is commonly referred to as lensing effect. (C) 2016 The Authors. Published by Elsevier Ltd.