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This study investigated the sidewall rockburst characteristics of highly stressed circular tunnel subjected to impact loads resulting from rock blasting or other mining-related dynamic disturbances, aiming at exploring the influence of vertical prestress and dynamic load on sidewall rockburst. Using a biaxial Hopkinson pressure bar (BHPB) system, we studied the sidewall rockburst of a circular tunnel by applying various prestresses (horizontal and vertical static stresses) to a sand prefabricated circular hole specimen, followed by impact loads. The real-time process and strain field of the sidewall rockburst around the specimen were tracked by the high-speed camera and digital image correlation (DIC). The tests reveal that the sidewall rockburst process can be summarized as: calm stage, slab buckling and spalling stage, rock slabs ejection stage, and V-shaped notch formation stage. Furthermore, the sidewall rockbursts exhibit typical dynamic tensile failure. The mechanism of sidewall rockburst under the coupled static-impact loads was summarized, i.e. the static prestress determines the initial stress and strain distribution, and the vertical prestress influences the affected range and strain values of the strain concentration zone; the impact load disrupts the original static stress equilibrium, inducing alterations in the stress and strain of the surrounding rock and triggering sidewall rockburst.

Rockburst has always been a challenge for the safe construction of deep underground engineering. This study investigated the rockburst characteristics in highly-stressed D-shape tunnels under impact loads from rock blasting and other mining-related dynamics disturbances. The biaxial Hopkinson pressure bar was utilized to apply varying biaxial prestress and the same impact loads to cube specimens with D-shape hole. High-speed camera and digital image correlation (DIC) were used to capture the failure process and strain field of specimen. The test results demonstrate that the D-shape hole specimen experience rockburst under coupled static stress and impact load. Under this circumstance, the rockburst mechanism of the D-shaped hole specimens involves spalling in sidewall induced by impact load, indicating dynamic tensile failure. The high static prestress provides the initial stress field, while the impact load disrupts the stress equilibrium, result in the stress or strain concentration in the sidewall of the D-shape hole, inducing rockburst. Moreover, the rockburst process can be divided into (1) calm stage, (2) crack initiation, propagation, and coalesce stage, (3) spalling stage and (4) rock fragments ejection stage. Impact load triggers rockburst occurrence, while vertical stress further determines the rockburst characteristics. The influence range and magnitude of strain concentration zone and displacement deformation of the tunnel surrounding rock increases with increasing vertical stress, thus inducing more severe rockburst.

Abstract Background Using winter fallow fields for plant forage is important to ensure food security. Forage triticale (× Triticosecale) has higher yields than other available forage crops and can be planted widely in winter fallow fields. Recently, the planted area of forage triticale in Shanxi Province, China, has exceeded 3500 ha; however, problems such as low farmer willingness to plant (WTP) winter forage still remain. Methods A total of 219 farmers were surveyed in Taiyuan, Lvliang, and Jinzhong. We analyzed the factors influencing farmer WTP forage triticale, focusing on personal, family, land, and cognition characteristics. We used a binary logistic regression model to quantify the influence of various factors on farmer behavior and conducted a robustness check and heterogeneity analysis. Results “Age” was negatively correlated with farmer WTP—farmers 50 years of age and older showed less WTP. “Land lease situation” was also negatively correlated with WTP. Factors that positively correlated with WTP were “land areas,” “raising of livestock,” “size of labor force,” and “development prospect.” Conclusions Many farmers are over 50 years of age, land lessors, and have low WTP winter forage. Farmers who raise livestock and have large labor forces, huge land areas, and good cultivation prospects have a high WTP. This study identifies the factors influencing farmers' WTP to assist in the development of the forage triticale industry in the study region, improving land resource utilization and efficiency. The findings are likely to have wider relevance and application.

Grassland degradation is a serious ecological issue in the farming–pastoral ecotone of northern China. Utilizing native grasses for the restoration of degraded grasslands is an effective technological approach. Leymus secalinus is a superior indigenous grass species for grassland ecological restoration in northern China. Therefore, the excavation of potential distribution areas of L. secalinus and important ecological factors affecting its distribution is crucial for grassland conservation and restoration of degraded grasslands. Based on 357 data points collected on the natural distribution of L. secalinus, this study employs the jackknife method and Pearson correlation analysis to screen out 23 variables affecting its spatial distribution. The MaxEnt model was used herein to predict the current suitable distribution area of L. secalinus and the suitable distribution of L. secalinus under different SSP scenarios (SSP1-26, SSP2-45, and SSP5-85) for future climate. The results showed the following: (1) Mean diurnal temperature range, annual mean temperature, precipitation of the wettest quarter, and elevation are the major factors impacting the distribution of L. secalinus. (2) Under the current climatic conditions, L. secalinus is mainly distributed in the farming–pastoral ecotone of northern China; in addition, certain suitable areas also exist in parts of Xinjiang, Tibet, Sichuan, Heilongjiang, and Jilin. (3) Under future climate change scenarios, the suitable areas for L. secalinus are generally the same as at present, with slight changes in area under different scenarios, with the largest expansion of 97,222 km2 of suitable area in 2021–2040 under the SSP1-26 scenario and the largest shrinkage of potential suitable area in 2061–2080 under the SSP2-45 scenario, with 87,983 km2. Notably, the northern boundary of the middle- and high-suitability areas is reduced, while the northeastern boundary and some areas of Heilongjiang and Jilin are expanded. The results of this study revealed the suitable climatic conditions and potential distribution range of L. secalinus, which can provide a reference for the conservation, introduction, and cultivation of L. secalinus in new ecological zones, avoiding the blind introduction of inappropriate habitats, and is also crucial for sustaining the economic benefits associated with L. secalinus ecological services.

A spherical weathering body, also called a boulder, is an element of complex geological strata and presents a significant challenge to tunnelling by a tunnel-boring machine (TBM). In this study, ground-based drilling and blasting were used to precondition boulders. To determine the specific charge needed for preconditioning blasting, model blasts were conducted, and the relationships among the specific charge, fragment size, and overburden depth in the model blasts were investigated. The determined specific charge from the model blasts was then modified by considering the overburden depth and used to precondition the boulders for practical TBM tunnelling. The results indicate the following: (1) model blasts were effective in determining the correct specific charge and predicting boulder fragment sizes resulting from blasting; (2) the boulders met in practical TBM tunnelling were successfully preconditioned by using the determined specific charge; (3) the determined specific charge was 3.26 kg/m3, corresponding to an average fragment size 4.5 cm with an overburden of zero and increased with increasing overburden; (4) fragment sizes were dependent on both the specific charge and overburden depth. Our conclusions can be used to accurately determine the specific charge instead of empirical formulas.

In the context of climate change, the frequency and intensity of extreme weather events are increasing, environmental pollution and global warming are exacerbated by anthropogenic activities, and plants will experience a more complex and variable environment of stress combinations. Research on plant responses to stress combinations is crucial for the development and utilization of climate-adaptive plants. Recently, the concept of stress combinations has been expanded from simple to multifactorial stress combinations (MFSCs). Researchers have realized the complexity and necessity of stress combination research and have extensively employed composite gradient methods, multi-omics techniques, and interdisciplinary approaches to integrate laboratory and field experiments. Researchers have studied the response mechanisms of plant reactive oxygen species (ROS), phytohormones, transcription factors (TFs), and other response mechanisms under stress combinations and reached some generalized conclusions. In this article, we focus on the research progress and methodological dynamics of plant responses to stress combinations and propose key scientific questions that are crucial to address, in the context of plant responses to stress assemblages, conserving biodiversity, and ensuring food security. We can enhance the search for universal pathways, identify targets for stress combinations, explore adaptive genetic responses, and leverage high-technology research. This is in pursuit of cultivating plants with greater tolerance to stress combinations and enabling their adaptation to and mitigation of the impacts of climate change.

To investigate energy dissipation and particle size distribution of rock under dynamic loads, a series of dynamic compression tests of granite specimens were conducted using a conventional split-Hopkinson pressure bar (SHPB) device with a high-speed camera. The experimental results show that the dissipated energy increases linearly with an increasing incident energy, following two different inclined paths connected by a critical incident energy, and the linear energy dissipation law in the dynamic compression test has been confirmed. This critical incident energy was found to be 0.29–0.33 MJ/m3. As the incident energy was smaller than the critical incident energy, the rock specimens remained unruptured after the impact. When the incident energy was greater than the critical incident energy, the rock specimens were ruptured or fragmented after the impact. In addition, the experimental results indicate that the dissipated energy and energy consumption ratio of a rock specimen, either unruptured or fragmented, increase with an increasing strain rate. Furthermore, it was found that fragment sizes at each mesh decrease with an increasing incident energy; that is, fragmentation becomes finer as incident energy increases.

Reduction of energy consumption in comminution is of significant importance in mining industry. To reduce such energy consumption the energy efficiency in an individual operation such as blasting must be increased. By using both new investigations and previous experimental results, this paper demonstrates that (1) kinetic energy carried by moving fragments in rock fracture is notable and it increases with an increasing loading rate; (2) this kinetic energy can be well used in secondary fragmentation in crushing and blasting. Accordingly, part of the muck pile from previous blast should be left in front of new (bench) face in either open pit or underground blasting. If so, when new blast occurs, the fragments from the new blast will collide with the muck pile left from the previous blast, and the kinetic energy carried by the moving fragments will be partly used in their secondary fragmentation. Keywords: Kinetic energy, Rock fragmentation, Open pit blasting, Sublevel caving mining, Energy efficiency