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At present, non-pillar entry protection in longwall mining is mainly achieved through either the gob-side entry retaining (GER) procedure or the gob-side entry driving (GED) procedure. The GER procedure leads to difficulties in maintaining the roadway in mining both the previous and current panels. A narrow coal pillar about 5–7 m must be left in the GED procedure; therefore, it causes permanent loss of some coal. The gob-side pre-backfill driving (GPD) procedure effectively removes the wasting of coal resources that exists in the GED procedure and finds an alternative way to handle the roadway maintenance problem that exists in the GER procedure. The FLAC3D software was used to numerically investigate the stress and deformation distributions and failure of the rock mass surrounding the previous and current panel roadways during each stage of the GPD procedure which requires "twice excavation and mining". The results show that the stress distribution is slightly asymmetric around the previous panel roadway after the “primary excavation”. The stronger and stiffer backfill compared to the coal turned out to be the main bearing body of the previous panel roadway during the "primary mining". The highest vertical stresses of 32.6 and 23.1 MPa, compared to the in-situ stress of 10.5 MPa, appeared in the backfill wall and coal seam, respectively. After the "primary mining", the peak vertical stress under the coal seam at the floor level was slightly higher (18.1 MPa) than that under the backfill (17.8 MPa). After the "secondary excavation", the peak vertical stress under the coal seam at the floor level was slightly lower (18.7 MPa) than that under the backfill (19.8 MPa); the maximum floor heave and maximum roof sag of the current panel roadway were 252.9 and 322.1 mm, respectively. During the "secondary mining", the stress distribution in the rock mass surrounding the current panel roadway was mainly affected by the superposition of the front abutment pressure from the current panel and the side abutment pressure from the previous panel. The floor heave of the current panel roadway reached a maximum of 321.8 mm at 5 m ahead of the working face; the roof sag increased to 828.4 mm at the working face. The peak abutment pressure appeared alternately in the backfill and the coal seam during the whole procedure of "twice excavation and mining" of the GPD procedure. The backfill provided strong bearing capacity during all stages of the GPD procedure and exhibited reliable support for the roadway. The results provide scientific insight for engineering practice of the GPD procedure.

Understanding the hydraulic fracture (HF) re-orientation mechanism from artificial weaknesses is critical to screen-out prevention in the petroleum industry and caveability management in the mining industry. An improved discrete element method is proposed and incorporated in the Universal Distinct Element Code (UDEC) to simulate hydraulic fracturing in heterogeneous rocks, and its reliability is validated against previous laboratory experiments. The effects of rock heterogeneity and rock strength on HF re-orientation are unveiled to fill the research gaps in the existing knowledge. The results show that the proposed UDEC T-W (Trigon-Weibull distribution) model can well simulate HF propagation in rock samples of different homogeneity degrees and yields more realistic simulation results compared with the classic extended finite element method (XFEM). The HF re-orientation process depends on the combined effect of all the influencing factors. HFs tend to be directed by perforations if hydraulic fracturing is performed in relatively heterogeneous rocks, while the differential stress is more likely to dictate the HF propagation paths if rocks become relatively homogeneous. We also find that higher rock strength weakens the impact of the differential stress and favours the control of perforations over HF propagation. Finally, recommendations are provided for effective utilization of hydraulic fracturing at the mine site.

Soybean seeds contain high levels of oil and protein, providing 57 and 69% of a person's dietary requirements, respectively. Although many quantitative trait loci for the 100-seed weight (100SW), protein content (PRC), and oil content (OIC) have been reported, their genetic controls in soybeans remain unclear. The QTL–allele constitution of three traits in the Sichuan and Chongqing eco-regions population (SCLBP) was studied using a representative sample composed of 228 accessions. These were tested in four environments and analyzed using 135 simple sequence repeats (SSR) and 107,081 valid single nucleotide polymorphism linkage (SNP) markers. The range of 100SW, PRC, and OIC in SCLBP accessions were 4.82–33.35, 36.47–49.75%, and 14.68–21.77%, respectively. The heritability (h2) and genetic coefficient of variation (GCV) of the three traits were high. As a result, 26, 33, and 31 QTLs were found using SSR for 100SW, PRC, and OIC, respectively. The allele of Sat_260 for 100SW was detected in the four environments. In addition, 28, 198, and 250 loci for 100SW, PRC, and OIC, respectively, were found using SNP and mixed linear model (MLM). Further SNP haplotype analysis revealed that 13, 35, and 60 blocks were found for 100SW, RPC, and OIC, respectively. The block of Gm11_9895764-9,917,646 for 100SW was simultaneously detected in the four environments. Among these QTLs, 1, 5, and 7 for 100SW, PRC and OIC were found using two methods of SSR and SNP at the same time. A majority of these QTLs overlapped with the previously reported loci. However, 9, 11, and 9 loci for 100SW, PRC, and OIC using SSR; and 3, 5, and 8 for 100SW, PRC, and OIC hadn’t been reported using SNP. Moreover, the genes of Glyma.11g130800, Glyma.13g217000, and Glyma.08g122600 were considered the most likely genes controlling 100SW, PRC, and OIC, respectively. These findings provide evidence for mixed major plus polygenes inheritance for the three traits and an extended understanding of their genetic architecture for the molecular dissection and breeding of soybeans.

During duration spaceflight, or after their return to earth, astronauts have often suffered from gait instability and cerebellar ataxia. Here, we use a mouse model of hindlimb unloading (HU) to explore a mechanism of how reduced hindlimb burden may contribute to motor deficits. The results showed that these mice which have experienced HU for 2 weeks exhibit a rapid accumulation of formaldehyde in the gastrocnemius muscle and fastigial nucleus of cerebellum. The activation of semicarbazide-sensitive amine oxidase and sarcosine dehydrogenase induced by HU-stress contributed to formaldehyde generation and loss of the abilities to maintain balance and coordinate motor activities. Further, knockout of formaldehyde dehydrogenase (FDH-/-) in mice caused formaldehyde accumulation in the muscle and cerebellum that was associated with motor deficits. Remarkably, formaldehyde injection into the gastrocnemius muscle led to gait instability; especially, microinfusion of formaldehyde into the fastigial nucleus directly induced the same symptoms as HU-induced acute ataxia. Hence, excessive formaldehyde damages motor functions of the muscle and cerebellum., Dandan Yao et al. demonstrated that accumulation of formaldehyde in the cerebellum and skeletal muscle contributed toward motor deficits in a mouse model of hindlimb unloading. Their results collectively suggest that scavenging formaldehyde may be a useful treatment to limit motor dysfunction following limb offloading conditions.

Mechanical responses of rocks to combined compression and shear have attracted increasing attention but still lack comprehensive understanding. Sixty-eight laboratory tests are conducted on basalt and granite specimens sourced from different origins to generalize the effects of specimen inclination on the mechanical properties of igneous rocks. A novel regression model is established to predict peak strength and elastic moduli of igneous specimens at various inclination angles. The model mechanically considers both the individual effect and the combined effect of independent factors. It is found that specimen inclination has nearly the same effects on the failure patterns, strength, and elastic moduli of all the experimented igneous rocks regardless of origins. Igneous rocks tend to fail in shear under combined compression and shear loading. Both their strength and elastic moduli decline approximately linearly as specimen inclination increases. The reductions of both the strength and the elastic modulus as specimen inclination increases are closely associated with the UCS (θ = 0°) and the Young’s modulus (θ = 0°), respectively. The ratio of the peak strength to the elastic modulus is an inherent property of the igneous specimen, independent of the specimen strength and inclination.

The mechanical characteristics of brittle materials submitted to combined compression and shear loading (CCSL) have received considerable attention recently. Both dynamic and quasi-static CCSL tests have been experimented to simulate the realistic working conditions encountered by different materials. Nevertheless, how the external shear loading affects the microcrack fracturing of rock still excludes explanation. In this paper, a self-developed loading device, instrumented with acoustic emission monitoring, is used to uncover the effect of sample inclination on the microcrack fracturing thresholds of granite samples sourced from two different places. Our laboratory results show that the microcrack damage thresholds (σcd) of the granite samples drop almost linearly with higher sample inclination whereas the microcrack initiation thresholds (σci) only decline when the inclination angle is elevated to a certain magnitude. The changes of the σci/σc ratios (the σci to peak strength ratios) and the σcd/σc ratios against the sample inclination are rock origin dependent. Multiple regression analysis is conducted to unveil the correlation among microcrack fracturing thresholds, peak strength and sample inclination. Both σci and σcd are more sensitive to the combined influence of the peak strength and the inclination angle compared with the individual effect of these two factors. Finally, empirical formulae are proposed to provide reliable predictions of σci and σcd at different sample inclination based on the peak strength acquired from the CCSL tests.

Size and shape of soybean seeds are closely related to seed yield and market value. Annual wild soybeans have the potential to improve cultivated soybeans, but their inferior seed characteristics should be excluded. To detect quantitative trait loci (QTLs)/segments of seed size and shape traits in annual wild soybean, its chromosome segment substitution lines (CSSLs) derived from NN1138-2 (recurrent parent, Glycine max) and N24852 (donor parent, Glycine soja) and then modified 2 iterations (coded SojaCSSLP3) were improved further to contain more lines (diagonal segments) and less heterozygous and missing portions. The new population (SojaCSSLP4) composed of 195 CSSLs was evaluated under four environments, and 11, 13, 7, 15 and 14 QTLs/segments were detected for seed length (SL), seed width (SW), seed roundness (SR), seed perimeter (SP) and seed cross section area (SA), respectively, with all 60 wild allele effects negative. Among them, 16 QTLs/segments were shared by 2–5 traits, respectively, but 0–3 segments for each of the 5 traits were independent. The non-shared Satt274 and shared Satt305, Satt540 and Satt239 were major segments, along with other segments composed of two different but related sets of genetic systems for SR and the other 4 traits, respectively. Compared with the literature, 7 SL, 5 SW and 2 SR QTLs/segments were also detected in cultivated soybeans; allele distinction took place between cultivated and wild soybeans, and also among cultivated parents. The present mapping is understood as macro-segment mapping, the segments may be further dissected into smaller segments as well as corresponding QTLs/genes.

The cave mining method was traditionally applied to massive low-grade, weak orebodies at shallow depths (less than 500 m) that favour cave propagation under gravity. Currently, this method is being applied to stronger orebodies and is taking place at depths of up to 2000 m below the surface. To ensure continuous cave propagation, preconditioning of the orebody is essential in this latter caving environment to improve rock mass caveability and to decrease fragmentation sizes. Hydraulic fracturing was initiated in the oil industry and is now being used in the cave mining industry as a preconditioning method and for stalled caves reactivation. A limitation of conventional hydraulic fracturing in the cave mining industry is that the hydraulic fracture orientation is uncontrollable and is dictated by the minimum in situ stress orientation. The preconditioning effectiveness of orientation-uncontrollable hydraulic fractures is limited in some geotechnical conditions, and the concept of creating orientation-controllable hydraulic fractures, here termed prescribed hydraulic fractures, is proposed to fill this gap. In this paper, the feasibility of the proposed approaches to creating prescribed hydraulic fractures is presented based on previous studies and numerical modelling. The numerical modelling code reliability in simulating the hydraulic fracture propagation and reorientation process was validated by comparing with laboratory results in the reported literature. In addition, the sensitivity of the prescribed hydraulic fracturing to the in situ stress condition and rock mass properties is examined.

Hydraulic fracturing has been used in cave mining for preconditioning the orebody following its successful application in the oil and gas industries. In this paper, the state of the art of hydraulic fracturing as a preconditioning method in cave mining is presented. Procedures are provided on how to implement prescribed hydraulic fracturing by which effective preconditioning can be realized in any in situ stress condition. Preconditioning is effective in cave mining when an additional fracture set is introduced into the rock mass. Previous studies on cave mining hydraulic fracturing focused on field applications, hydraulic fracture growth measurement and the interaction between hydraulic fractures and natural fractures. The review in this paper reveals that the orientation of the current cave mining hydraulic fractures is dictated by and is perpendicular to the minimum in situ stress orientation. In some geotechnical conditions, these orientation-uncontrollable hydraulic fractures have limited preconditioning efficiency because they do not necessarily result in reduced fragmentation sizes and a blocky orebody through the introduction of an additional fracture set. This implies that if the minimum in situ stress orientation is vertical and favors the creation of horizontal hydraulic fractures, in a rock mass that is already dominated by horizontal joints, no additional fracture set is added to that rock mass to increase its blockiness to enable it cave. Therefore, two approaches that have the potential to create orientation-controllable hydraulic fractures in cave mining with the potential to introduce additional fracture set as desired are proposed to fill this gap. These approaches take advantage of directional hydraulic fracturing and the stress shadow effect, which can re-orientate the hydraulic fracture propagation trajectory against its theoretical predicted direction. Proppants are suggested to be introduced into the cave mining industry to enhance the induced stress shadow effect if prescribed hydraulic fractures are required. The feasibility of the proposed approaches will be investigated in future studies.

Chromosome segment substitution line (CSSL) population is potential in precisely detecting and pyramiding genes/QTL/segments due to the genetic background noise removed. To exploit and utilize the favorable wild alleles, a CSSL population with 151 lines (SojaCSSLP1) was generated using a wild soybean (Glycine soja Sieb. et Zucc.) N24852 as donor parent and the elite cultivar NN1138-2 as its genetic background. An improved CSSL construction strategy was used, i.e. continuous backcross after initial crossing followed with alternation of backcross and selfing combined with marker-assisted selection based on pedigree DNA pools and phenotypic differences among pedigrees. The SojaCSSLP1 with an average recovery ratio of 95.7 % of the NN1138-2 genome could cover the entire genome of wild soybean. Four wild alleles/segments for each of the two wild characteristics, longer plant height (PH) and more number of nodes on main stem (NN), in a total of six segments, were detected with additive effects all positive. Among them, Satt243 on Chr.10 and Sat_286 on Chr.19 associated with both PH and NN while Satt338 and SOYGPATR on Chr.4 and Satt314 neighboring with Satt192 on Chr.12 had the former and latter on each chromosome associated with PH and NN, respectively. That could explain the high positive correlation between the two traits (r = 0.88). Compared with those in the literature, three QTL/segments for PH and one for NN were detected also among cultivated soybeans, indicating allele differentiation happened not only between wild and cultivated but also among cultivated soybeans. Therefore these QTL/segments might be the key ones to explain the domestication and evolution of soybean. In addition, SojaCSSLP1 should be also potential in studies for multiple wild traits due to its broad variation.