The Establishment of Ore-Controlling Fracture System of Baoginshan Gold Mine Based on Fracture-Tectonic Analysis

The Baoginshan quartz vein type gold mine in the Baimashan-Longshan-Ziyunshan gold belt is the object of study, and the nature of the fracture structure and its ore-controlling effect are studied through surface and pit investigation, and the nature of the ore-controlling structure system and combination pattern of the Baoginshan gold mine is established. The F7 and F9 fractures in the near-east-west (EW) direction are the main fractures, which tend to the north and control the spreading of the ore zone; the northwest (NW) direction secondary tension fracture, with a dominant yield of 221°∠63°, is a T-type fracture in the Riedel shear mode and is the ore-holding structure of the vein-like ore body; the northeast-east (NEE) direction secondary shear fracture, with a dominant yield of 343°∠53°, is a P-type fracture and the combination of the two controls the specific positioning of the ore body. The characteristics and nature of the fracture structures in the whole ore zone, as well as their combination patterns, indicate that the overall ore-controlling fracture system of Baoginshan is a right-going tensional shear fracture zone composed of NW-oriented (T-type) and NEE-oriented (P-type) secondary fractures with F7 and F9 fractures as boundary fractures. The directions of the principal stresses are σ1≈158°∠40°, σ2≈288°∠38°, and σ3≈42°∠28°, respectively. In the next step of the prospecting process, based on increasing the spacing of prospecting pits (to 40m), in-pit drilling is deployed in the upper and lower discs of the NEE secondary fracture along with the tendency and strike for literacy, which can significantly improve the efficiency and effectiveness of prospecting and greatly reduce the cost of prospecting.

Characteristics of Stratum Structure and Fracture Evolution in Stratified Mining of Shallow Buried High-Gas-Thick Coal Seam by Similarity Simulation

The stratified mining of super thick coal seam is a process of repeated disturbance of the top roof, especially in the lower stratification, the upper complex rock layer has a greater settlement space, resulting in great changes in the strata structure and fissure distribution. The main coal seam thickness of Rujigou Coal Mine exceeds 20 m, due to the high gas content of the coal seam, it is prone to spontaneous combustion, and the stratified mining method is adopted. When a small-size section coal pillar (less than 10 m) is used, the complex rock structure evolution and fissure development characteristics during the stratified mining of shallow buried thick coal seam will directly affect the movement of gas transportation between the working face and the goaf and will directly affect the safety of the working face. Taking Rujigou coal mine as engineering background, this paper analyzes the breaking structure, fracture development, and evolution law of overlying strata in different layers and different sections of coal seam when the buried depth is shallow, and the extra-thick coal seam is stratified mining. The results show that in the process of stratified mining, the overlying strata break, in addition to the whole trapezoidal failure structure, will also form a local F type fracture structure, and with the stratified downward mining, the F type fracture structure will continue to move up and disappear until it is compacted. The “V” type and “U” type subsidence characteristics of different strata overburden are presented after mining in stratified working face of extra-thick coal seam, and the subsidence amount is approximately symmetrical distribution along the middle line of goaf. In the mining process of the lower part of the layer, the end broken rock block is easy to slip along the hinge point by the hinged rock beam structure, and the sliding instability occurs. In the process of stratified mining of ultrathick coal seam, the main fissure of overburden is mainly longitudinal fissure, and it is very easy to form through with the upper layer and will finally connect with the surface under the condition of shallow buried depth. The inclined cracks connected with the adjacent goaf are formed above the coal pillar of the section, which becomes the passage of gas migration in the goaf. The research conclusion shows that for the stratified mining of high gas thick coal seam, special attention should be paid to the treatment of the gas on the stratified working face. In addition to the conventional gas treatment measures such as coal seam prepumping, the buried pipe pumping in the mining area can also be adopted, which can effectively reduce the gas concentration of the working surface.

Predictors of acute compartment syndrome of the lower leg in adults following tibial plateau fractures

Background Acute compartment syndrome (ACS) is an underestimated complication following tibial plateau fractures. Understanding predictors of ACS in the lower leg after a fracture of the tibial plateau may guide earlier diagnosis and promptly decompressed by surgical fasciotomy. To date, however, there are few large-scale sample literatures to investigate the predictors of it. The purpose of our study was to evaluate the prevalence rate of ACS associated with tibial plateau fractures and identified any such predictors with the development of ACS. Materials and methods From January 2015 to January 2020, a total of 1119 consecutive patients (1119 fractures) including 703 males and 416 females with an average age of 40.7 years (18 to 80 years) in tibial plateau fractures who presented to a university-affiliated hospital with level-I trauma center were included. The presence of ACS and associated predictors were collected from patients’ electronic medical records. Associated predictors included gender, age, fracture pattern (open or closed), mechanisms of injury, fracture classification, and underlying disease. Univariate and multivariate logistical regression analyses were performed to identify the predictors of the development of ACS following tibial plateau fractures. Results Of the 1119 fractures of the tibial plateau, 35 (3.1%) developed an acute compartment syndrome. On multivariate analysis, only younger patient age (odds ratio (OR) 2.57; 95% confidence interval (CI), 1.26 to 6.31; P = 0.003), and Schatzker VI type fracture (OR 5.78; 95% confidence interval (CI), 1.78 to 54.34; P = 0.021) were significantly associated with the development of ACS. Other variables did not reach statistical significance. Conclusion Younger patient age and Schatzker VI type fracture were predictors of ACS of the lower leg in adults following tibial plateau fractures. Further studies in the prospective study are still needed to identify the potential risk factors associated with ACS in tibial plateau fractures.

Investigation into the Effect of RFSSW Parameters on Tensile Shear Fracture Load of 7075-T6 Alclad Aluminium Alloy Joints

The aim of the investigations was to determine the effect of parameters of refill friction stir spot welding (RFSSW) on the fracture load and failure mechanisms of the resulting joint. RFSSW joints were made in 7075-T6 Alclad aluminium alloy sheets using different welding parameters. The load capacity of joints was determined under tensile/shear loadings. Finite element-based numerical simulations of the joint-loading process were carried out, taking into account the variability of elasto-plastic properties of weld material through the joint cross-section. The influence of welding parameters on selected phenomena occurring during the destruction of the joint is presented. The considerations were supported by a fractographic analysis based on SEM images of fractures. It was found that there is a certain optimal amount of heat generated, which is necessary to produce the correct joint in terms of its load capacity. This value should not be exceeded, because it leads to weakening of the base material and thus to a reduction in the strength of the joint. Samples subjected to uniaxial tensile shear load showed three types of failure mode (tensile fracture, shear fracture, plug type fracture) depending on the tool rotational speed and duration of welding. Prediction of the fracture mode using FE-based numerical modelling was consistent with the experimental results. The samples that were damaged due to the tensile fracture of the lower sheet revealed a load capacity (LC) of 5.76 KN. The average value of LC for the shear fracture failure mechanism was 5.24 kN. The average value of the LC for plug-type fracture mode was 5.02 kN. It was found that there is an optimal amount of heat generated, which is necessary to produce the correct joint in terms of its LC. Excessive overheating of the joint leads to a weakening of the base metal and thus a reduction in the strength of the joint. Measurements of residual stresses along the axis specimens showed the presence of stresses with a certain constant value for the welded area on the side of the 1.6 mm thick plate.

A study of grain refinement of AZ91E and Mg-9 wt.% AI alloys using zinc oxide

Grain refinement is a proven method to improve mechanical properties of Mg alloys. In this research, the influence of ZnO on the microstructure of selected magnesium alloys was investigated. For graphite mold casting with an addition of 0.75 wt. % ZnO, the grain size of the AZ91E alloy decreased from 217 μm to 108 μm. For the binary alloy (Mg-9 wt.% Al), the grain size reduced from 288 μm to 93 μm with an addition of 3 wt.% ZnO. No significant fading of ZnO grain refiner was observed for both the alloys. In permanent mold casting process, with an addition of 0.5 wt.% ZnO, the grain size of the AZ91E alloy decreased from 133μm to 79 μm with significant improvements in mechanical properties. Cleavage type fracture was dominant in the base alloy while alloys refined with 0.5 wt.% ZnO showed more quasi-cleavage type fracture.

A study of grain refinement of AZ91E and Mg-9 wt.% AI alloys using zinc oxide

Grain refinement is a proven method to improve mechanical properties of Mg alloys. In this research, the influence of ZnO on the microstructure of selected magnesium alloys was investigated. For graphite mold casting with an addition of 0.75 wt. % ZnO, the grain size of the AZ91E alloy decreased from 217 μm to 108 μm. For the binary alloy (Mg-9 wt.% Al), the grain size reduced from 288 μm to 93 μm with an addition of 3 wt.% ZnO. No significant fading of ZnO grain refiner was observed for both the alloys. In permanent mold casting process, with an addition of 0.5 wt.% ZnO, the grain size of the AZ91E alloy decreased from 133μm to 79 μm with significant improvements in mechanical properties. Cleavage type fracture was dominant in the base alloy while alloys refined with 0.5 wt.% ZnO showed more quasi-cleavage type fracture.

A Study on the Mechanism of Dynamic Pressure during the Combinatorial Key Strata Rock Column Instability in Shallow Multi-coal Seams

In order to study the pressure changes and support failure in mining face under concentrated coal pillar in shallow coal seam, the concentrated coal pillar in 30105 working face of Nan Liang Coal Mine was selected as the research object. In this study, the mechanism of dynamic mine pressure in mining face under concentrated coal pillar was investigated through multiple simulation experiments, numerical simulations, and theoretical analysis. The results of similar simulation experiment indicate that the dynamic mine pressure occurred at 25 m under the concentrated coal pillar and 7 m beyond the coal pillar. The strata roof was observed with sliding down, resulting in collapse and severe fractures commonly seen in rock column. The overlying strata caused the overall subsidence and collapse synchronously, resulting in the sudden increase of the resistance of the support in the working face, and the dynamic load coefficients reach 3.4 and 3.5. The theoretical analysis indicates that the two hard strata in the overlying strata of 3−1 coal meet the theoretical criterion of the combined key strata with the concentrated coal pillar of 2−2 coal in the weak interlayer of the combined key strata. The combined key strata bear the load of the whole overlying strata. The sliding instability featured with the rock column-type fracture located in the combined key strata is considered as the primary trigger of the abnormal resistance of the support and the dynamic mine pressure in the mining face under the concentrated coal pillar. The dynamic pressure model of “combination key strata—immediate roof-support” was established, along with the dynamic load coefficient calculation related to the rock column-type fracture and instability. The characteristics of dynamic load coefficient of the rock column-type fracture and instability under different overlying rock structure conditions were analyzed, providing references and insights into mining under similar geographic conditions.

LATERAL HUMERAL CONDYLAR FRACTURE IN A PAEDIATRIC MONTEGGIA TYPE III EQUIVALENT

Monteggia fracture dislocations can be classic or equivalents. Equivalents, also known as Monteggia like lesions, are very rare especially type III and IV, which have been added to the literature after Luis Bado presented the original classification system of Monteggia fracture dislocations. Type III equivalent is classically defined as a proximal ulna fracture associated with a fracture of the lateral condyle of the humerus. In the literature only seven such cases have been reported so far. Here we present two such cases where one eight-year-old boy had a complex type of injury with a shear type fracture of the lateral humeral condyle and other a seven-year-old boy who had a plastic deformity of the ulna with an avulsion type fracture of the lateral humeral condyle. We also try to describe a novel mechanism of injury, known as, “Barzulla circle”, for the classical as well as equivalent type III Monteggia fracture dislocations.