煤炭科学研究总院有限公司

Anchorage support is extensively utilized in the stability control of underground structures.The performance of such support varies with anchorage parameters,particularly influenced by the relative position between the anchorage section and the joints in the surrounding rock,which significantly affects the shear resistance of the bolts.To investigate the impact of anchorage parameters on the shear mechanical behavior of bolted joints,a series of shear tests were conducted with varying anchorage lengths and thicknesses.The results indicate that,for a given anchorage thickness,increasing the anchorage length enhances the average shear peak strength and the rod breaking strength by 3.15%and 2.56%,respectively,while simultaneously reducing the average deformation range and the breaking displacement of the bolts by 18.41%and 16.48%,respectively.For a constant anchorage length,an increase in anchorage thickness improves the average shear peak strength and breaking strength by 1.93%and 1.64%,respectively.Post-failure,the deformed bolts exhibit an"S"-shaped profile.As the anchorage length increases,the deformation becomes more symmetric,the normal displacement at peak failure decreases,the axial force reduces,and the shear force provided by the bolts increases.In the pre-peak stage,the ring-down count and energy account for 61.7%and 58.5%of the total,respectively,while the b-value reaches its lowest point at the shear peak.During the post-peak deformation stage,the b-value continuously rises,peaking at the breaking point.Through Gaussian Mixture Model(GMM)statistics of crack types,it is concluded that the shear failure of the bolted joint predominantly occurs in shear,with an average of 86.05%attributed to acoustic emission shear failure and only 13.95%to tensile failure.

During deep coal mining,interlayer rock strata subjected to high static stress and low-frequency dynamic load are prone to fracture and instability,often leading to dynamic disasters.To investigate the dynamic response of rock fracture,deformation,and mechanical behavior under low-frequency disturbances,uniaxial compression tests were conducted on perforated sandstone specimens at different loading rates.This study explores the crack evolution,fracture ejection patterns,and dynamic strain behavior of sandstone under disturbance.The results reveal the following key findings:(1)The mechanical properties of sandstone are significantly influenced by the loading rate,with peak strength increasing nonlinearly as the loading rate rises.When the loading rate increases fivefold,the average peak strengths of the single-hole,double-hole,and triple-hole specimens increase by 9.67％,14.64％,and 9.44％,respectively.However,as the number of perforations increases,the overall load-bearing capacity of sandstone decreases,and the average peak strengths are reduced by 12.58％,12.15％,and 13.23％,respectively.(2)The acoustic emission(AE)characteristics and stress-time evolution curves of sandstone exhibit distinct inflection points.AE activity is relatively weak during the crack initiation stage,but AE events increase sharply before failure,accompanied by an exponential rise in AE energy.This phenomenon can serve as an early warning indicator of dynamic failure in high-stress sandstone under low-frequency disturbances.(3)Based on the failure modes and the extent of surface spalling and block ejection,sandstone failure can be classified into three types.The mean σc/σz values for type Ⅰ,Ⅱ,and Ⅲ specimens are 0.959,0.765,and 0.687,respectively,indicating significant differences in mechanical properties among different failure modes.(4)The strain distribution in the rock specimens is closely related to the number of perforations.As the number of perforations increases,pronounced stress shielding zones and horizontal tensile strain zones develop between the holes during loading,providing the main pathways for crack propagation.

Coal is the cornerstone of China's energy security.There are many types and wide distributions of coal associated resources,with abundant reserves and high utilization value.Promoting the integrated green development of coal and associated resources is an inevitable requirement for improving the efficiency of resource development and utilization,accelerating the green transformation of development mode,and ensuring national resource security in the new era.This article clarifies the combination types,distribution and typical resources of coal and associated resources.The technological maturity of coal and associated resource development has been analyzed.Four typical development models of coal and associated resource technology integration,development subject integration,management integration,and industrial chain integration have been analyzed.The development benefits in terms of economy,security,and ecology have been evaluated and the key problems currently existing have been summarized.On this basis,a strategic blueprint for the integrated green development of coal and associated resources in China has been depicted,the"three-step"strategic goal has been proposed,the integrated green development technology system covering integrated digital survey and design technology,safe and efficient collaborative development technology,and intelligent green low-carbon technology has been constructed,and the strategic path framework of"four advances,one exploration"has been constructed.Finally,policy recommendations have been put forward to promote the integrated green development of coal and associated resources,including improving the mining rights management system,forming a joint exploration and mining mechanism,increasing investment in scientific and technological innovation,and establishing a coordinated exploration and development incentive mechanism.

ObjectiveLong-distance oil and gas transmission pipelines are important energy infrastructures. Currently, there are deficiencies in the automatic tracking accuracy and adaptability of external welding machines during pipeline construction. Operators often need to manually adjust external welding equipment (welding torch) to ensure the quality of the joints. Improving the intelligence of the welding process is an effective way to improve the efficiency and joint qualification rate during the on-site laying of long oil and gas pipelines. This study proposes a detection and control algorithm for the welding torch position and posture, applicable to all position welding of workpieces with arbitrary spatial postures.MethodsThis study is the first to design a multisource sensor that combines laser-structured light vision sensing with dual-axis tilt sensing. This multisource sensor combines the advantages of both types of sensing, enabling it to detect the relative position information of the welding torch, as well as the posture information of the welding torch and workpiece. Using this multisource sensor, the algorithm performs integrated calculations of the welding groove size parameters and relative position and posture parameters of the welding torch under any workpiece posture through local groove surface reconstruction. This method fully uses laser line data from images to ensure stable, applicable, and accurate parameter calculations. Through coordinate transformation, the spatial posture (αw and βw) of the local workpiece can be obtained. These integrated feature parameters provide the basis for controlling the welding torch's spatial position and posture in any pipeline space all-position welding. Next, a pipeline intelligent welding system with five degrees of freedom based on multisource sensing is constructed. The system, combined with the designed algorithm, achieves real-time control of the welding torch position and posture (e, H, α, and β), meeting welding process requirements and enabling high-quality weld formation control during arc welding.ResultsThe experimental results show that the attitude angle feedback control error of the welding torch did not exceed 0.8°, the lateral position tracking deviation was within 0.25 mm, and the height tracking deviation did not exceed 0.63 mm during the pipeline all-position welding process. Compared to existing welding seam detection and tracking systems based on structured light-vision sensing, the proposed algorithm offers superior accuracy and stability. It detects not only the position deviation of the welding torch but also the posture of the welding joint on any unstructured surface with an unknown spatial posture.ConclusionsThe proposed algorithm for detecting and controlling the position and posture of the welding torch can be used to achieve accurate control during pipeline space all-position welding. This advancement significantly improves the intelligence level of pipeline external welding equipment and provides technical support for controlling the position and posture control of the welding torch when welding unknown posture-curved workpieces.

In view of the problems of strong mine pressure such as rapid shrinkage of hydraulic support column and easy support crushing in working face under the fully mechanized caving face with large mining height in multi-layer thick and hard roof of extra-thick coal seam in Yushen mining area,the support working resistance and roof subsidence during the mining period of the working face are systematically monitored by using column pressure sensor and displacement sensor,and the macroscopic characteristics of mine pressure behavior and the linkage between near and far field overburden movement and mine pressure are analyzed.The characteristics of mine pressure in fully mechanized caving face with large mining height and multi-layer thick and hard roof were clarified,the spatial form of multi-layer thick and hard roof break-ing and the evolution law of overburden structure were obtained,and the mechanism of mine pressure was expounded.The mechanical model of overburden structure in different layers of low,medium and high layers was established considering the bending deformation in front of the coal wall and the stress correlation between the layers of multi-layer thick and hard roof.The criterion of rock failure instability and the critical support strength of the support in different layers were given.The results show that the mining of fully mechanized top coal caving face with multi-layer thick and hard roof and large mining height not only has the characteristics of"obvious regional pressure,rapid increase of pressure resistance,large and small periodic pressure,periodic strong dynamic load pressure",but also presents the new characteristics of multiple continuous or short-distance intermittent large periodic pressure during strong dynamic load pressure.During the period of strong dynamic load,the degree of continuous large-period rock pressure shows a trend of increasing first and then de-creasing,the periodic strong dynamic load pressure of the working face is irregular,with 4 to 10 small cycles,an interval of 120.9-241.9 m and an average interval of 161 m.During the period of strong dynamic load pressure,the mine pressure ap-pears abnormally strong.The high-level rock stratum is located more than 70 m above the coal seam.After the thick and hard rock stratum in the middle is broken,the effective contact and support force of the high-level"hinged beam"is re-duced,resulting in the failure and instability of the high-level hinged beam,which in turn leads to the strong dynamic load pressure phenomenon of multiple continuous or short-distance intermittent large-cycle pressure in the working face.The reasonable support strength of the support is 1.897 MPa when the middle"non-articulated beam"structure is broken and unstable.The reasonable support strength of the support corresponding to the rotary deformation instability of the"hinged beam"is 2.470 MPa,and the reasonable support strength of the support corresponding to the sliding instability is 3.180 MPa.The existing high-strength support is difficult to effectively control the strong mine pressure of the roof.It is neces-sary to adopt the means of roof weakening to control the surrounding rock of the stope.The research results have import-ant guiding significance for the surrounding rock control of multi-layer thick and hard roof mining in extra thick coal seam.