In order to solve the problem that the surrounding rock control of the pre-excavation double-retracement channel is difficult and a large number of coal pillars cannot be recovered. Taking chuancaogeban coal mine as the engineering background, the mechanical model in the process of gradual connection between coal mining face and main withdrawal channel is constructed, and the response characteristics of surrounding rock in withdrawal channel are simulated and verified by FLAC3D numerical calculation model. The instability mechanism of this kind of roadway is revealed, and a comprehensive stability control technology of surrounding rock and the technology of recovering all coal pillars are proposed, and the field engineering verification is carried out. The results show that when the coal mining face is close to the main retracement channel, when the distance between the coal mining face and the main retracement channel is 4 m, the coal body between the coal mining face and the main retracement channel enters an unstable state. Using 8 m wide filling wall to replace the coal pillar between the main retracement channel and the auxiliary retracement channel can ensure the stability of the surrounding rock of the two retracement channels after the coal mining face passes through the main retracement channel. In addition, the retained auxiliary withdrawal channel also has the functions of auxiliary production and coal pillar recovery, and finally realizes the technology of pre-excavation double withdrawal channel without coal pillar abandonment. As the coal mining face gradually approaches the main retracement channel, the surrounding rock stress of the main retracement channel and the auxiliary retracement channel has significant dynamic development. Based on the development law of the deviatoric stress of the surrounding rock, the combined control technology of ' pre-cutting roof + high water material pillar + grouting reinforcement + single pillar + metal mesh + steel ladder belt + bolt + anchor cable ' in different regions is proposed. The field monitoring results show that during the removal of coal mining equipment, the surrounding rock deformation of the withdrawal channel is small, the surrounding rock control effect is good, and the equipment is safely and efficiently removed; during the recovery of coal pillars, the surrounding rock deformation of the retained auxiliary withdrawal channel meets the needs of production. The recoverable resources of coal seams will increase by 747,000t, and the economic benefits will increase by 117 million yuan.

Defects in the circumferential welds of long-distance natural gas pipelines are a major threat to pipeline operational safety. This paper presents the design of an in-pipe inspection robot platform for DN1016 large-diameter natural gas pipelines, featuring three short sections connected in series and an umbrella-shaped link mechanism for adaptive diameter adjustment. A quasi-static theoretical model for the drive wheel crossing the circumferential weld was established, and analytical expressions for the maximum obstacle-crossing height were derived based on both traction boundary conditions and anti-slip adhesion conditions. An obstacle-crossing simulation model was developed using ADAMS multibody dynamics software, and parametric transient dynamic analyses were conducted within a speed range of 0.12–1.2 m/s. A 1:5 scale-down proof-of-concept prototype was developed, and an acrylic simulated pipeline test rig was constructed to conduct experiments on bend passability and circumferential weld obstacle crossing. The research results indicate that the design dimensions of the robot—a single-section body of 1,450 mm and a universal joint of 183 mm—meet the geometric passability requirements for a 5D bend (R = 5,080 mm); the maximum obstacle-crossing height is approximately 8.5 mm, meeting the engineering standard of a circumferential weld reinforcement height of ≤ 6 mm within the pipe; at the recommended obstacle-crossing speed of 0.24 m/s, the peak torque of the drive wheel is 12.4 N·m, with a vertical displacement of the center of mass of only 0.25 mm and a displacement attenuation rate exceeding 95%; the scaled-down experiments validated the radial yielding capacity of the variable-diameter mechanism and the feasibility of obstacle crossing.

High-dimensional vibration features in mechanical fault diagnosis often contain substantial redundancy, while existing dimensionality-reduction and feature-selection methods may provide limited physical interpretability and noise robustness. This paper proposes a bi-level optimization feature-selection model based on Pareto optimization and cross-entropy loss. First, empirical mode decomposition (EMD) and statistical descriptors are used to construct an original feature set, which is pre-screened using a permutation test. Next, the lower-level model uses non-dominated sorting genetic algorithm II (NSGA-II) to obtain a Pareto front by maximizing feature–label dependence while minimizing inter-feature redundancy and subset size. The upper-level model then selects the subset with the lowest multilayer perceptron (MLP) validation cross-entropy loss. The framework is evaluated on the public HUST, XJTU, and CWRU fault-diagnosis datasets. Across 15 dataset-classifier configurations, the mean accuracy reaches 98.1% under noise-free conditions. Under 0 dB mixed noise, RF maintains accuracies above 94% on all three datasets. In the XJTU gearbox ablation experiment, the number of selected features is reduced by 49.8% under noise-free conditions and 60.7% at 0 dB. By integrating statistically controlled candidate-space screening, multi-objective Pareto optimization, and task-loss-driven subset selection, the framework preserves the physical semantics of the original features while producing compact, interpretable, and noise-robust subsets for high-dimensional, small-sample vibration diagnosis.

Taking the No.4 coal seam in the return air roadway in the upper formation No.1 coal mining area of a mine as the background, based on the energy dissipation theory, the energy dissipation mechanical model of arch roadway was established based on the energy balance equation and the energy analysis theory of surrounding rock loose circle, and the failure range of surrounding rock loose circle was positively correlated with the energy dissipation. Based on the Moore-Coulomb strain softening constitutive model, the energy dissipation fish program based on FLAC3D software was developed and numerical simulation was carried out, and the average energy dissipation range of the roadway in the model was determined to be 5.9 m. Combined with the field drilling imaging test, the failure range of the loose ring of the surrounding rock of the roadway was determined to be 5.9 m and 6.04 m respectively. The above content proves that the energy dissipation theory can be well applied to the analysis of the loose zone of surrounding rock.

Aiming at the problem of large deformation and instability control of narrow coal pillar in the vertical stratification section of extra-thick coal seam, the stability and control technology of the surrounding rock of narrow coal pillar in extra-thick coal seam are studied by combining theoretical analysis, numerical simulation and field test. Based on the calculation of the triaxial stress in the narrow coal pillar, the yield criterion of the plane strain of the narrow coal pillar is obtained based on the Mohr-Coulomb failure strength, the failure characteristics and the evolution law of the damage degree of the narrow coal pillar are qualitatively analyzed, and the instability mechanism and size effect of the narrow coal pillar are further analyzed. Finally, the key technologies of surrounding rock control of the narrow coal pillar are given. It is verified by numerical simulation and field test. The research results show that ① The damage degree of the middle part of the narrow coal pillar is greater than that of the two sides, and the damage degree of the middle part from the top to the bottom develops from serious to slight. With the increase of width-height ratio, the damage degree and the proportion of serious damage area in the narrow coal pillar gradually decrease. When the width-height ratio is greater than 1∶1, a large range of slight damage area begins to appear in the middle and lower part of the narrow coal pillar. When the width-height ratio is greater than 5∶3, the proportion of slight damage area exceeds 50%. When C≥3 MPa, or φ≥20°, the damage degree of the two sides of the narrow coal pillar becomes slight. ② The side of the mining roadway in the working face is a low-stress bearing area of the narrow coal pillar. Under the action of high stress in the upper part, the coal body in the large-scale low-stress bearing area moves to the roadway, resulting in a continuous large deformation of the two sides, which in turn affects the stability of the roof. The height of coal pillar is the main controlling factor for the stability of the narrow coal pillar in the middle and bottom layered sections. The increase of width-height ratio of the narrow coal pillar has little influence on the bearing strength of high strength bearing area, while the bearing strength of low strength bearing area increases obviously. Reasonable width-height ratio of the narrow coal pillar can balance the proportion of high and low strength bearing area in coal pillar. ③ The stability of surrounding rock should be considered in the design of layered narrow coal pillars when both sides of the working face are mined out, so as to ensure that the range of high-strength bearing area inside the coal pillar is greater than half of the width and height of the coal pillar. Through the joint strengthening support measures, multiple joint control areas from shallow to deep are formed in the coal pillar to jointly maintain the self-stability of the coal pillar.

Reducing the internal flow resistance of turbine blades can improve the overall efficiency of aero engines. To address the issue of the large internal flow losses in traditional horizontal exhaust slots for trailing edge cooling, structure of radially tilted trailing edge slots was proposed in previous work, and the flow resistance reduction ability of the novel scheme was investigated through numerical simulations under typical engine working conditions. Building on this, this research aimed to investigate the flow resistance of both novel and traditional schemes under ordinary pressure conditions through a combination of experimental and numerical methods. The results indicated that the tilted scheme exhibited a reduction in total pressure loss of approximately 5.7–9.1

The destruction of rock under the condition of a close submerged jet has become a hot topic of scientific research and engineering application in the past decade. With the unremitting efforts of a large number of experts and scholars around the world, gratifying progress has been made in the research of computational fluid dynamics (CFD) on the internal and external flow fields of the jet nozzle, the theoretical derivation of rock mechanics on the fracture initiation and propagation criteria of hydraulic fracturing, and the numerical simulation of jet erosion mechanism under the coupling of fluid and solid fields, however, for the rock mechanics hydraulic fracturing cutting engineering scale of non-oil drilling fracturing technology, the research on the fluid-solid coupling boundary conditions of fracturing fluid and hard dense rock under the flow state conditions of the submerged field inside and outside the borehole is not sufficient. In the calculation of the fluid-solid coupling boundary flow field under the non-submerged jet state, the control equation with Reynolds number between 2300-4000 shall be selected, while it belongs to the laminar flow state in the stage of hole sealing and pressurised fracturing. Therefore, Von-Mises equivalent plastic stress is selected in the mechanical model to calibrate the failure state of the rock-solid boundary, and the control equations of laminar flow and turbulent flow are selected to calibrate the fluid boundary. The mechanism of different stages of rock breaking by hydraulic fracturing jet can be further analysed in detail, and Comsol 6.0 multi-physical field simulation software is selected for verification. The research results will help deepen the understanding of rock breaking mechanism by jet and optimise the selection of parameters for field construction.

With the development of the times, the problem of mechanical failures in bearings has gradually become prominent. If this problem cannot be solved, it would cause significant safety hazards, so new technologies are needed to solve this problem. The research in this article was an analysis of the bearing mechanical fault safety diagnosis method based on the improved PSO (Particle Swarm optimization) algorithm, which aimed to improve the accuracy of bearing mechanical fault safety diagnosis by using the PSO algorithm. This article tested the accuracy of bearing mechanical fault diagnosis using PSO algorithm through experiments, with a maximum of 85% and a minimum of 80%. The accuracy of traditional bearing mechanical fault diagnosis was as high as 60% and as low as 50%. From this experimental data, it could be seen that the accuracy of bearing mechanical fault diagnosis was significantly improved using the PSO algorithm, indicating a good fit between the PSO algorithm and bearing mechanical fault diagnosis.

With the development of intelligent algorithms on the Internet and the widespread application of signal recovery technology in the current mechanical industry, signal recovery systems based on fuzzy adaptive sliding mode algorithms are becoming increasingly important for improving mechanical bearing fault diagnosis. In the construction of the entire mechanical bearing signal recovery model, how to improve the accuracy of signal recovery and reduce the time for model signal feature extraction is currently a key issue that needs to be urgently solved. This article conducts simulation experiments and analysis on the parameter dataset of mechanical bearing components that are prone to faults. Based on the fuzzy adaptive sliding mode algorithm process, combined with adaptive law parameter calculation and fuzzy system model design, the following conclusion is drawn: the application of improved signal recovery models on the sampled four bearing component parameters has an average improvement of 6.65% in recovery accuracy and 9.25% in recovery efficiency. This method uses fuzzy adaptive sliding mode algorithm to adaptively extract fault features, accurately identify fault types and degrees, innovatively suppress noise and interference, and improve the accuracy of vibration signal recovery.

During the re-mining of historical residual coal resources, the stress environment is complex, the surrounding rock conditions are bad, the mining roadway is significantly affected by ground pressure, the layout is difficult, and the safety is poor. Taking the recovery of isolated island coal pillar in 4# coal seam as the research background, based on the difference in the distribution morphology of the goaf on both sides of the isolated island coal pillar, the stress and failure law of the isolated island panel boundary are studied by numerical simulation method. (1) The peak stress difference of multiple goaf boundaries on both sides of the isolated island coal pillar is between 0.18 and 4.51 MPa. The peak stress is affected by the change of the length of the roof “cantilever beam” at the stopping line of the goaf, so that the peak stress of the goaf boundary is periodic. (2) The high stress is mainly concentrated in the center of the pillar. The peak stress at the end of each pillar is 35–40 MPa. The coal pillar bears high stress, and the stress zone of the original rock moves to the end of the coal pillar. (3) There is a plastic zone of 8–20 m at the corner of the end of each coal pillar. On the basis of the stress zone and failure zone distribution of the goaf boundary on both sides of the isolated island panel, the roadway layout of the isolated island panel is determined, that is, the air-return roadway of the isolated island panel is arranged at random, and the width of the isolated island coal pillar d1 is selected as 10 m. The transport roadway is arranged straight, and the transport roadway of the isolated island panel is in the width section area of the goaf X4103. The width d1 of the isolated island coal pillar is selected to be 8 m, and the length d5–d7 of the mining roadway layout in the width of the coal pillar is 24 m. The roadway of isolated island panel is divided into 4 areas for support control, and the drilling pressure relief technology is proposed for high stress roadway. Through the field monitoring data, it can be seen that the mining roadway can meet the requirements of isolated island coal pillar recovery, which provides reference for the layout and control of abandoned coal roadway in this mine and other mines.

During the operation of drilling rigs, bolts are subjected to significant loads, rendering bolt groups vulnerable to failure due to uneven load distribution. This study investigates the multi-bolt load distribution characteristics of eight-gear and four-gear symmetric transmission mechanisms in drilling rigs. The spring stiffness method is utilized to analyze multi-bolt load distribution. A finite element model of the bolted connection is developed by integrating the structural shape and transmission mechanism. The model's accuracy is validated through a rack strain test under various loads. Based on the finite element analysis results, this study proposes an evaluation method for bolted connections using relative deformation difference. The impacts of bolt pitch, end distance, preload, and thickness of the derrick connection plate under different load positions on the connection are examined. This paper presents a methodology and conclusions that can inform the design of bolted connections for heavy-duty drive systems.

The incompleteness and lack of bearing fault data have become important problems in bearing fault diagnosis. This paper presents an intelligent fault diagnosis method for rolling bearings based on a similarity clustering multi-channel convolution neural network with the hierarchical branch (HB-SC-MCCNN). First, the relevant features are extracted by MCCNN, and combined with the similarity clustering principle, the accurate binary classification is realized in the case of insufficient labeled data. Second, the similarity clustering module and additional loss are added to the SC-MCCNN network to form a hierarchical-branch network, which simplifies the problem of fault multi-classification into binary classification with multiple steps, and to reduces the dependence on the amount of label data in multi-classification. Finally, based on the self-learning characteristics of HB-SC-MCCNN, the unlabeled data and the missing fault types in the training set are re-labeled to realize the re-training of the network. On the benchmark dataset, the comparison experiment results with several salient deep learning models show that the method proposed in this paper successfully realizes the hierarchical diagnosis of bearing faults and presents more substantial competitiveness in the case of insufficient labeled data and missing fault types.

It is well-established that the monitoring and early warning of highway geological disasters in mountainous areas has always been the focus of highway traffic development. This study aims to determine how the application of Internet of Things technology can be better used in order to improve the ability of traffic disaster prevention and reduction .The key data such as displacement changes, cracks, and rainfall were collected by the wireless intelligent sensing mountain road disaster perception network, After analysis, it was combined with the basic information gathering of mountain roads, used to build a intelligent monitoring and decision-making system. The results show that the Internet of Things technology of 5G and BeiDou Positioning Technology has certain reliability in mountain disaster monitoring, can achieve real-time accurate perception of geological disasters, disaster prediction and auxiliary decision-making, and effectively ensure the driving safety of mountain roads.

In view of the difficulty of the surrounding rock control of retaining a roadway along a goaf, this paper takes the 5504 working face of the Hongshuliang Coal Mine as the engineering context. The uniaxial compressive strength and tensile strength of concrete filling material in the retained roadway are determined by laboratory tests. Through theoretical analysis, field investigation, numerical simulation and field measurement, the distribution characteristics of deviatoric stress and damage zone of the roadway surrounding rock in the mining process of the 5504 working face are studied here. Based on the failure of rock mass element caused by deviatoric stress tensors, the study shows that the thickness of the concrete wall is 2.2 m and the compressive strength of the concrete wall can reach 10.87~11.64 MPa in 3 days to 4 days, which can meet the support strength of the retained roadway. From the position of 90 m in front of the working face to the position of 100 m behind the working face, the distribution form of the roadway surrounding rock deviatoric stress is: symmetrical butterfly shape → single butterfly shape → narrow oblique strip → oblique 8 shape → wide oblique strip shape. When the distance between the retained roadway and the working face is 49 m, the retained roadway tends to be stable. Based on the distribution characteristics of the deviatoric stress outline line and the damage zone outline line of the retained roadway surrounding rock, the retained roadway surrounding rock is divided into three regions, and the combined support technology of “bolt + anchor cable + single pillar + reinforcement combined with steel plate to strengthen concrete wall” is proposed. Through field engineering practice, the maximum displacement of roof, floor, solid coal side and concrete wall side in the retained roadway is 136.6 mm, 78.8 mm, 62.3 mm and 43.3 m, respectively, and the surrounding rock control effect of the retained roadway is good.

An N80 casing in a certain oil well was broken. After the casing was pulled out, many cracks, sand holes, and corrosion and rust marks were observed in the casing fracture. To test the cause of the fracture, failure simulation using ANSYS software was carried out. Metallographic analysis test, chemical composition analysis test, and conventional mechanical performance test of the casing body were designed, and finally the failure analysis of the casing fracture was completed. The results revealed several large-scale oxide metallurgical inclusions in the casing near the upper end of the wellhead, which reduced the strength of the casing material and caused the casing to crack at the maximum stress position. In addition to harsh service environment, the casing was subjected to strong stress, which exceeded the strength limit of the casing and eventually caused the casing to break. The casing material met the standard requirements at all parts except the fracture areas. A calculation method is proposed for the ocean current and wind force; the method has high accuracy and can be used for analyzing similar offshore conditions. To prevent accidents, it is recommended to strictly control the heat treatment process of the casing material, optimize its microstructure, test its performance before deployment, and establish a real-time analysis system. Timely adjustments should be made to the operating schedule when operating in harsh environments.

Although China has made many breakthroughs in the research and development of the technology, the most cutting-edge technology is still monopolized by international large multinational service companies. To narrow the gap with foreign technologies and learn from each other's strengths, several new foreign rotary steering system tools are discussed in detail. The typical steering mechanisms, working principles, and measurement and control systems of these rotary steering system tools are introduced in detail. The domestic progress made in borehole trajectory control technology is summarized, focusing on the analysis of the steering structure, function realization and application promotion. On the basis of summarizing the development of foreign rotary steering system tool technology and combined with new materials and new technologies in mechanical engineering, it is proposed wellbore trajectory control tools will develop in the direction of compound steering technology, in which tool spindles, bearing materials and structures, and tool intelligent research will be the future development direction, and downhole drilling robots in harsh environments will be the research ultimate goal.

Aiming at the floor heave of transportation concentrated roadway on the West Wing (TCRWW) of No. 1 Coal Seam in Danhou Mine, it affects underground coal transportation and mine safety production. First, the lithology and structure of the roadway floor were sampled and tested, and it was found that it contained clay minerals with high hydrophilicity. Secondly, starting from the mechanical mechanism of the roadway floor, a mechanical model of the roadway floor is established. By increasing the floor anchoring layer thickness m1, the floor deformation can be effectively controlled to guarantee the stability of the surrounding rock of the roadway. Thirdly, the FLAC3D numerical simulation analysis of the roadway deformation under the existing support scheme of the roadway is consistent with the measured deformation results on-site, thereby revealing that the existing support scheme and parameters are not reasonable. Finally, the unreasonable support scheme and parameters of the existing roadway were disclosed, and an antifloor arch structure was proposed: “quicklime bottom paving + prestressed anchor cable + concrete arc beam + metal mesh + C20 high-strength concrete filling.” This floor treatment plan is adopted for the industrial verification of the test section of TCRWW. Engineering practice shows that the optimized roadway support scheme has a better effect on the deformation control of the roof-to-floor and rib-to-rib, thereby effectively ensuring safe and efficient production in the mine.

为避免地面沉降引发的油气管道事故,研究沉降管道的力学特性,提出基于谐波沉降的管道力学评估方法.以中国石化某沉降管道为研究对象,通过现场测量的方法获得沉降区管道高程,利用傅里叶级数展开对不均匀沉降数据进行处理分析,获得管道谐波沉降的拟合函数.建立ANSYS有限元模型,采用土弹簧模型模拟非沉降区管道与土体相互作用关系,将谐波沉降作为位移载荷施加到沉降区管道,对含内压管道的沉降进行数值模拟,分析其应力、应变分布规律.结果表明:沉降与非沉降交界处管道应变及应力最大,基于应变的评估准则,管道运行状态为安全,为应急响应提供支撑.

Conventional methods cannot accurately predict buildup rate. In this study, an algorithm was developed to predict the geometric deflection rate of the tool considering the influence of the radial displacement of a combined bearing. Three-point geometry was used to calculate the buildup rate and its relationship with the radial displacement of the combined bearing. The relation between the maximum spindle deflection and the load of the combined bearing was also determined by treating the spindle as a statically indeterminate beam. To consider the internal structural parameters of the combined bearing, a mathematical relationship was obtained between its load and radial displacement with the Stribeck maximum rolling element load formula and Palmgren roller bearing displacement formula. The influence of the structural parameters of the combined bearing on the buildup rate was analyzed, and the results showed that the buildup rate can be increased by increasing the thickness and pre-compression of the disc spring and decreasing its diameter ratio and the radial clearance of the self-aligning roller bearing. An experimental device was used to obtain test results with different maximum spindle deflection values. In particular, the error was less than 1% when the maximum spindle deflection was more than 4 mm.

To understand the influenced range of the soil around the suction pile under the vertical load and address the calculation problem of the vertical bearing capacity of the suction pile, theoretical formula calculation and finite element simulation are used to solve the ultimate bearing capacity. The load-displacement curve of the suction pile is obtained. The vertical bearing capacity of the suction pile is about 7 000 kN, the vertical ultimate bearing capacity of the suction pile is 6 582.4 kN. Compared with the numerical analysis results, the vertical suction pile obtained by the theoretical formula has a deviation of 6.34%. Through the analysis of the yield process of the soil around the suction pile, it is found that in the initial loading, the yield mainly appears in the soil at the end of the pile. Then the yield zone at the end of the pile continues to expand. The top soil begins to yield, and gradually expands downward. And finally, the entire yield zone completely connected. The study can provide technical references for the analysis of the vertical ultimate bearing capacity of suction pile, and has certain guiding significance for the stability and safety evaluation of suction pile.