Reasonable Layout of High Drainage Roadways for Jiaojiazhai Mine

To ensure that the gas concentration at the top corner does not exceed the limit, a reasonable level of the high drainage roadway layout in Jiaojiazhai Mine should be determined. In this work, based on the actual conditions of the working face, an SF6 tracer gas was used to test the connectivity between the high drainage roadway and the working face. A discrete element analysis program was used to simulate the deformation law of the overlying strata in the goaf, and a corresponding caving control program for the surrounding rock was written based on the obtained parameters and “O” ring theory. A fluid simulation software was used to simulate and analyze five goaf models with different high drainage roadway layouts (10, 15, 20, 25, and 30 m). The gas drainage data for two layers (10 m and 20 m) of the high drainage roadway were measured. The results showed that the height of the caving zone in the goaf is approximately 20 m, and when the high drainage roadway is arranged along the roof (when the layout layer height is 10 m), the roadway will be directly connected to the working face, thus pumping fresh air to the working face. The gas extraction effect of the 20 m stratum was better than those of the other strata. The simulation results of the gas extraction were consistent with the measured data. The proposed scheme was practically applied, and its effect was found to be evident, thus solving the problem of high gas concentration at the top corner and increasing the mine output.

Deformation Analysis of an Ultra-High Arch Dam under Different Water Level Conditions Based on Optimized Dynamic Panel Clustering

During the operation period, the deformation of an ultra-high arch dam is affected by the large fluctuation of the reservoir water level. Under the dual coupling of the ultra-high dam and the complex water level conditions, the traditional variational analysis method cannot be sufficiently applied to its deformation analysis. The deformation analysis of the ultra-high arch dam, however, is very important in order to judge the dam safety state. To analyze the deformation law of different parts of an ultra-high arch dam, the panel data clustering theory is used to construct a Spatio-temporal characteristic model of dam deformation. In order to solve the difficult problem of the fluctuating displacement of dam deformation with water level effect, three displacement component indexes (absolute quantity, growing, and fluctuation) are proposed to characterize dam deformation. To further optimize the panel clustering deformation model, the objective weight coefficient of clustering comprehensive distance is calculated based on the CRITIC (CRiteria Importance Through Inter-criteria Correlation) method. The zoning rules of the ultra-high arch dam are established by using the idea of the CSP (Constraint Satisfaction Problem) index, and the complex water level of the reservoir is simulated in the whole process. Finally, the dynamic cluster analysis of dam deformation is realized. Through a case study, three typical working conditions including the rapid rise and fall of water level and the normal operation are calculated, and the deformation laws of different deformation zones are analyzed. The results show that the model can reasonably describe the deformation law of an ultra-high arch dam under different water levels, conveniently and intuitively select representative measuring points and key monitoring parts, effectively reducing the analysis workload of lots of measuring points, and improve the reliability of arch dam deformation analysis.

Research on Improvement of Cold Extrusion Technology of Connecting Screw

In order to solve the flange and dent defects in the end face of the cold extrusion of the connecting screw, the Deform3D software is used to simulate the extrusion forming process of the connecting screw, and the velocity vector is used to study the metal flow law of the part in the cold extrusion process. According to the velocity field and deformation law obtained by the simulation, the end face depression defect in the forming process is predicted. An improved production process is proposed, and the simulation results show that the new process scheme effectively eliminates the “sag” defect on the end face of the part. Finally, the extruded parts with qualified dimensional accuracy are obtained through experiments, and the results are basically consistent with the simulation results.

Finite Element Simulation and Deformation Control of High-Speed Milling of Al7050-T7451 Thin-walled Parts

Background: To reduce environmental pollution and improve resource utilization, lightweight equipment has become an important development trend of manufacturing. Therefore, thin-walled parts are being widely used in automobiles, aerospace, etc. due to their lightweight and high specific strength. However, they usually deform during machining due to poor stiffness. Objective: To reduce the machining deformation, the finite element method has been used to analyze the deformation law of thin-walled parts. Method: A 3D milling model of Al7050-T7451 thin-walled parts was established. Then, the influence of hole structure, rib, and auxiliary support on the deformation was investigated under the condition of optimized parameters. Moreover, some related patents on the research of machining deformation of thin-walled parts were also consulted. Results: The results showed that the established 3D model could accurately predict the machining deformation of thin-walled parts. The machining deformation on the edges is more severe due to holes that weaken the stiffness of thin-walled parts. Besides, ribbed slab and auxiliary support can shorten machining deformation by 71.9% and 65.2%, respectively.

A Method of Monitoring the Cross-Section Deformation of Tunnels Using the Strain Data from the Fully Distributed Optical Fibre Sensors

Fully distributed optical fiber sensing technology allows the high-density strain to measure the overall curvature and cross-section deformation of tunnels. However, there are few studies on the use of longitudinal strain along the tunnel to measure the cross-section convergence deformation, and the method of obtaining the strain along the tunnel loop is costly. To address this issue, a method of monitoring the cross-section deformation of tunnels using the strain data is proposed. First, a model of the relationship between strain and deformation in tunnels is constructed to obtain the overall settlement using the longitudinal strain. Second, based on the finite element method (FEM), the deformation law about the strain measured points and non-measured points on the cross-section of the tunnel is proposed, and on this basis, the correlation coefficient is presented. Using the product of overall settlement and correlation coefficient, the cross-section deformation at non-measured points is obtained. The results of numerical examples shown that the proposed method can effectively expand the monitoring scale and realize high-density cross-section deformation measurement of tunnels.

Application of Slope Radar (S-SAR) in Emergency Monitoring of the “11.03” Baige Landslide

On October 11 and November 3, 2018, the disaster chain of landslide-barrier lake occurred twice in Baige Village, Xizang Province. After the second sliding of the landslide, the danger of the landslide dam was eliminated by the manual excavation of the drain grooves. During this period, a ground-based interferometric synthetic aperture radar (GB-InSAR) called “S-SAR” was utilized for real-time monitoring and analyzing 48 selected target pixels on the residual deformation bodies of landslides (divided into K1, K2, and K3 deformation zones) for 8 days. Through the real-time deformation map of pixels in the monitoring area obtained by S-SAR, the ranges of five strong deformation regions were identified and delineated. Based on the apparent cumulative deformation-time curve of each target pixel, the overall deformation law of K1, K2, and K3 deformation zones could be monitored and analyzed in real time. Based on a curve graph of the deformation rate, acceleration, and time of each target pixel, the K1, K2, and K3 deformation zones were within a uniform deformation stage. Taking the target pixel point and the corresponding time in which the deformation rate and deformation acceleration had a large, abrupt jump at the same time as the position and time of the near-slip failure, the 11 positions and moments of the near-slip failure were counted. The results presented here may represent a workable reference for emergency monitoring and early warning of similar sudden geological disasters.

Effects of Process Parameters on Surface Straightness of Variable-Section Conical Parts during Hot Power Spinning

How to form high-quality variable-section thin-walled conical parts through power spinning is a key issue for superalloy spinning manufacturing. A study into the hot power spinning deformation law of variable-section thin-walled conical parts and the effects of process parameters on surface straightness of forming quality are delineated in this paper. Through the establishment of finite element (FE) models using the single-factor and orthogonal design of experiments, the effects of four key process parameters on the surface straightness have been investigated and the optimal combination of process parameters have been yielded. These key factors include spinning temperature, roller nose radius, mandrel rotation rate and roller feed ratio. The results of FE simulation have been validated through the comparison of the surface straightness of modeled parts with those measured during a spinning experiment. The results reveal that, among the studied process parameters, the spinning temperature has the greatest influence on the surface straightness, followed by the roller nose radius and mandrel rotation rate, and the roller feed ratio has the least influence on the straightness. Larger mandrel rotation rate, smaller feed ratio and suitable spinning temperature can enhance the surface straightness.

Evaluation and Deformation Control Study on the Bias Pressure of Layered Rock Tunnels

In the process of tunnel construction, the bias of layered rock mass tunnels has always been a prominent problem that troubles the construction and safe operation of tunnels. In this paper, a comprehensive method that combines monitoring technology and discrete element (3DEC) numerical simulation is proposed to analyze the deformation characteristics of the surrounding rock in the layered rock tunnel and the deformation law of the bias tunnel. The results indicate that the tunnel surrounding rock deformation in the study area showed the characteristics of bias. Based on the bias mechanism, the surrounding rock deformation law, the construction deformation control, and the optimization measures of layered rock mass in the bias tunnel were studied by means of combining monitoring technology with discrete element (3DEC) numerical simulation. Based on the research results, appropriate methods for controlling the deformation of the surrounding rock of the tunnel with comprehensive consideration of the anchor rod length, anchor rod angle, and anchor rod layout spacing were proposed. The method proposed in this paper could visually reveal the deformation characteristics of the surrounding rock of layered rock tunnels and the deformation law of bias tunnels. It could also better solve the problem of deformation control in the tunnel construction process. This approach provides a novel idea for special layered rock mass tunnel bias evaluation and deformation control parameter optimization and serves as a valuable reference for analogous engineering cases through engineering case analysis.