Instability mechanism of mining roadway passing through fault at different angles in kilometre-deep mine and control measures of roof cutting and NPR cables

The angle α between the fault strike and the axial direction of the roadway produces different damage characteristics. In this paper, the research methodology includes theoretical analyses, numerical simulations and field experiments in the context of the Daqiang coal mine located in Shenyang, China. The stability control countermeasure of "pre-splitting cutting roof + NPR anchor cable"(PSCR-NPR) is simultaneously proposed. According to the different deformation characteristics of the roadway, the faults are innovatively classified into three types, with α of type I being 0°-30°, α of type II being 30°-60°, and α of type III being 60°-90°. The full-cycle stress evolution paths during mining roadway traverses across different types of faults are investigated by numerical simulation. Different pinch angles α lead to high stress concentration areas at different locations in the surrounding rock. The non-uniform stress field formed in the shallow surrounding rock is an important reason for the instability of the roadway. The pre-cracked cut top shifted the high stress region to the deep rock mass and formed a low stress region in the shallow rock mass. The high prestressing NPR anchor cable transforms the non-uniform stress field of the shallow surrounding rock into a uniform stress field. PSCR-NPR is applied in the fault-through roadway of Daqiang mine. The low stress area of the surrounding rock was enlarged by 3-7 times, and the cumulative convergence was reduced by 45%-50%. It provides a reference for the stability control of the deep fault-through mining roadway.

Unraveling engineering disturbance effects on deformation in red-bed mudstone railway cuttings:incorporating crack-facilitated moisture diffusion

Red-bed mudstone, prevalent in southwest China, poses a formidable challenge due to its hydrophilic clay minerals, resulting in expansion, deformation, and cracking upon exposure to moisture. This study addresses uplift deformation disasters in high-speed railways by employing a moisture diffusion-deformation-fracture coupling model based on the finite-discrete element method(FDEM). The model integrates the influence of cracks on moisture diffusion. The investigation into various excavation depths reveals a direct correlation between depth and the formation of tensile cracks at the bottom of the railway cutting. These cracks expedite moisture migration, significantly impacting the temporal and spatial evolution of the moisture field. Additionally, crack expansion dominates hygroscopic deformation, with the lateral coordinate of the crack zone determining peak vertical displacement. Furthermore, key factors influencing deformation in railway cuttings, including the swelling factor and initial moisture content at the bottom of the cutting, are explored. The number of tensile and shear cracks increases with greater excavation depth, particularly concerning shear cracks. Higher swelling factors and initial moisture contents result in an increased total number of cracks, predominantly shear cracks. Numerical calculations provide valuable insights, offering a scientific foundation and directional guidance for the precise prevention, control, prediction, and comprehensive treatment of mudstone-related issues in high-speed railways.

Assessing cutter-rock interaction during TBM tunnelling in granite:Large-scale standing rotary cutting tests and 3D DEM simulations

The widespread utilisation of tunnel boring machines(TBMs)in underground construction engineering requires a detailed investigation of the cutter-rock interaction.In this paper,we conduct a series of largescale standing rotary cutting tests on granite in conjunction with high-fidelity numerical simulations based on a particle-type discrete element method(DEM)to explore the effects of key cutting parameters on the TBM cutter performance and the distribution of cutter-rock contact stresses.The assessment results of cutter performance obtained from the cutting tests and numerical simulations reveal similar dependencies on the key cutting parameters.More specifically,the normal and rolling forces exhibit a positive correlation with penetration but are slightly influenced by the cutting radius.In contrast,the side force decreases as the cutting radius increases.Additionally,the side force shows a positive relationship with the penetration for smaller cutting radii but tends to become negative as the cutting radius increases.The cutter's relative effectiveness in rock breaking is significantly impacted by the penetration but shows little dependency on the cutting radius.Consequently,an optimal penetration is identified,leading to a low boreability index and specific energy.A combined Hertz-Weibull function is developed to fit the cutter-rock contact stress distribution obtained in DEM simulations,whereby an improved CSM(Colorado School of Mines)model is proposed by replacing the original monotonic cutting force distribution with this combined Hertz-Weibull model.The proposed model outperforms the original CSM model as demonstrated by a comparison of the estimated cutting forces with those from the tests/simulations.The findings from this work that advance our understanding of TBM cutter performance have important implications for improving the efficiency and reliability of TBM tunnelling in granite.

Precipitates Generation Mechanism and Surface Quality Improvement for Aluminum Alloy 6061 in Diamond Cutting

To improve the surface quality for aluminum alloy 6061(Al6061) in ultra-precision machining, we investigated the factors affecting the surface finish in single point diamond turning(SPDT)by studying influence of the precipitates generation of Al6061 on surface integrity and surface roughness.Based on the Johnson-Mehl-Avrami solid phase transformation kinetics equation, theoretical and experimental studies were conducted to build the relationship between the aging condition and the type, size and number of the precipitates for Al6061. Diamond cutting experiments were conducted to machine Al6061 samples under different aging conditions. The experimental results show that, the protruding on the chip surface is mainly Mg_(2)Si and the scratches on the machined surface mostly come from the iron-containing phase(α-, β-AlFeSi).Moreover, the generated Mg_(2)Si and α-, β-AlFeSi affect the surface integrity and the diamond turned surface roughness. Especially, the achieved surface roughness in SPDT is consistent with the variation of the number of AlFeSi and Mg_(2)Si with the medium size(more than 1 μm and less than 2 μm) in Al6061.

Hole cleaning evaluation and installation spacing optimization of cuttings bed remover in extended-reach drilling

In extended-reach or long-horizontal drilling,cuttings usually deposit at the bottom of the annulus.Once cuttings accumulate to a certain thickness,complex problems such as excessive torque and drag,tubing buckling,and pipe stuck probably occur,which results in a lot of non-productive time and remedial operations.Cuttings bed remover can efficiently destroy deposited cuttings in time through hydraulic and mechanical stirring effects.This paper aims to build a method for hole cleaning evaluation and installation spacing optimization of cuttings bed remover to improve the wellbore cleaning effect.Firstly,a Computational Fluid Dynamics approach with Eulerian—Eulerian multiphase model was utilized to investigate the mechanism of cuttings transportation,and a new type of cuttings bed remover was designed.Next,an evaluation method of hole cleaning effect of remover was established.After that,the effects of several drilling parameters on hole cleaning including flow rate of drilling fluid,rotational speed of drillpipe,rate of penetration,wellbore size,rheological property of drilling fluid,and remover eccentricity on the performance of cuttings bed remover were investigated.The results demonstrate that the new type of remover with streamline blade performs better than conventional removers.The efficiency of hole cleaning is greatly improved by increasing the rotational speed of drillpipe,flow rate of drilling fluid,remover eccentricity,and 6 rpm Fann dial reading for drilling fluid.While higher rate of penetration and large wellbore size result in worse hole cleaning.These findings can serve as an important guide for the structure optimization design of cuttings bed remover and installation spacing of removers.

Ground response and failure mechanism of gob-side entry by roof cutting with hard main roof

This study is the result of long-term efforts of the authors’team to assess ground response of gob-side entry by roof cutting(GSERC)with hard main roof,aiming at scientific control for GSERC deformation.A comprehensive field measurement program was conducted to determine entry deformation,roof fracture zone,and anchor bolt(cable)loading.The results indicate that GSERC deformation presents asymmetric characteristics.The maximum convergence near roof cutting side is 458 mm during the primary use process and 1120 mm during the secondary reuse process.The entry deformation is closely associated with the primary development stage,primary use stage,and secondary reuse stage.The key block movement of roof cutting structure,a complex stress environment,and a mismatch in the supporting design scheme are the failure mechanism of GSERC.A controlling ideology for mining states,including regional and stage divisions,was proposed.Both dynamic and permanent support schemes have been implemented in the field.Engineering practice results indicate that the new support scheme can efficiently ensure long-term entry safety and could be a reliable approach for other engineering practices.

Yield and Nutritive Values of Semi- and Non-Fall Dormant Alfalfa Cultivars under Late-Cutting Schedule in California’s Central Valley

California is one of the major alfalfa (Medicago sativa L) forage-producing states in the U.S, but its production area has decreased significantly in the last couple of decades. Selection of cultivars with high yield and nutritive value under late-cutting schedule strategy may help identify cultivars that growers can use to maximize yield while maintaining area for sustainable alfalfa production, but there is little information on this strategy. A field study was conducted to determine cumulative dry matter (DM) and nutritive values of 20 semi- and non-fall dormant (FD) ratings (FD 7 and FD 8 - 10, respectively) cultivars under 35-day cut in California’s Central Valley in 2020-2022. Seasonal cumulative DM yields ranged from 6.8 in 2020 to 37.0 Mg·ha−1 in 2021. Four FD 8 - 9 cultivars were the highest yielding with 3-yrs avg. DM greater than the lowest yielding lines by 46%. FD 7 cultivar “715RR” produced the highest crude protein (CP: 240 g·Kg−1) while FD 8 cultivar “HVX840RR” resulted in the highest neutral detergent fiber digestibility (NDFD: 484 g·Kg−1, 7% greater than the top yielding cultivars) but with DM yield intermediate. Yields and NDFD correlated positively but weakly indicating some semi- and non-FD cultivars performing similarly. These results suggest that selecting high yielding cultivars under 35-day cutting schedule strategy can be used as a tool to help growers to maximize yield while achieving good quality forages for sustainable alfalfa production in California’s Central Valley.

Endoscopic radial incision and cutting method for adult congenital duodenal webs:A case report

BACKGROUND Congenital duodenal webs are rare in adults and can lead to various symptoms such as nausea,vomiting,and postprandial fullness.The treatment for this disease is mostly surgical.Endoscopic treatment techniques have been developed and attempted for this disease.Endoscopic radial incision and cutting(RIC)techniques are reportedly very effective in benign anastomotic stricture.This case report highlights the effectiveness and safety of endoscopic RIC as a minimally invasive treatment for adult congenital duodenal webs.CASE SUMMARY A 23-year-old female patient with indigestion was referred to a tertiary hospital.The patient complained of postprandial fullness in the epigastric region.Previous physical examinations or blood tests indicated no abnormalities.Computed tomography revealed an eccentric broad-based delayed-enhancing mass-like lesion in the second portion of the duodenum.Endoscopy showed an enlarged gastric cavity and a significantly dilated duodenal bulb;a very small hole was observed in the distal part of the second portion,and scope passage was not possible.Gastrografin upper gastrointestinal series was performed,revealing an intraduodenal barium contrast-filled sac with a curvilinear narrow radiolucent rim,a typical"windsock"sign.Endoscopic RIC was performed on the duodenal web.The patient recovered uneventfully.Follow-up endoscopy showed a patent duodenal lumen without any residual stenosis.The patient reported complete resolution of symptoms at the 18-month follow-up.CONCLUSION Endoscopic RIC may be an effective treatment for congenital duodenal webs in adults.

Cutting Propagation Technique of Pennisetum purpureum Schum

[Objectives]The paper was to study the cutting propagation technique of Pennisetum purpureum Schum and to provide a technical reference for establishing an efficient cutting propagation method.[Methods]Six treatments were set up using P.purpureum cv.Guiminyin and P.purpureum cv.Guimu-1 as test materials,including 1-node oblique insertion,1-node oblique insertion+rooting powder,1-node transverse burial,2-node oblique insertion,2-node oblique insertion+rooting powder and 2-node transverse burial.The following indices were observed and determined for P.purpureum cuttings:emergence rate,rooting rate,root number,longest root length,fresh root weight,plant height,number of tillers,number of leaves,and fresh stem and leaf weight.[Results]In the 2-node cutting+rooting powder treatment,Guiminyin and Guimu-1 exhibited the highest survival rate,root growth indices,and stem and leaf growth indices,with the emergence rates of 94.29%and 90.26%,respectively.The 2-node cutting treatment followed closely behind,while the 1-node cutting treatment had the lowest indices.Under the same treatment,Guimuyin exhibited higher mean values for plant height,number of leaves,fresh stem and leaf weight,longest root length,and fresh root weight compared to Guimu-1.However,it had lower mean number of tillers,and emergence rate and rooting rate of the 1-node cutting treatment compared to Guimu-1.[Conclusions]The P.purpureum cuttings thrived in the 2-node cutting+rooting powder treatment,and the overall cutting effect of Guiminyin was superior to that of Guimu-1.

Application of Fuyang Paper Cutting Art in Cultural and Creative Design from the Perspective of Rural Revitalization

The application significance of Fuyang paper cutting art in cultural and creative design from the perspective of rural revitalization was discussed,and the implementation principles and specific practices of applying the elements and techniques of Fuyang traditional paper cutting art in cultural and creative products with local features were analyzed to provide reference for rural revitalization and development of cultural industry.

Cutting-edge Technological Innovation Outcome Displayed at 2024 Beijing Science and Technology Week

The 2024 National Science and Technology Week and Beijing Science and Technology Week opened in Shougang Park in Shijingshan District from May 25 to June 1.Under the theme of“Carrying forward the spirit of scientists and inspiring societal innovation,”this event focused on the new-generation IT technology,medical health,energy and technology,modern agriculture and intelligent manufacturing industries.

Research on the Resistance of Cutting Mechanism of Mining Longitudinal Roadheader

In order to accurately obtain the dynamic characteristics of the cutting mechanism of the mining longitudinal roadheader,combined with the working principle of the mining longitudinal roadheader,the theoretical analysis and derivation are carried out in detail.By using ADAMS to simulate,the resistance curve and torque curve of the cutting mechanism in different directions are obtained.The results show that ADAMS can effectively predict the excavation resistance and torque of the cutting mechanism of mining longitudinal roadheader,which has certain reference value for future optimization design.

Design and Numerical Simulation of Dust Removal System for Sutomotive Iongitudinal Beam Plasma Cutting

To improve the poor efficiency of the dust removal system in the plasma cutting station of automotive longitudinal beams,and reduce the cutting surface quality degradation due to dust,a bottom-side suction dust removal system is designed,and the dust removal effect is optimized through the setting of the following dampers and diversion plates.The result of numerical simulation indicates that the particle collection rate can reach 99.44%,and the field test also proves the effectiveness of the dust removal system,which is of guiding significance for the transformation of other similar dust removal systems.

Research on the cutting thermodynamic behavior of high-strength large-thickness offshore jack-up platform leg rack

The cutting of offshore jack-up platform leg rack is highly nonlinear and complex thermal processing process. The residual stress influences the following welding quality and cause crack growth. Therefore, research on the cutting practice of jack-up platform leg rack is significant to improve the safety and reliability of the offshore platform. A heating source model that is applicable to the cutting and emulation of high-strength thick plates han been presented. Then, the thermo-physical characteristic parameters of NV E690 leg plate was calculated by JMATPRO, and is revised according to the theory of metallographic. Furthermore, the numerical simulation of the linear cutting of leg plate was conducted, and the reliability of the heating source model and the thermo-physical characteristic parameters of material were proved by comparing them with the experimental data. Bused on the former study, the optimal parameter （ heating source, cutting speed and radius of the heating source model） which ensured that the gear plate was cut through without edge collapses during cutting was calculated. The optimized process parameters can be used to study the distribution of residual stress in gear plate during cutting which provides theoretical guideline for improving the construction technology of offshore platform legs.

Friction behaviors in the metal cutting process:state of the art and future perspectives

Material removal in the cutting process is regarded as a friction system with multiple input and output variables.The complexity of the cutting friction system is caused by the extreme conditions existing on the tool–chip and tool–workpiece interfaces.The critical issue is significant to use knowledge of cutting friction behaviors to guide researchers and industrial manufacturing engineers in designing rational cutting processes to reduce tool wear and improve surface quality.This review focuses on the state of the art of research on friction behaviors in cutting procedures as well as future perspectives.First,the cutting friction phenomena under extreme conditions,such as high temperature,large strain/strain rates,sticking–sliding contact states,and diverse cutting conditions are analyzed.Second,the theoretical models of cutting friction behaviors and the application of simulation technology are discussed.Third,the factors that affect friction behaviors are analyzed,including material matching,cutting parameters,lubrication/cooling conditions,micro/nano surface textures,and tool coatings.Then,the consequences of the cutting friction phenomena,including tool wear patterns,tool life,chip formation,and the machined surface are analyzed.Finally,the research limitations and future work for cutting friction behaviors are discussed.This review contributes to the understanding of cutting friction behaviors and the development of high-quality cutting technology.

Numerical simulation of materials-oriented ultra-precision diamond cutting:review and outlook

Ultra-precision diamond cutting is a promising machining technique for realizing ultra-smooth surface of different kinds of materials.While fundamental understanding of the impact of workpiece material properties on cutting mechanisms is crucial for promoting the capability of the machining technique,numerical simulation methods at different length and time scales act as important supplements to experimental investigations.In this work,we present a compact review on recent advancements in the numerical simulations of material-oriented diamond cutting,in which representative machining phenomena are systematically summarized and discussed by multiscale simulations such as molecular dynamics simulation and finite element simulation:the anisotropy cutting behavior of polycrystalline material,the thermo-mechanical coupling tool-chip friction states,the synergetic cutting responses of individual phase in composite materials,and the impact of various external energetic fields on cutting processes.In particular,the novel physics-based numerical models,which involve the high precision constitutive law associated with heterogeneous deformation behavior,the thermo-mechanical coupling algorithm associated with tool-chip friction,the configurations of individual phases in line with real microstructural characteristics of composite materials,and the integration of external energetic fields into cutting models,are highlighted.Finally,insights into the future development of advanced numerical simulation techniques for diamond cutting of advanced structured materials are also provided.The aspects reported in this review present guidelines for the numerical simulations of ultra-precision mechanical machining responses for a variety of materials.

Stability control measures for roof cutting and NPR supporting of mining roadways in fault areas of kilometre-deep coal mine

The study focuses on the stability control measures for mining roadways in fault zones of deep mines,using Daqiang Coal Mine as a case study.The control system under consideration,referred to as"pre-splitting cutting roof+NPR anchor cable"(PSCR-NPR),is subjected to scrutiny through theoretical analysis,numerical modelling,and field trials.Furthermore,a comprehensive analysis is undertaken to evaluate the stability control mechanism of this particular technology.The study provides evidence that the utilization of deep-hole directional energy-concentrated blasting facilitates the attainment of directional roof cutting in roadways.The aforementioned procedure leads to the formation of a uniform structural surface on the roof of the roadway and causes modifications in the surrounding geological formation.The examination of the lateral abutment pressure and shear stress distribution,both prior to and subsequent to roof cutting,indicates that the implementation of pre-splitting techniques leads to a noteworthy reduction in pressure.The proposition of incorporating the safety factor Q for roof cutting height is suggested as a method to augment comprehension of the pressure relief phenomenon in the field of engineering.The analysis of numerical simulation has indicated that the optimal pressure relief effect of a mining roadway in a fault area is attained when the value of Q is 1.8.The NPR anchor cable exhibits noteworthy characteristics,including a high level of prestress,continuous resistance,and substantial deformation.After the excavation of the roadway,a notable reduction in radial stress occurs,leading to the reinstatement of the three-phase stress state in the surrounding rock.This restoration is attributed to the substantial prestress exerted on the radial stress.The termination point of the NPR anchor cable is strategically positioned within a stable rock formation,allowing for the utilization of the mechanical characteristics of the deep stable rock mass.This positioning serves to improve the load-bearing capacity of the surrounding rock.The mining roadway within the fault region of Daqiang Coal Mine is outfitted with the PSCR-NPR technology.The drop in shear stress experienced by the rock surrounding the roadway is estimated to be around 30%,whilst the low-stress region of the mining roadway extends by a factor of approximately 5.5.The magnitude of surface displacement convergence experiences a decrease of approximately 45%-50%.The study’s findings provide useful insights regarding the stable of mining roadway in characterized by fault zones.

Performances of a Stinger PDC cutter breaking granite: Cutting force and mechanical specific energy in single cutter tests

The Stinger PDC cutter has high rock-breaking efficiency and excellent impact and wear resistance, which can significantly increase the rate of penetration (ROP) and extend PDC bit life for drilling hard and abrasive formation. The knowledge of force response and mechanical specific energy (MSE) for the Stinger PDC cutter is of great importance for improving the cutter's performance and optimizing the hybrid PDC bit design. In this paper, 87 single cutter tests were conducted on the granite. A new method for precisely obtaining the rock broken volume was proposed. The influences of cutting depth, cutting angle, and cutting speed on cutting force and MSE were analyzed. Besides, a phenomenological cutting force model of the Stinger PDC cutter was established by regression of experimental data. Moreover, the surface topography and fracture morphology of the cutting groove and large size cuttings were measured by a 3D profilometer and a scanning electron microscope (SEM). Finally, the rock-breaking mechanism of the Stinger PDC cutter was illustrated. The results indicated that the cutting depth has the greatest influence on the cutting force and MSE, while the cutting speed has no obvious effects, especially at low cutting speeds. As the increase of cutting depth, the cutting force increases linearly, and MSE reduces with a quadratic polynomial relationship. When the cutting angle raises from 10° to 30°, the cutting force increases linearly, and the MSE firstly decreases and then increases. The optimal cutting angle for breaking rock is approximately 20°. The Stinger PDC cutter breaks granite mainly by high concentrated point loading and tensile failure, which can observably improve the rock breaking efficiency. The key findings of this work will help to reveal the rock-breaking mechanisms and optimize the cutter arrangement for the Stinger PDC cutter.

Effects of Root Cutting on Morphological Characteristics and Endogenous Hormone Levels of Quercus variabilis Seedlings

The objective of this study was to investigate the effects of root cutting stress on the dynamic changes of endogenous hormone content and growth characteristics of Quercus variabilis roots,and to explore the physiological role of endogenous hormones in regulating root-crown interactions in the short term.The morphological characteristics and endogenous hormone contents of normal roots(no root cutting,CK)and cut roots(cut by 1/3 of the length of the main root,RP)were determined by liquid chromatography,which was combined with mass spectrometry at different levels of different developmental stages.The results showed that the root growth indexes and root endogenous hormones in the RP group were superior to those in the CK group.Through comprehensive analysis of endogenous hormones,it was found that the crosstalk of IAA,JA,ABA and SA could activate the root growth defense.After the root cutting treatment,the root growth of Quercus variabilis seedlings could compensate for the inhibition of taproot growth by promoting lateral root growth.The growth and development of compensatory lateral roots contribute to the increase the total root length of plants,thus promoting the absorption of water and nutrients.It is speculated that plant hormones may be the key factors affecting their development,but this is not only related to the content of a single hormone,but more importantly,it is the interaction between various hormones.

Experimental research and application of cold cutting to hot stamping parts based on multiphase microstructure

Among the bottlenecks that hinder the improvement of the production efficiency of hot stamping are high strength and difficulty in edge cutting and hole punching.Starting from the preparation of hot stamping multiphase microstructure materials,this paper developed a plate quenching die system with controllable surface temperature and prepared four types of hot stamping plates with different martensite volume fractions.Then,straight edge cold cutting experiments were performed to study the influence of cutting clearance and cutting force on fracture quality.The results show that the bright zone is the largest when the cutting clearance is 0.14 mm,and the cutting experience coefficient of the hot stamping sheet with each martensite volume fraction is obtained when the cutting clearance is 0.14 mm.The research results of this paper were applied to the production of hot stamping parts.