越野车辆在软土路面上行驶时,其车轮-地面相互作用的动态力学行为极其复杂,车轮的下陷程度和通行能力均为车辆地面力学研究的重点。为探究车轮在软土路面通行时的动力学性能,本文提出了一种连续-非连续单元法(Continu⁃ous-discontinuous...越野车辆在软土路面上行驶时,其车轮-地面相互作用的动态力学行为极其复杂,车轮的下陷程度和通行能力均为车辆地面力学研究的重点。为探究车轮在软土路面通行时的动力学性能,本文提出了一种连续-非连续单元法(Continu⁃ous-discontinuous Element Method,CDEM)与颗粒离散元法(Discrete Element Method,DEM)相结合的耦合计算方法。该方法中,车轮采用CDEM单元进行描述,软土路面采用DEM颗粒进行描述,CDEM单元与DEM颗粒之间采用罚弹簧进行耦合,通过在车轮上施加动态扭矩,实现了车轮在软土路面上摩擦、滚动及前行过程的精确模拟。借助CDEM与DEM的耦合,探讨了车轮花纹、路障对车辆行驶过程中动力学行为的影响规律。研究结果表明:花纹车轮及光面车轮均在软土路面留下清晰可见的车辙;花纹轮胎较光面轮胎表现出更强的通行能力;花纹车轮转动速度较小,但其车轮平动速度远高于光面车轮,花纹车轮平动与其线速度之比约为12.78%,而光面车轮比值仅为2.80%;车轮在软土路面行驶过程中,相同质量下的光面车轮下陷深度远高于花纹车轮;车辆在含路障路面通行时,地面起伏度与车辆行驶能耗之间密切相关,起伏度越大,所需能量越大。展开更多
载荷装备通过软土地面会引起了软土地面的变形,车轮侵入软土的深度是软土地面装备通行性评估的重要参数。本文提出了连续-非连续单元法(Continuum-discontinuum Element Method,CDEM)与物质点法(Material Point Meth⁃od,MPM)耦合的数值...载荷装备通过软土地面会引起了软土地面的变形,车轮侵入软土的深度是软土地面装备通行性评估的重要参数。本文提出了连续-非连续单元法(Continuum-discontinuum Element Method,CDEM)与物质点法(Material Point Meth⁃od,MPM)耦合的数值计算方法,建立了车轮-软土地面耦合模型,模拟了车轮和软土地面相互作用过程,定量分析车轮载重、软土弹性模量、软土强度参数(黏聚力、摩擦角)与软土表面压应力、侵入深度等参数之间的关系,获得车轮侵入软土深度的变化规律。研究表明:软土侵入深度与车轮载重接近线性正相关,相对改变量约为179%;与弹性模量非线性负相关,相对改变量约为23%;与强度参数非线性负相关,相对改变量约为164%。当车轮载重一定时,非线性变化的车轮侵入深度对软土强度参数更敏感。建立强度参数(黏聚力、摩擦角)和侵入深度变化的三维关系,可为软土地面装备通行性评估中现场待测的关键参数提供理论依据。展开更多
Continuum-based discrete element method(CDEM)is an explicit numerical method used for simulation of progressive failure of geological body.To improve the efficiency of contact detection and simplify the calculation st...Continuum-based discrete element method(CDEM)is an explicit numerical method used for simulation of progressive failure of geological body.To improve the efficiency of contact detection and simplify the calculation steps for contact forces,semi-spring and semi-edge are introduced in calculation.Semispring is derived from block vertex,and formed by indenting the block vertex into each face(24semisprings for a hexahedral element).The formation process of semi-edge is the same as that of semi-spring(24semi-edges for a hexahedral element).Based on the semi-springs and semi-edges,a new type of combined contact model is presented.According to this model,six contact types could be reduced to two,i.e.the semi-spring target face contact and semi-edge target edge contact.By the combined model,the contact force could be calculated directly(the information of contact type is not necessary),and the failure judgment could be executed in a straightforward way(each semi-spring and semi-edge own their characteristic areas).The algorithm has been successfully programmed in C++program.Some simple numerical cases are presented to show the validity and accuracy of this model.Finally,the failure mode,sliding distance and critical friction angle of Jiweishan landslide are studied with the combined model.展开更多
近年来,矿产资源的开采状态由露天转地下,由浅部转深部,在深部岩体的钻爆法施工中,地应力对爆破效果有显著影响。有关掏槽爆破机理和应用的研究主要是针对浅部地层中的巷道爆破施工,没有考虑地应力对爆破效果的作用。采用一种考虑爆破...近年来,矿产资源的开采状态由露天转地下,由浅部转深部,在深部岩体的钻爆法施工中,地应力对爆破效果有显著影响。有关掏槽爆破机理和应用的研究主要是针对浅部地层中的巷道爆破施工,没有考虑地应力对爆破效果的作用。采用一种考虑爆破荷载下粉碎区能量耗散的改进型连续-非连续单元法(Continuum-Discontinuum Element Method,CDEM),基于二维平面应变模型,分别研究了普通直眼掏槽爆破和大空孔直眼掏槽爆破在不同地应力条件下的应力演化过程和破裂损伤特征。数值模拟结果表明,大空孔的存在增强了爆炸应力波的反射拉伸作用,削弱了地应力对爆炸裂纹扩展的抑制作用,促进了爆炸主裂纹的扩展,增加了掏槽爆破的分形损伤和损伤面积,提高了掏槽爆破的岩体破碎程度。双向等压地应力对爆炸裂纹的扩展有抑制作用,对径向爆炸裂纹的扩展尤为显著。较大的地应力削弱了孔间爆炸应力波的相互作用,相邻炮孔对爆炸主裂纹扩展的导向效应减弱。随着地应力的增加,爆炸裂纹的分形维数和分形损伤整体上呈逐渐减小的趋势,但是大空孔直眼掏槽爆破的裂隙区分形损伤和损伤面积均显著大于普通直眼掏槽爆破的裂隙区分形损伤和损伤面积。说明在高地应力环境下,大空孔直眼掏槽爆破依然能够显著增加岩石破碎程度和破碎范围,提高爆破效果和破碎效率。展开更多
Perforation is a pivotal technique employed to establish main flow channels within the reservoir formation at the outset of hydraulic fracturing operations.Optimizing perforation designs is critical for augmenting the...Perforation is a pivotal technique employed to establish main flow channels within the reservoir formation at the outset of hydraulic fracturing operations.Optimizing perforation designs is critical for augmenting the efficacy of hydraulic fracturing and boosting oil or gas production.In this study,we employ a hybrid finite-discrete element method,known as the continuous–discontinuous element method(CDEM),to simulate the initiation of post-perforation hydraulic fractures and to derive enhanced design parameters.The model incorporates the four most prevalent perforation geometries,as delineated in an engineering technical report.Real-world perforations deviate from the ideal cylindrical shape,exhibiting variable cross-sectional profiles that typically manifest as an initial constriction followed by an expansion,a feature consistent across all four perforation types.Our simulations take into account variations in perforation hole geometries,cross-sectional diameters,and perforation lengths.The findings show that perforations generated by the 39g DP3 HMX perforating bullet yield the lowest breakdown pressure,which inversely correlates with increases in sectional diameter and perforation length.Moreover,this study reveals the relationship between breakdown pressure and fracture degree,providing valuable insights for engineers and designers to refine perforation strategies.展开更多
文摘越野车辆在软土路面上行驶时,其车轮-地面相互作用的动态力学行为极其复杂,车轮的下陷程度和通行能力均为车辆地面力学研究的重点。为探究车轮在软土路面通行时的动力学性能,本文提出了一种连续-非连续单元法(Continu⁃ous-discontinuous Element Method,CDEM)与颗粒离散元法(Discrete Element Method,DEM)相结合的耦合计算方法。该方法中,车轮采用CDEM单元进行描述,软土路面采用DEM颗粒进行描述,CDEM单元与DEM颗粒之间采用罚弹簧进行耦合,通过在车轮上施加动态扭矩,实现了车轮在软土路面上摩擦、滚动及前行过程的精确模拟。借助CDEM与DEM的耦合,探讨了车轮花纹、路障对车辆行驶过程中动力学行为的影响规律。研究结果表明:花纹车轮及光面车轮均在软土路面留下清晰可见的车辙;花纹轮胎较光面轮胎表现出更强的通行能力;花纹车轮转动速度较小,但其车轮平动速度远高于光面车轮,花纹车轮平动与其线速度之比约为12.78%,而光面车轮比值仅为2.80%;车轮在软土路面行驶过程中,相同质量下的光面车轮下陷深度远高于花纹车轮;车辆在含路障路面通行时,地面起伏度与车辆行驶能耗之间密切相关,起伏度越大,所需能量越大。
文摘载荷装备通过软土地面会引起了软土地面的变形,车轮侵入软土的深度是软土地面装备通行性评估的重要参数。本文提出了连续-非连续单元法(Continuum-discontinuum Element Method,CDEM)与物质点法(Material Point Meth⁃od,MPM)耦合的数值计算方法,建立了车轮-软土地面耦合模型,模拟了车轮和软土地面相互作用过程,定量分析车轮载重、软土弹性模量、软土强度参数(黏聚力、摩擦角)与软土表面压应力、侵入深度等参数之间的关系,获得车轮侵入软土深度的变化规律。研究表明:软土侵入深度与车轮载重接近线性正相关,相对改变量约为179%;与弹性模量非线性负相关,相对改变量约为23%;与强度参数非线性负相关,相对改变量约为164%。当车轮载重一定时,非线性变化的车轮侵入深度对软土强度参数更敏感。建立强度参数(黏聚力、摩擦角)和侵入深度变化的三维关系,可为软土地面装备通行性评估中现场待测的关键参数提供理论依据。
基金the National Basic Research Program of the Ministry of Science and Technology of China (Grant No. 2010CB731506)the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (Grant No. 2012BAK10B01)the Youth Science Fund of National Natural Science Foundation of China (Grant No. 11302230)
文摘Continuum-based discrete element method(CDEM)is an explicit numerical method used for simulation of progressive failure of geological body.To improve the efficiency of contact detection and simplify the calculation steps for contact forces,semi-spring and semi-edge are introduced in calculation.Semispring is derived from block vertex,and formed by indenting the block vertex into each face(24semisprings for a hexahedral element).The formation process of semi-edge is the same as that of semi-spring(24semi-edges for a hexahedral element).Based on the semi-springs and semi-edges,a new type of combined contact model is presented.According to this model,six contact types could be reduced to two,i.e.the semi-spring target face contact and semi-edge target edge contact.By the combined model,the contact force could be calculated directly(the information of contact type is not necessary),and the failure judgment could be executed in a straightforward way(each semi-spring and semi-edge own their characteristic areas).The algorithm has been successfully programmed in C++program.Some simple numerical cases are presented to show the validity and accuracy of this model.Finally,the failure mode,sliding distance and critical friction angle of Jiweishan landslide are studied with the combined model.
基金the National Natural Science Foundation of China(Grant No.12072347)the Excellent Training Plan of the Institute of Mechanics,Chinese Academy of Sciences,and CNPC New Energy Key Project(Grant No.2021DJ4902).
文摘近年来,矿产资源的开采状态由露天转地下,由浅部转深部,在深部岩体的钻爆法施工中,地应力对爆破效果有显著影响。有关掏槽爆破机理和应用的研究主要是针对浅部地层中的巷道爆破施工,没有考虑地应力对爆破效果的作用。采用一种考虑爆破荷载下粉碎区能量耗散的改进型连续-非连续单元法(Continuum-Discontinuum Element Method,CDEM),基于二维平面应变模型,分别研究了普通直眼掏槽爆破和大空孔直眼掏槽爆破在不同地应力条件下的应力演化过程和破裂损伤特征。数值模拟结果表明,大空孔的存在增强了爆炸应力波的反射拉伸作用,削弱了地应力对爆炸裂纹扩展的抑制作用,促进了爆炸主裂纹的扩展,增加了掏槽爆破的分形损伤和损伤面积,提高了掏槽爆破的岩体破碎程度。双向等压地应力对爆炸裂纹的扩展有抑制作用,对径向爆炸裂纹的扩展尤为显著。较大的地应力削弱了孔间爆炸应力波的相互作用,相邻炮孔对爆炸主裂纹扩展的导向效应减弱。随着地应力的增加,爆炸裂纹的分形维数和分形损伤整体上呈逐渐减小的趋势,但是大空孔直眼掏槽爆破的裂隙区分形损伤和损伤面积均显著大于普通直眼掏槽爆破的裂隙区分形损伤和损伤面积。说明在高地应力环境下,大空孔直眼掏槽爆破依然能够显著增加岩石破碎程度和破碎范围,提高爆破效果和破碎效率。
基金support from the National Natural Science Foundation of China(Grant Nos.52178324,12102059)the China Postdoctoral Science Foundation(Grant No.2023M743604)+1 种基金the Beijing Natural Science Foundation(Grant No.3212027),the National Key R&D Program of China(Grant No.2023YFC3007203)the 2019 Foreign Experts Plan of Hebei Province.
文摘Perforation is a pivotal technique employed to establish main flow channels within the reservoir formation at the outset of hydraulic fracturing operations.Optimizing perforation designs is critical for augmenting the efficacy of hydraulic fracturing and boosting oil or gas production.In this study,we employ a hybrid finite-discrete element method,known as the continuous–discontinuous element method(CDEM),to simulate the initiation of post-perforation hydraulic fractures and to derive enhanced design parameters.The model incorporates the four most prevalent perforation geometries,as delineated in an engineering technical report.Real-world perforations deviate from the ideal cylindrical shape,exhibiting variable cross-sectional profiles that typically manifest as an initial constriction followed by an expansion,a feature consistent across all four perforation types.Our simulations take into account variations in perforation hole geometries,cross-sectional diameters,and perforation lengths.The findings show that perforations generated by the 39g DP3 HMX perforating bullet yield the lowest breakdown pressure,which inversely correlates with increases in sectional diameter and perforation length.Moreover,this study reveals the relationship between breakdown pressure and fracture degree,providing valuable insights for engineers and designers to refine perforation strategies.
