Shale reservoirs are characterized by numerous geological discontinuities,such as bedding planes,and exhibit pronounced heterogeneity across rock layers separated by these planes.Bedding planes often possess distinct ...Shale reservoirs are characterized by numerous geological discontinuities,such as bedding planes,and exhibit pronounced heterogeneity across rock layers separated by these planes.Bedding planes often possess distinct mechanical properties compared to the surrounding rock matrix,particularly in terms of damage and fracture behavior.Consequently,vertical propagation of hydraulic fractures is influenced by both bedding planes and the heterogeneity.In this study,a numerical investigation into the height growth of hydraulic fractures was conducted using the finite element method,incorporating zero-thickness cohesive elements.The analysis explored the effects of bedding planes,toughness contrasts between layers,and variations in in-situ stress across different strata.The results reveal that hydraulic fractures are more likely to propagate along bedding planes instead of traversing them and extending vertically into barrier layers when(1)bedding strength is low,(2)stress contrast between layers is high,and(3)toughness contrast is significant.Furthermore,for a given bedding strength,increased stress contrast or higher toughness contrast between layers elevate hydraulic fracture extension pressure.When a substantial stress difference exists between layers(Lc 0.4),hydraulic=fractures preferentially propagate along bedding planes.Conversely,as bedding strength increases,the propagation distance along bedding planes decreases,accompanied by an amplified horizontal compressive stress field.Notably,when the stress difference is sufficiently small(SD a phenomenon termed“stress rolling”emerges,wherein<-0.2),hydraulic fractures deviate from vertical growth and instead extend along a near-horizontal trajectory.展开更多
煤矿井下作业环境复杂多变,钻探成为煤矿开采的必备环节。钻杆加卸是钻探过程中的重要步骤,传统的人工钻杆加卸方式不仅耗时费力,而且劳动强度极大,对工人的身体健康构成严重威胁。为了提高煤矿井下钻机的钻杆加卸效率,降低劳动强度,提...煤矿井下作业环境复杂多变,钻探成为煤矿开采的必备环节。钻杆加卸是钻探过程中的重要步骤,传统的人工钻杆加卸方式不仅耗时费力,而且劳动强度极大,对工人的身体健康构成严重威胁。为了提高煤矿井下钻机的钻杆加卸效率,降低劳动强度,提升作业安全性,探讨并总结当前煤矿井下智能化钻机配套钻杆自动加卸技术,发现多轴液驱机械手式换杆技术具有高度的灵活性和适应性,可作为解决多规格钻具自动加卸问题的有效方案。基于当前机械手关键技术的研究,分析得出动态路径规划方法是多轴机械手式钻杆加卸系统研究的难点,在总结当前机械手动态轨迹规划领域研究进展的基础上,分析现有路径规划方法的优缺点,特别是在动态环境下的适应性表现。在此基础上,研究了基于快速随机搜索树(Rapidly-exploring Random Tree,RRT)算法的混合轨迹规划策略在复杂环境下的应用,展示了这些方法在提升机械手路径规划精度、减少操作时间以及增强系统鲁棒性方面展现出的显著优势。针对未来研究方向,提出了进一步提升机械手动态轨迹规划算法性能,增强机械手自主作业能力,推动煤矿井下自动化技术全面应用的建议。展开更多
为研究长距离公路隧道电力电缆区在夏季机械通风条件下仍然存在的高温环境问题,以上海市G40长距离跨江隧道为研究对象,采用CFD模拟方法,探究电缆发热量、室外环境温度和通风量对电力电缆区温度场分布的影响规律,并提出适用于该隧道结构...为研究长距离公路隧道电力电缆区在夏季机械通风条件下仍然存在的高温环境问题,以上海市G40长距离跨江隧道为研究对象,采用CFD模拟方法,探究电缆发热量、室外环境温度和通风量对电力电缆区温度场分布的影响规律,并提出适用于该隧道结构的温度预测关联式,用于解决工程实践中面临的“高温区域覆盖范围如何界定”以及“下游温度超标临界条件如何判定”等关键问题。结果表明:1)在夏季机械排风工况下,电力电缆区的空气温度沿着隧道纵向呈现非线性增长趋势,表明气流驱动的热迁移现象显著;2)电缆发热量对隧道进排风温差呈现非线性增长特征,当电缆长期高负载运行时,电缆区排风温度将超过标准规定的安全阈值(≤40℃);3)降低隧道入口温度虽可减少排风温度,但会导致进排风温差扩大超出规范限值(≤10℃);4)通风量每增大87.81 m 3/s(即换气次数增大2次/h)可使排风温度降低约3.57℃,但过高的通风量会导致风机功耗激增,因此需要进一步研究通风策略以平衡降温效果与风机能耗之间的关系。展开更多
基金the National Natural Science Foundation of China(No.52204052)the NationalNatural Science Foundation of China(No.U23B20156)the Sichuan Science and Technology Program(No.2023NSFSC0933).
文摘Shale reservoirs are characterized by numerous geological discontinuities,such as bedding planes,and exhibit pronounced heterogeneity across rock layers separated by these planes.Bedding planes often possess distinct mechanical properties compared to the surrounding rock matrix,particularly in terms of damage and fracture behavior.Consequently,vertical propagation of hydraulic fractures is influenced by both bedding planes and the heterogeneity.In this study,a numerical investigation into the height growth of hydraulic fractures was conducted using the finite element method,incorporating zero-thickness cohesive elements.The analysis explored the effects of bedding planes,toughness contrasts between layers,and variations in in-situ stress across different strata.The results reveal that hydraulic fractures are more likely to propagate along bedding planes instead of traversing them and extending vertically into barrier layers when(1)bedding strength is low,(2)stress contrast between layers is high,and(3)toughness contrast is significant.Furthermore,for a given bedding strength,increased stress contrast or higher toughness contrast between layers elevate hydraulic fracture extension pressure.When a substantial stress difference exists between layers(Lc 0.4),hydraulic=fractures preferentially propagate along bedding planes.Conversely,as bedding strength increases,the propagation distance along bedding planes decreases,accompanied by an amplified horizontal compressive stress field.Notably,when the stress difference is sufficiently small(SD a phenomenon termed“stress rolling”emerges,wherein<-0.2),hydraulic fractures deviate from vertical growth and instead extend along a near-horizontal trajectory.
文摘煤矿井下作业环境复杂多变,钻探成为煤矿开采的必备环节。钻杆加卸是钻探过程中的重要步骤,传统的人工钻杆加卸方式不仅耗时费力,而且劳动强度极大,对工人的身体健康构成严重威胁。为了提高煤矿井下钻机的钻杆加卸效率,降低劳动强度,提升作业安全性,探讨并总结当前煤矿井下智能化钻机配套钻杆自动加卸技术,发现多轴液驱机械手式换杆技术具有高度的灵活性和适应性,可作为解决多规格钻具自动加卸问题的有效方案。基于当前机械手关键技术的研究,分析得出动态路径规划方法是多轴机械手式钻杆加卸系统研究的难点,在总结当前机械手动态轨迹规划领域研究进展的基础上,分析现有路径规划方法的优缺点,特别是在动态环境下的适应性表现。在此基础上,研究了基于快速随机搜索树(Rapidly-exploring Random Tree,RRT)算法的混合轨迹规划策略在复杂环境下的应用,展示了这些方法在提升机械手路径规划精度、减少操作时间以及增强系统鲁棒性方面展现出的显著优势。针对未来研究方向,提出了进一步提升机械手动态轨迹规划算法性能,增强机械手自主作业能力,推动煤矿井下自动化技术全面应用的建议。
文摘为研究长距离公路隧道电力电缆区在夏季机械通风条件下仍然存在的高温环境问题,以上海市G40长距离跨江隧道为研究对象,采用CFD模拟方法,探究电缆发热量、室外环境温度和通风量对电力电缆区温度场分布的影响规律,并提出适用于该隧道结构的温度预测关联式,用于解决工程实践中面临的“高温区域覆盖范围如何界定”以及“下游温度超标临界条件如何判定”等关键问题。结果表明:1)在夏季机械排风工况下,电力电缆区的空气温度沿着隧道纵向呈现非线性增长趋势,表明气流驱动的热迁移现象显著;2)电缆发热量对隧道进排风温差呈现非线性增长特征,当电缆长期高负载运行时,电缆区排风温度将超过标准规定的安全阈值(≤40℃);3)降低隧道入口温度虽可减少排风温度,但会导致进排风温差扩大超出规范限值(≤10℃);4)通风量每增大87.81 m 3/s(即换气次数增大2次/h)可使排风温度降低约3.57℃,但过高的通风量会导致风机功耗激增,因此需要进一步研究通风策略以平衡降温效果与风机能耗之间的关系。
