The influence of inter-band rock on rib spalling in longwall panel with large mining height

In order to improve rib stability,failure criteria and instability mode of a thick coal seam with inter-band rock layer are analysed in this study.A three-dimensional mechanical model is established for the rib by considering the rock layer.A safety factor is defined foy the rib,and it is observed that the safety factor exhibits a positive correlation with the thickness and strength of the inter-band rock.A calculation method for determining critical parameters of the rock layer is presented to ensure the rib stability.It is revealed that incomplete propagation of the fracture at the hard rock constitutes a fundamental prerequisite for ensuring the rib stability.The influence of the position of the inter-band rock in the coal seam on failure mechanism of the rib was thoroughly investigated by developing a series of physical models for the rib at the face area.The best position for the inter-band rock in the coal seam is at a height of 1.5 m away from the roof line,which tends to provide a good stability state for the rib.For different inter-band rock positions,two ways of controlling rib by increasing supports stiffness and flexible grouting reinforcement are proposed.

The height-width ratio limited value for rubber bearing isolated structure computed by uniform design method

Rubber isolation is the most mature control technology in practical application, and is widely used by short rigid buildings. However, many high isolation buildings have been built around the world in recent years, which do not follow the existing criterions and codes. Many researchers began to research the special problems caused by larger height-width ratio isolation structures. The overturning effect of high height-width ratio structures with rubber bearing is firstly studied. Considering the main factors, such as the height-width ratio of structures, type of site, the designed basic acceleration of ground motion and the decouple factor in horizon, computing experiment is defined with the Uniform Design Method, which is also known as designing isolation structure. The forces of the bearing under edge of structures based on the position of the rubber bearing are calculated. The result indicates that the rubber bearings will lose its functionality under very high tension and compressing force of earthquake motion in horizon and vertical, when the height-width ratio is over a certain value. Thus, based on the calculation result of isolation structures defined in the uniform design method, regression analysis is conducted, and also the rubber edge force regression formula are gotten, which has higher correlation and smaller standard deviation. This formula can be used to roughly calculate whether the pull force occurs at the edge of the building. By the edge bearings of isolation structure minimum force formula, the height-width ratio limited value of the isolation structure is deducted when rubber bearing has minimum force of zero.

Experimental test and theoretical calculation of the fracture height limit of gas pipe flow to Darcy flow

Low-speed flow experiments in which ultra-fine copper tubes are used to simulate micro-fractures in carbonate strata are conducted to analyze the variations of gas flow state in fractures of different fracture heights,determine flow state transition limit and transition interval,and establish the calculation method of flow state transition limit.The results show that the ideal Hagen-Poiseuille flow is the main form of gas flow in large fractures.Due to the decrease of fracture height,the gas flow in the fracture changes from Hagen-Poiseuille flow with ideal smooth seam surface to non-Hagen-Poiseuille flow,and the critical point of the transition is the boundary of flow state transition.After the fracture height continues to decrease to a certain extent below the boundary of the flow state transition fracture height,the form of gas flow gradually changes to the ideal Darcy flow,thus the transition interval of the gas flow state in the closing process of fracture can be determined.Based on the three-dimensional microconvex body scanning of the fracture surface,the material properties of fracture and properties of fluid in the fracture,a method for calculating the boundary of flow state transition is established.The experimental test and theoretical calculation show that the limit of the fracture height for the transition from pipe flow to Darcy flow is about twice the sum of the maximum height of the microconvex bodies on the upper and lower sides of the fracture.

光伏运维操作平台的设计与应用

阐述一种基于实战化技术培训的光伏运维员操作平台的设计,该操作平台通过在其支撑支架内部设置升降机构,实现高度调节功能。操作平台有延长机构、限位机构,满足光伏电站运维各类项目的实战化训练,也是相关课程实践教学设施设备的补充。

选区激光熔化成形钛合金薄壁件热行为及打印极限高度研究

为了研究钛合金薄壁件在选区激光熔化工艺下的热行为及工艺参数对打印极限高度的影响,采用理论建模、模拟仿真和正交试验法等手段开展了钛合金薄壁件在复杂热循环作用下的热行为及打印极限高度研究。分别从单层单道、单层多道和多层单道展开研究。模拟结果表明,对于单层单道成形,当激光束从节点N1移动到节点N3时,熔池峰值温度和最大冷却速率逐渐增加;对于单层多道成形,当激光束从第1道扫描至第3道时,熔池尺寸和熔池峰值温度呈递增趋势;对于多层单道成形,当激光束从第1层扫描至第5层时,熔池尺寸呈递增趋势。试验结果表明,打印极限高度与激光功率成正相关,与扫描速度呈负相关,随着扫描间距的增加先增加后减小,且与激光能量密度呈线性增长趋势。

高度受限条件下地下室抗水板加固方法研究

受连日暴雨影响,某工程地下室抗水板出现大面积开裂渗流,柱脚位置处抗水板翘起、破坏,地下承压水突涌。因建筑消防对于地下室净高的要求,无法再按原抗水板尺寸进行加固。采用在地下室防水板上钻孔排水泄压,再在原有抗水板上设置疏水层将地下水排至集水井处。此种方法增设的疏水层厚度相对较小,一方面卸除了水压,减小了荷载,保证了抗水板不再继续破坏;另一方面,有效地控制了地下水的渗流,杜绝了后续使用过程中地下室返潮、渗水等现象。

限高区域地下墙钢筋笼分节吊装技术应用

漕宝路快速路新建工程3标中春路节点为漕宝路378.2m长主线明挖段及蒲汇塘盾构接收井,横跨中春路,盾构接收井位于中春路东侧,该处为虹桥机场航道正下方,场地限高。为满足在限高下施工的要求,蒲汇塘工作井地墙钢筋笼采用分节吊装,两节钢筋笼之间采用机械连接,保障在限高下正常施工,从而保证整个漕宝路工程顺利通车。

某地铁上盖建筑采用厚板转换结构设计的研究

对南京5号线某地铁轨行区上盖建筑的转换层进行分析研究,论证了采用梁板转换体系、厚板转换体系的可行性,并对比分析了两种建模方式对转换厚板内力及配筋的影响。研究结果表明:在转换层高度受限的情况下,厚板转换体系可行,两种厚板转换计算模型计算结果真实可靠,设计时采用两种模型计算结果的包络值。

梁高受限空心板桥横向连接优化设计分析

以某梁高受限的空心板漫水桥加固工程为例,通过建立有限元实体模型,详细分析了旧桥空心板梁及铰缝的受力状态,结果显示原空心板间的铰缝截面小且受力复杂,在重载作用下易破坏且影响结构横向传力,原桥设计荷载低且配筋弱,在荷载和环境作用下出现大量病害。为彻底解决桥梁结构病害,对下部结构进行加固后更换了上部结构,在梁高受限条件下设计了一种横向湿接的预应力空心板梁。经对比分析可知,新空心板梁优化了横向连接,改善了接缝横向受力状态,提高了结构整体性、承载能力和耐久性,并且加快了施工速度,减少了河道占用,目前改造后的桥梁使用状态良好,该设计思路及加固方案可为类似工程提供借鉴。

一种驱动电机用矩形橡胶密封系统的设计方法

本文以矩形橡胶密封圈和矩形密封槽的匹配设计作为研究对象,根据压缩率和填充率的范围要求,对矩形橡胶密封圈和密封槽尺寸进行匹配设计。同时,对于该密封系统在新能源汽车驱动电机环境的实际应用,在不同的环境温度时,对于不同的尺寸匹配结果,基于Ansys软件进行了热仿真,根据仿真结果发现,当环境温度在-40℃~160℃区间变化时,不同尺寸匹配情况下的压缩率和填充率都是随环境温度的升高而升高,但是依然满足密封系统的压缩率和填充率的范围要求。文章提出的根据压缩率和填充率范围要求,在温度变化的环境下,对矩形橡胶密封圈和矩形密封槽进行匹配设计,具有一定的工程指导意义。

Limitation of fault-sealing and its control on hydrocarbon accumulation——An example from the Laoyemiao Oilfi eld of the Nanpu Sag

Based on previous studies on the internal structures of fault belts, the fault belts in the Laoyemiao Oilfield of the Nanpu Sag can be divided into three units, a crushed zone, an upper induced fracture zone and a lower induced fracture zone according to the log response characteristics. The upper induced fracture zone is characterized by the development of pervasive fractures and has a poor sealing or non-sealing capability. It therefore can act as pathways for hydrocarbon migration. The lower induced fracture zone consists of fewer fractures and has limited sealing capability. The crushed zone has a good sealing capability comparable to mudstone and can thus prevent lateral migration of fluid. Through physical modeling and comparing laboratory data with calculated data of oil column heights of traps sealed by faults, it is concluded that the fault-sealing capability for oil and gas is limited. When the oil column height reaches a threshold, oil will spill over from the top of reservoir along the lower induced fracture zone under the action of buoyancy, and the size of reservoir will remain unchanged. Analysis of the formation mechanisms of the fault-sealed reservoirs in the Nanpu Sag indicated that the charging sequence of oil and gas in the reservoir was from lower formation to upper formation, with the fault playing an important role in oil and gas accumulation. The hydrocarbon potential in reverse fault-sealed traps is much better than that in the consequent fault-sealed traps. The reverse fault-sealed traps are favorable and preferred exploration targets.

一种基于弹性理论的大采高区段煤柱合理尺寸计算方法

不同工况下区段煤柱两侧支承压力分布及岩体变形存在显著差异,考虑煤柱两侧不同支承压力对煤柱整体稳定性的影响,基于大采高区段煤柱的弹性力学计算模型,分析了支承压力下煤柱任一单元岩体的应力应变分量。通过建立大采高煤柱弹塑性界面上岩体的柱条模型,确定在0.65倍煤柱高度处单元岩体将首先发生水平拉伸破坏,利用虎克定律提出了该单元岩体极限拉应变与煤柱极限平衡区宽度的关系式。依据煤柱破裂区岩体的受力特征,运用摩尔库伦准则推导了煤柱破裂区宽度的计算公式。结果表明:①煤柱极限平衡区宽度与岩体极限拉应变和弹性模量反相关,与煤柱埋深和煤柱高度正相关;②煤柱高度及其与顶底板的界面摩擦角是影响破裂区宽度的关键性因素;③煤柱两侧不同工况下,煤柱岩体极限拉应变与其所受侧压呈正变关系,区段煤柱采空区侧所受侧压较巷道侧偏大,采空区侧岩体的极限拉应变也相应较大,表现为采空侧极限平衡区宽度较巷道侧偏小。最后,将上述理论公式应用于陕北某矿30109工作面大采高区段煤柱极限平衡区和破裂区宽度的分析计算,给出了该工作面两侧区段煤柱的合理宽度及其支护方案。工程应用表明,30109工作面区段巷道围岩变形控制效果良好,满足现场生产需求。

The Upper Limit Size of Reservoir-Induced Earthquakes

We showed the relation between the magnitude of induced earthquake and the reservoir storage and dam height based on the global catalog from 1967 to 1989 compiled by Ding Yuanzhang(1989).By multiplying reservoir storage with dam height,we introduced a new parameter named E_E.We found that the cases with specific E_E and magnitude do not exceed a limit.Based on the discussion of its physics,we called E_E the equivalent energy.We considered this limit as the upper limit of magnitude for reservoir-induced earthquakes.The result was proved by the recent cases occurring in China.This size limitation can be used as a helpful consideration for reservoir design.

黏土地基上海洋平台桩靴峰值阻力上限分析

在自升式平台的预压载过程中,桩靴在层状地基上较易发生“穿刺”现象,很大程度上影响着平台的安全运行。准确地分析桩靴峰值阻力,避免平台桩靴发生“穿刺”是非常重要的。采用极限分析上限定理,合理构建运动许可速度场,从理论上推导了层状地基上桩靴峰值阻力的上限解答。为了进一步验证峰值阻力理论解答的准确性,采用ABAQUS有限元软件构建了“桩靴—弹塑性海床”的三维数值模型,对桩靴贯入海床的过程进行了数值模拟,分析桩靴周围土体的塑性变形演变规律,研究土体的破坏机理。研究结果表明:推导的桩靴峰值阻力上限解答,能够较好地计算层状地基极限承载能力,通过与离心机试验和数值结果对比,计算误差在18%以内;给出的运动许可速度场能够较好地反映桩靴周围土体破坏模式;桩靴阻力达到峰值时,下层软土中的土塞高度约为桩靴直径的0.2倍。

新鲜完整花岗岩陡崖极限高度理论计算结果探讨

作为坚硬完整而各向同性的代表性岩石,新鲜花岗岩以其陡峻的山势构成自然界独特的、高度不等的陡崖等地貌景观。陡崖的稳定性与其高度密切相关,使得极限高度的数值对地质遗迹保护和自然景观开发具有重要意义,但对其理论研究鲜有报道。采用数学统计、破坏判据、极限平衡等方法开展研究。首先对收集自文献和报告中118组花岗岩物理力学参数值做频数统计,得到其中值密度ρ=2.61 g/cm^(3),泊松比μ=0.20,内摩擦角ψ=42.1°,内聚力C=28.15 MPa,抗压强度Rc=150 MPa,抗拉强度Rt=10 MPa。然后从莫尔-库伦强度准则等不同理论公式出发,推求其直立陡崖(坡角90°)极限高度为1532.57~5747.13 m。如采用斜坡刚体极限平衡法计算,则受到软弱结构面影响的极限高度为300 m。据国内外花岗岩陡崖实际数据,发现同时考虑拉破坏和剪破坏的卡尔曼法和莫尔-库伦强度准则的计算结果较为可信,所得极限高度为1500~2500 m。最后利用有限元软件Ansys平面应变计算,结果表明2500 m理论极限高度结论可信性。本文最后讨论了研究中未考虑的结构面控制及外动力地质作用影响,说明自然界中难以发现上述极限高度的几方面影响因素,从而为更全面认识新鲜完整花岗岩陡崖高度变化及稳定性评价提供依据。

双目视觉感知下的公路限高实时预警算法

针对车辆运动工况下对种类繁杂的公路限高设施测高难的问题,提出一种双目相机限高目标实时监测算法。通过分析限高场景及设施,采集并构建大规模多场景的公路限高数据集;采用基于深度学习的检测和跟踪算法获取目标区域;利用多步多尺度的滤波算法对双目视差数据进行处理,得到高置信度的限高设施视差数据,进而计算距离及高度信息;最后采用鲁棒性输出策略对计算得到的测距和测高数据进行输出预警。通过多场景限高测试,目标检测精度为98.77%、漏检率为0.87%、误检率为0.36%,在60 m内的平均测高误差小于4%。实验结果表明该算法可以实现公路限高目标的自动检测,能够实时鲁棒地输出测距、测高和预警信息。

板材翻边试验装置开发与性能研究

利用自主设计研发的模具结构对高强钢材料进行典型参数下的两种翻边试验,得到高强钢在实际工程环境下的翻边极限高度。对比不同钢种、厚度、翻边工艺和切边状态下的材料翻边性能,研究板材翻边极限高度的变化规律与影响因素。结果表明:随着钢种强度的升高、延伸率的降低,翻边极限高度呈下降趋势;对于同一强度级别的低合金钢的翻边能力要比双相钢强;同种材料的翻边高度随板厚的增加而增加;同种材质同样厚度下V形翻边高度高于直角翻边;利用剪板机剪切得到的样件翻边高度要低于激光切割。

地基条件对仰斜式挡墙地震响应影响及墙高限值研究

地基条件和墙高是影响挡土墙地震响应特征的重要因素。建立不同地基条件的仰斜式挡土墙有限元时程分析模型,以墙身外倾最大危险状态为最不利时刻,研究地基条件和墙高对挡墙动力响应及墙-土相互作用的影响特征,并以满足力学检算和墙身位移限值为出发点,提出同时考虑地基条件和地震峰值加速度PGA的仰斜式挡墙墙高控制建议。结果表明:岩质地基挡墙墙背动土压力沿墙高呈中部大、上下小的凸形分布,大震下土压力较中震时有小幅减小;基底反力呈墙踵为0、墙趾集中的三角形图式,且随PGA和墙高的增加踵部脱空趋势更为明显;土质地基挡墙因墙底地基土变形对墙后填土的牵连作用,填土跟随墙身运动的趋势加剧,墙背动土压力与PGA呈正相关并沿墙高近似呈线性分布,于墙底处最大;墙身往复摆动使踵趾端地基土体塑性变形较基底中部明显,基底反力峰值向中部转移;根据最不利时刻稳定性、承载力检算,考虑对墙身位移合理限制,提出地震区仰斜式挡墙的允许墙高在设防PGA不超过0.2g时为8 m, 0.4g大震下硬质岩地基挡墙可达8 m,软质岩地基挡墙不宜超过6 m,碎石土、砂质黏土地基挡墙不宜超过4 m。

坡高及坡比对渠道边坡可靠度的影响

【目的】探讨坡高和坡比对渠道边坡可靠度的影响,为渠道边坡的优化设计提供科学依据。【方法】利用Karhunen-Loève(K-L)展开法建立土体参数的二维随机场模型,使用简化的Bishop法计算渠道边坡的安全系数,通过Monte Carlo模拟渠道边坡的失效概率和可靠度指标,分析坡高和坡比对渠道边坡可靠度的影响。【结果】不考虑和考虑土体参数的空间变异性时,可靠度指标均随坡比的增大而减小;不考虑土体参数的空间变异性时,可靠度指标随坡高的增大而逐渐减小,但在粘聚力变异系数较大而内摩擦角变异系数较小时,可靠度指标呈现随坡高增大而增大的特殊现象;考虑土体参数的空间变异性时,在粘聚力变异性较小而内摩擦角变异性较大时,可靠度指标随坡高的增大而减小,其他情况均呈现随坡高的增大而增大的特殊现象。【结论】相对于降低坡高而言,采取减小坡比的措施可以更好地保障边坡可靠度,降低渠道边坡工程风险。

面向净空保护的高层建筑对雷达电磁干扰分析

针对净空保护需求,在建设高层建筑时,其高度必须低于航空限高,在不侵入航空器飞行高度同时其对航空器与机场之间的电磁波产生一些干扰。机场雷达在监测航空器的同时,可能会接受到高层建筑导致的航空器镜像电磁波,即雷达监测到航空器虚影。在求解这样的电大尺寸问题,因其计算量与内存需求大,本文应用了弹跳射线法进行计算,参考分析某市关于建设高层建筑对于当地机场的电磁干扰影响,并建立了虚影概率模型。