Mode of overlying rock roofing structure in large mining height coal face and analysis of support resistance

The mining space of large mining height coal face is large,the range of movement and caving of rock strata is large and the stability of supports at coal face is low and damage rate of supports is high,which significantly affects the safe and efficient production of coal mines.By similar simulation experiment and theoretical analysis,the mode of fractured roofing structure of large mining height coal face and the method of determination of reasonable support resistance of the support was evaluated.Analysis shows that the structural mode of "combined cantilever beam – non-hinged roofing – hinged roofing" of the large mining height coal face appears at the roofing of large mining height coal face.The supporting factor of caved gangue at the gob is introduced,the calculating equations of the fractured step distance of roofing were derived and conventional calculating method of caved height of roofing was corrected and the method of determination of the length and height of each structural area of the roofing was provided.With reference to the excavating conditions at Jinhuagong coal mine in Datong minefield,the dimensions of structural areas of the roofing of the coal face were determined and analyzed,and reasonable support resistance of the height coal face was acquired.By selecting Model ZZ13000/28/60 support and with procedures of advanced pre-cracking blasting,the safe production of large mining height coal face was assured.

Similar material simulation research on movement law of roof over-lying strata in stope of fully mechanized caving face with large mining height

Similar material simulation test W9-15 101 fully mechanized caving face with was carried out in a geological model of large mining height in the Liuhuanggou Colliery, in Xinjiang Uigur Autonomous Region. The roof overlying strata movement law in the stope of a fully mechanized caving face with large mining height was studied and show that the roof overlying strata in the stope of a fully mechanized caving face with large mining height can be formed into a stable arch structure; the fracture rock beam is formed resembling a ＂bond beam＂, but it has essentially the structure of ＂multi-span beams＂ under the big structure of the stable arch. The roof overlying strata movement law in the stope of a fully mechanized caving face with large mining height is similar to that of the common, fully mechanized caving stope, which is determined by the deformation and instability of the structure of ＂multi-span beams＂. But because of the differences between the mining heights, the peak pressure in the stope of a fully mechanized caving face with large mining height is smaller while the affected area of abutment pressure is wider in the front of the working face; this is the obvious difference in abutment pressure between the stope of a fully mechanized caving face with large mining height and that of the common.

Mechanism and practice of rock control in deep large span cut holes

Deep large span cut holes are difficult to stabilize. The 7801 cut hole in the Lu'an Wuyang Mine was used as this project's background. The main factors affecting large span cut hole stability are analyzed. Pre- stressed bolting theory was used to design a roof control method for a large span roadway. By reducing the span and applying equal strength coordinated supports the rock could be stabilized. The control prin- ciples and methods are given herein along with the analysis. A double micro arch cross section roadway is defined and its use in solving the current problem is described. Beam arch theory was used to build a model of the double micro arch cross section roadway. A support reverse force model for the arch foot intersection was also derived. A support method based upon reducing the width of the large span in the cut hole is presented. These results show that the reduced span of the roadway roof plus the use of cable anchors and single supports gives an effective way to control the large span cut hole. On site monitoring showed that the reduced span support from the double micro arch cross section roadway design had a significant effect. The roadway surface displacement was small and harmful deformation of the cut hole was effectively controlled. This will ensure its long term stability.

Bolt Supporting of Large-Span Soft Rock Roadway in Shaqu Colliery

The instability of trapezoidal Ⅰ-steel support is analysed for the compound roof of main coal seam in Shaqu Colliery, and the mechanism of bolt supporting is studied. A scheme of bolt supporting has been given and put into practice, remarkable technical and economic benefits have been got.

Ground pressure law of fully mechanized large cutting height face in extremely-soft thick seam and stability control in tip-to-face area

When stepped coal getting technology was applied to high seam mining working face, with field observations the following aspects of working face were analyzed based on the inherent conditions of extremely soft thick seam mined by Liangbei Mine, such as the brokenness and activity law of rock seam in the working face, the law of load-bearing of its supports, and the instability character of coal or rock in tip-to-face area. The following are the major laws. Pressure intensity of roof in high seam mining with extremely soft thick seam is stronger than one in slicing and sublevel-caving as a whole. But the greater crushing deformation of coal side makes pressure intensity of roof in the middle of working face be equivalent to one in sublevel-caving. In the middle of working face the roof brokenness has less dynamic load effect than roof brokenness in the two ends of working face. The brokenness instability of distinct pace of roof brings several load-bearings to supports. In condition of extremely soft thick seam, the ratio of resistance increment of supports in two ends of working face is obviously greater than that of supports in the middle. Most sloughing in coal side is triangular slop sloughing caused by shear slipping in high seam mining with extremely soft thick seam. Ultrahigh mining is the major reason for roof fall. Instability of coal or rock in tip-to-face area can be controlled effectively with the methods such as improving setting load of supports, mining along roof by reinforcing floor and protecting the immediate roof in time, and so on.

水滴形大跨钢屋盖结构风洞试验和风振分析

自然风经过大跨结构时,由于结构屋顶形状不规则,通常会引起柔性屋面的振动,因此针对大跨屋面结构抗风设计需要考虑风压分布和风振响应。以陕西省水务集团矿泉水生产车间为工程背景,制作了1∶200的刚性模型,通过刚性模型风洞试验测得该水滴型大跨钢屋盖结构的表面风压,研究了屋盖表面典型测点及整体的风压分布规律。基于风洞试验数据,对结构进行风振时程分析,得到了屋盖表面的风振响应和风振系数。结合刚性模型风洞试验和风振分析,深入研究了水滴形大跨屋盖结构的风压分布规律和风致振动特性,并总结了其共性规律。

屋面花架大跨度悬挑梁板支撑架施工技术

研究了屋面花架大跨度悬挑梁板支撑架施工技术,在明确工程概况的基础上,分析了大跨度悬挑梁板支撑架施工工艺流程,强调了受力计算的重要性,并针对预留压环、“工”字钢装拆、脚手架安装、混凝土浇筑、脚手架拆除等关键环节的技术要点优化施工方案,提高施工技术应用的科学性、合理性及可靠性。

襄阳东站钢屋盖超多杆连接节点设计与足尺模型试验研究

襄阳东站屋盖南北向长358m,东西向最大跨度86m,采用焊接球钢网架,整体不设变形缝,南端开设瀑布造型大洞口,由于屋盖结构超长、不连续、大悬挑及瀑布造型使得钢屋盖空间受力十分复杂,特在分叉柱柱顶沿南北向设置加强杆以加强屋盖瀑布区洞口两侧边缘约束刚度及改善结构整体受力性能。钢屋盖瀑布区悬挑端分叉柱柱顶节点相连杆件达12根之多,该节点作为屋盖结构的关键节点,其受力状态尤为复杂,创新地采用了半铸造半相贯焊连接形式并采取了构造加强措施,针对该超多杆连接节点进行了足尺模型加载试验验证,详细介绍了试验加载装置、加载方案、试验现象及试验结果,并进行了有限元对比分析。结果表明有限元对比分析结果与加载试验吻合较好;该超多杆半铸造半相贯焊连接节点构造合理、承载力高,薄弱部位出现在与铸造本体相连的接长钢管上,满足强节点弱构件、强连接弱构件的设计要求。

榆神矿区多层厚硬顶板强矿压显现及覆岩破断运动规律研究

针对榆神矿区多层厚硬顶板条件下工作面强矿压和邻空侧巷道变形严重问题,综合采用理论分析、数值计算和微震监测方法,分析了多关键层结构下顶板覆岩破断和邻空侧巷道围岩应力特征。研究结果表明:多层厚硬岩层条件下,顶板破断垂向位移和能量均呈现明显的“低、中、高”分区特征,中高位岩层破断明显滞后于低位岩层,这构成了工作面“大、小周期”的重要结构基础;本工作面开采时,相邻采空区破碎顶板大能量微震事件增多、破断强度较高,并可对邻空回风巷围岩形成强二次采动影响,这是邻空侧回风巷高应力、强变形的主要诱因。同时,高低位多关键层组合破断可导致“大周期”来压发生强度和风险上升,对关键层顶板破断运动规律进行控制是降低“大周期”强度和频率的有效途径之一。

瓯海奥体中心体育馆100m跨无环索弦支网壳结构设计

瓯海奥体中心由体育场、体育馆、游泳馆及体育配套用房组成,其中体育馆主体结构采用钢筋混凝土框架结构,屋盖采用了无环索弦支网壳结构体系,为国内外首例该结构体系工程。设计中针对屋盖结构进行了屈曲分析及抗连续倒塌分析,结果表明结构的整体稳定性较好、抗连续倒塌能力强,进一步证明了结构体系选择的合理性。对拉索索力进行了专项分析,保证在各工况组合下拉索均不破断及退出受拉状态,且刚度退化后仍满足设计要求。

大跨度破碎岩体顶板预应力锚固支护机理及效果研究

大跨度破碎岩体顶板采用预应力锚固支护,能最大程度地维持顶板围岩稳定,因此研究预应力锚固对大跨度破碎岩体顶板的支护机理及支护效果,对于保障破碎岩体下大跨度地下工程、露天大断面隧道工程的长期稳定性具有重要意义。对锚固后锚固体强度变化进行力学解析,剖析大跨度破碎岩体顶板预应力锚固支护机理,以云南金厂河多金属矿Ⅳ级破碎岩体大跨度顶板支护难题为工程背景,针对其支护方式建立数值模型进行分析,对FLAC3D软件中结构单元Cable的布置,设计新的三段式布置法,将预应力锚杆(索)在FLAC3D软件层面分为预紧段、自由段、锚固段分别赋予指定参数进行数值计算,建立3组不同支护方式的数值模拟方案对预应力锚固支护效果进行验证。结果表明:预应力锚固后,支护区域顶板受拉应力基本小于破碎岩体顶板抗拉强度,塑性区体积对比普通无预应力支护方案,下降比率达到61.95%,顶板Z方向垂直沉降量降低比率高达83.90%,预应力锚固范围内围岩得到了有效控制。

广州南沙国际金融论坛永久会址主体结构设计

广州南沙国际金融论坛永久会址属于大型复杂会议类建筑,具有大底盘双塔、钢屋盖连体、大开洞、竖向质心偏移、大跨结构等多项不规则项。介绍了结构重力体系和抗侧体系的选型思路,主体结构选用混凝土框架+屈曲约束支撑体系,外表皮采用空间钢结构。重点分析了单塔与整体结构的差异以及钢屋盖对下部双塔的影响。通过弹塑性分析,对大震作用下各个时程点的损伤水平进行评估,对大开洞的楼板进行了地震及温度作用下的楼板应力分析;对大跨桁架进行了抗连续倒塌分析。结果表明结构可满足大震不倒的要求,支撑承载力能充分发挥,大底盘结构具有良好的基座支撑特性。

沿海地区索结构体育馆风洞试验与群风效应研究

针对两类屋面型式(上凸型和下凹型)、四种屋盖结构(单层马鞍形索网、轮辐式双层索网、索穹顶、弦支穹顶),设计制作了缩尺比分别为1∶250、1∶200两个试验模型,在B类地貌下开展了60组模型风洞试验,探究了全风向角下两类屋盖结构的风压峰值分布规律,分析了不同风向角、邻近建筑对目标建筑物风压特性的影响规律。结果表明:全风向角下来流方向无邻近建筑影响时,两类屋盖迎风面区域的负风压峰值最大,分别较上凸型和下凹型屋盖中间区域的负风压峰值高约3.0、1.5倍;屋盖中间区域风压峰值分布均匀,以承载负风压为主,仅下凹型屋盖中部出现正风压;风向角对屋盖风压分布的影响主要体现邻近建筑物的干扰上,其对屋盖平均和脉动风压系数的影响以来流方向无邻近建筑时最大、来流方向有邻近建筑时次之、尾流方向有邻近建筑物时最小;屋盖迎风面测点风压概率分布具有明显的非高斯特征,存在极大负压值,而屋盖中间和尾流区域的测点风压具有典型的正态分布特征。

基于改进K-means算法的大跨屋盖结构表面风荷载分区研究

针对K-means算法进行大跨屋盖结构表面风荷载分区中存在的分类数k值需凭经验事先给定以及所有初始聚类中心均需随机选取带来的分类情况数过多、从中寻找最优分类结果工作量大且效率低的问题,提出基于改进K-means算法的大跨屋盖结构表面风荷载分区方法。首先,建立分类数k与其相应测点风荷载的误差平方和(Sum of the Squared Errors:SSE)关系曲线,引入手肘法基本思想,实现最优分类数kst值的精准识别;其次,在首个初始聚类中心随机选取基础上,引入轮盘法基本思想,完成对剩余初始聚类中心的高效选取;然后,根据类内紧凑、类间分散的原则,通过类内紧凑性判定指标S(k)和类间分散性判定指标D(k),构造并借助SD(k)值有效性检验,得到最优的风荷载分区结果;最后,以北京奥林匹克网球中心大跨悬挑屋盖结构为例,针对风洞试验所得风荷载测试结果,采用所提方法对其表面最不利风压系数进行分区计算,并与传统K-means算法进行对比,结果表明,所提方法能够高效实现大跨屋盖结构表面风压分区计算,具有较好的工程应用价值。

梁北矿松软大采高工作面高水充填沿空留巷技术研究

以高水材料适应性研究为基础,通过分析梁北煤矿厚硬顶板大采高工作面沿空留巷围岩控制难点,提出“预裂切顶-高水充填-超前加固”沿空留巷技术。通过室内试验确定了高水充填材料最佳水灰比、早强剂掺量和用水温度;采用理论分析和工程类比确定了预裂切顶、超前加固和高水充填支护方案;采用数值模拟分析了沿空留巷方案的可行性。工程实践效果表明,围岩变形滞后工作面100~150 m趋于稳定,变形整体可控,留巷效果较好。

厚煤层大采高综采面顶板破断规律及机理研究

以杭来湾煤矿首个大采高30201工作面为例,通过数值模拟、理论分析和现场实测的方法,分别对工作面开采过程中顶板破断规律进行研究。基本顶以“悬臂梁”、“砌体梁”的结构形式周期发生破断,造成工作面大、小周期来压显现。建立了工作面顶板力学模型,给出来压步距的计算方法。现场实测表明最大步距67.6 m是平均步距34.4 m的1.97倍,说明约2次小周期来压才有1次大周期来压。

钢筋混凝土仿古建筑双曲屋面施工工艺研究

探讨在钢筋混凝土仿古建筑双曲屋面施工的工艺和技术要点,以及在“盘扣-木模”支撑体系下实现复杂结构的施工过程。以某项目斋堂综合楼屋面为例,介绍大跨度组合曲面结构的施工难点,包括曲面造型、高低跨屋面和大跨度预应力曲屋面。通过对深化BIM模型、模板支撑架定位、曲面模板拼装、钢筋绑扎、混凝土浇筑以及过程控制及养护等关键工艺的突破,成功实现在“盘扣-木模”支撑体系下的双曲屋面施工。总结高低跨屋面施工的关键工序和大跨度预应力曲屋面的特殊处理方法,以期为类似工程提供经验。

乌鲁木齐机场T4航站楼双曲面金属屋面工程设计

乌鲁木齐机场T4航站楼为双曲造型的金属屋面,在实现建筑美学追求的同时,也给工程在设计与安装施工上带来诸多挑战。本文重点介绍了该项目的金属屋面系统、天沟系统、采光天窗系统、檐口蜂窝铝板系统和室外吊顶系统的设计要点、安装施工难点及采用的创新性解决方案。

南京某文娱中心大跨空间钢结构设计

南京某文娱中心为造型复杂的大跨空间钢结构体系,由异型屋面、超高排架柱和高大抗风幕墙构成。为满足屋面建筑造型和屋顶排烟等需求,提出了双向变高度的折板网架屋盖结构形式,最大限度降低了二次找坡的用钢量。基于可视化编程平台Grasshopper,通过分区处理的方式实现了屋盖的参数化建模,后导入3D3S进行结构分析和设计,结果表明该屋盖整体刚度较好,满足设计要求。屋盖下方采用25根无侧向支撑的超高排架柱提供支承,针对柱高10~60m的情况,对比了混凝土柱、四肢钢管格构柱、四肢钢管混凝土格构柱在截面、成本和功能等角度的差异,最终确定采用经济性和功能均较好的四肢钢管格构柱。根据不同区域特点,将抗风幕墙分为落地幕墙和吊挂幕墙,探讨了它们与主体结构的连接方式,并针对落地幕墙进行了平面桁架、立体桁架和实腹箱形柱3种幕墙结构方案的比选,最终采用成本最低的平面桁架方案。

某博物馆大跨钢空腹夹层板屋盖设计

以湖北省天门市某博物馆的大跨度钢空腹夹层板楼盖为实例设计,介绍了钢空腹夹层板的设计方法和结构布置,基于YJK模型和SAP2000模型分析了实用计算方法和壳单元有限元模型计算结果的变形和受力的差异及其原因,对比研究了传统方管剪力键和新型十字剪力键在空腹夹层板结构中的受力表现。结果表明,本工程中实用方法与壳单元有限元模型计算得到的挠度结果吻合性较好,实用方法难以考虑次弯矩,会导致受压板件的计算应力较壳单元有限元模型明显偏小;剪力键的构造对结构受力有一定影响,新型十字剪力键连接的弦杆应力较方管剪力键略小,应力集中情况在一定条件下更缓和;通过增加部分加劲肋板,可以减小支座端应力。