High prestress truss cable support principle and its application in large cross section coal roadway

With the enlarge of cross section of roadway, the radius of plastic area and broken area increase, and the tensile stress and shear stress distributing in roof coal-rock layers relevantly increase, which induce support effect not obvious for ordinary bolt（cable）. While bounding point and support structure of the truss cable is in vertex angle of roadway, and supplies coal-rock layers in bounding area with the horizontal and vertical pressure, so it settles the support problems in large cross section coal roadway. From the point of view of mechanics, gave emphasis on the invalid mechanics of ordinary bolt （cable） in large cross section coal roadway and supported mechanics of prestress truss cable. The author successfully used this technique in Wuyang Mine, and had the huge economic efficiency and the social benefit.

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.

Simulation of the RCS Range Resolution of Extremely Large Target

The high frequency hybrid technique based on an iterative Physical Optics(PC)) and the method of equivalent current (MEC) approach is developed for predicting rangeresolution of the Radar Cross Section (RCS) in the spatial domain. We introduce the hybrid highfrequency method to simulate range resolution of the extremely large target in the near zone. Thispaper applies this method to simulate the range resolution of the two 1 m X 1 m plates and the ship.The study improves the speed of simulatingthe range resolution of the extremely large target and isprepared for the application of the extrapolation and interpolation in the spatial domain.

Dynamic plastic response of clamped stiffened plates with large deflection

Study on the dynamic response, and especially the nonlinear dynamic response of stiffened plates is complicated by their discontinuity and inhomogeneity. The finite element method (FEM) and the finite strip method are usually adopted in their analysis. Although many useful conclusions have been obtained, the computational cost is enormous. Based on some assumptions, the dynamic plastic response of clamped stiffened plates with large deflections was theoretically investigated herein by a singly symmetric beam model. Firstly, the deflection conditions that a plastic string must satisfy were obtained by the linearized moment-axial force interaction curve for singly symmetric cross sections and the associated plastic flow rule. Secondly, the possible motion mechanisms of the beam under different load intensity were analysed in detail. For structures with plastic deformations, a simplified method was then given that the arbitrary impact load can be replaced equivalently by a rectangular pulse. Finally, to confirm the validity of the proposed method, the dynamic plastic response of a one-way stiffened plate with four fully clamped edges was calculated. The theoretical results were in good agreement with those of FEM. It indicates that the present calculation model is easy and feasible, and the equivalent substitution of load almost has no influence on the final deflection.

Treat-to-target in Crohn's disease:Will transmural healing become a therapeutic endpoint?

Crohn's disease(CD) represents a chronic transmural inflammatory condition of the gastrointestinal tract, which usually leads to structural damage and signific-ant disability. Deep remission--defined by both clinical and endoscopic remission, signifying mucosal healing-represents the current endpoint in the treat--to--target strategy, significantly improving patients' long--term outcomes. Transmural healing(TH) could be a more effe-ctive target, but this possibility remains unclear. This narrative review aims to critically review and summarize the available literature relating TH to long--term outcomes, being the first of its kind and to the best of the author's knowledge. A systematic literature search(from incep-tion to March 31 2018) was performed, using multiple databases, and identifying seven full--text manuscripts. In those studies, long--term favorable outcomes(≥ 52 wk) included sustained clinical remission, as well as fewer therapeutic changes, CD--related hospitalizations, and surgeries. Despite heterogeneous design and me-thodological limitations, six of the studies demonstrated that TH or intestinal healing(TH plus mucosal healing) were predictive for the aforementioned favorable out-comes. Therefore, TH may become a reasonable the-rapeutic target and be included in the concept of deep remission. Further prospective, well-designed, multicenter trials aiming to better define the role of TH in personalized therapy for CD and to determine the long-term influence of TH on bowel damage and disability are warranted.

A defect recognition model for cross-section profile of hot-rolled strip based on deep learning

The cross-section profile is a key signal for evaluating hot-rolled strip quality,and ignoring its defects can easily lead to a final failure.The characteristics of complex curve,significant irregular fluctuation and imperfect sample data make it a challenge of recognizing cross-section defects,and current industrial judgment methods rely excessively on human decision making.A novel stacked denoising autoencoders(SDAE)model optimized with support vector machine(SVM)theory was proposed for the recognition of cross-section defects.Firstly,interpolation filtering and principal component analysis were employed to linearly reduce the data dimensionality of the profile curve.Secondly,the deep learning algorithm SDAE was used layer by layer for greedy unsupervised feature learning,and its final layer of back-propagation neural network was replaced by SVM for supervised learning of the final features,and the final model SDAE_SVM was obtained by further optimizing the entire network parameters via error back-propagation.Finally,the curve mirroring and combination stitching methods were used as data augmentation for the training set,which dealt with the problem of sample imbalance in the original data set,and the accuracy of cross-section defect prediction was further improved.The approach was applied in a 1780-mm hot rolling line of a steel mill to achieve the automatic diagnosis and classification of defects in cross-section profile of hot-rolled strip,which helps to reduce flatness quality concerns in downstream processes.

新景矿大断面岩巷综掘技术研究与应用

为提高掘进速度,保证巷道稳定,在新景矿15号煤采区集中辅助运输巷开展了大断面岩巷综合机械化掘进技术的研究。在分析当前施工工艺以及支护中存在问题的基础上,提出了以EBZ320D掘进机和CMM2-25型锚杆钻机为主要设备的综合机械化岩巷掘进作业线。理论分析了锚杆索围岩强度强化理论,结合现场实际情况,设计了以不同长度锚索为主的支护方式。现场应用表明,应用新的综合机械化掘进技术后,巷道变形量小,掘进速度快,施工成本低,经济社会效益显著,应用效果良好。

乌兰木伦煤矿大断面硐室围岩变形破坏规律及控制

针对煤矿井下巷道大断面硐室的围岩变形破坏问题,以乌兰木伦煤矿井下分选及充填大断面硐室为研究对象,采用相似模拟实验方法,进行单调递增加载和恒定荷载加载单轴压缩实验,对大断面硐室围岩变形破坏规律进行了研究。结果表明:①2种加载方式在压密阶段、弹性变形阶段及微破裂稳定发展阶段破坏演化和变形位移趋势相似。②采用单调递增加载方式的试样裂纹较少但裂纹缝隙较大,试样沿着主裂纹突然发生破断,期间有大量碎屑飞出,试样变形位置主要集中在围岩边界,破坏时释放能量较多,但峰后释放能量持续时间较短。③采用恒定荷载加载方式的试样应力保持不变,应变缓慢增加,期间产生大量微小裂纹,试样变形位置主要围绕在硐室周围,破坏时释放能量较少,但峰后释放能量持续时间较长。依据大断面硐室围岩变形破坏规律,提出了锚杆索支护方案:硐室顶部打长锚索,将顶板和上方坚硬岩石连成整体;在硐室煤岩交界处打倾斜锚杆,将煤岩交界面与周围岩体紧密连接。数值模拟结果表明,支护后围岩应力、位移、塑性区均明显减小,围岩稳定性大幅提高,支护效果良好。

大悬挑弧形变截面组合梁楼盖施工过程分析

中关村论坛永久会址主会场东入口应用了大悬挑弧形变截面组合梁楼盖,通过采用FEA–NX软件,对拟定的施工方案进行了有限元分析,对比分析不同方案的结构内力和变形规律,其可为施工方案的制订提供理论支撑。

凤凰山特大断面黄土隧道五步单侧壁导坑法研究

为解决特大断面黄土隧道采用双侧壁导坑法施工进度慢、成本高的问题,以G30连霍高速公路清水驿至忠和段扩容改造工程凤凰山隧道为背景,提出五步单侧壁导坑法。通过数值模拟对比分析双侧壁导坑法、五步单侧壁导坑法、传统单侧壁导坑法和台阶法在施工过程中的围岩变形及钢拱架应力,并结合现场试验段监测数据验证特大断面凤凰山隧道采用五步单侧壁导坑法施工的可行性。结果表明:1)五步单侧壁导坑法拱顶沉降和水平收敛比传统单侧壁导坑法分别减小3.59 cm和1.31 cm,比双侧壁导坑法分别增大1.4 cm和0.59 cm;钢拱架应力除拱肩外均小于双侧壁导坑法,最大处减少了70 MPa,钢拱架应力最大值与钢材屈服强度的比值比双侧壁导坑法增大0.04,比单侧壁导坑法减小0.08。2)传统单侧壁导坑法的安全性小于五步单侧壁导坑法,改进后的五步单侧壁导坑法相比双侧壁导坑法能在控制围岩变形的同时加快施工进度,降低施工成本。3)五步单侧壁导坑法中隔壁的最优位置应结合具体工程情况进行单独优化计算,针对本工程而言,其最优位置为45%洞宽。

大断面斋堂隧道爆破近区围岩损伤研究

爆破荷载作用下隧道爆破近区围岩损伤特性研究较少.以斋堂隧道为工程背景,通过现场声波测试和数值模拟的方法,研究了隧道围岩损伤效应及毫秒延期爆破中不同段炮孔对围岩损伤的影响.研究结果表明:隧道围岩损伤范围约为2.4 m,隧道围岩累积损伤由爆炸冲击损伤和爆破振动损伤两部分组成.隧道保留岩体根据损伤分布特征情况可划分为4个不同区域,即严重破坏区、强扰动区、弱扰动区和未扰动区.其中,严重破坏区和强扰动区主要受崩落孔VI和周边孔影响;弱扰动区中的“带状损伤”则是各个段位炮孔综合作用的结果.

厚煤层大断面沿空巷道变形破坏机理及控制技术

针对沿空巷道受多次采动叠加影响极易发生变形失稳破坏的难题,以某矿1505W工作面厚煤层综放开采工作面为研究背景,综合采用理论分析、现场实测、数值模拟等多种研究方法探讨分析了沿空巷道围岩失稳破坏机制,并提出了围岩“浅部、深部、表层”控制方案。现场试验结果表明,提出的控制方案能够使巷道浅、深部围岩形成统一的整体,有效抑制了沿空巷道围岩变形,提高了巷道的稳定性。

高地应力特大断面隧道的适宜施工工法

为探索高地应力特大断面软岩隧道的适宜施工方法,以桐梓隧道为工程背景,通过现场监测和数值模拟,探索不同高地应力下的3种施工工法[三台阶、CD(cross diaphragm)法、双侧壁导坑法]的适宜性,从围岩变形、施工成本以及施工进度等方面评价施工方法的优劣。结果表明:Ⅴ级围岩:当隧道埋深为300、400 m时,适用三台阶法施工;当埋深为500 m时,适用CD法施工;当埋深为600 m时,适用双侧壁导坑法施工。Ⅳ级围岩:当隧道埋深为300~600 m时,都适用三台阶法施工。

大截面变化率对称结构管整体液力成形工艺研究

为解决某汽车排气尾管一体化成形中成形道次多的制造问题,提出了与传统压扁特征处对称结构(A型)设计思路不同的圆截面处对称结构(B型),并采用液力成形工艺对其进行成形,通过对比成形道次和零件质量,分析了两种对称结构工件成形的优缺点。研究发现,由于A型结构工件一道次成形时圆角处会出现裂纹,需采用多工步成形才能实现;而B型结构工件一道次成形效果良好;经多工步成形的A型结构工件和一道次成形的B型结构工件最大壁厚减薄率均小于25%。但是,与A型对称结构工件相比,B型对称结构工件圆角处壁厚减薄率更低,成形效果更好,并且模具数量由3套减少为1套。通过合理的零件结构设计,该结构打破了传统圆形截面端部密封的设计束缚,不仅有效降低了模具成本,还提高了生产效率,大幅提高了零件成形效果。

香炉山隧洞不良地质段“L”型地面超前注浆方案研究

为解决隧道(洞)建设过程中不良地质段突泥涌水和软岩大变形等问题,依托滇中引水工程香炉山隧洞,提出一种采用全孔长度超过500 m的地面“L”型定向钻孔注浆并辅以洞内超前注浆的加固方法,在实际工程中确定这一方法的具体设计方案。首先,通过现场地质调查与分析,揭示不良地质区段香炉山隧洞建设的技术难点;其次,介绍“L”型定向钻孔注浆的施工过程及注浆工艺;然后,设计出一种能够提高地层稳定性的“L”型地面超前注浆方案,并对地层进行加固;最后,采用掌子面揭示、注浆技术以及大地电磁检测等手段证明现场注浆效果。研究结果表明:1)“Z1+Z2+Z4”钻场设计为最优地面超前注浆技术方案;2)“L”型定向钻孔注浆辅以洞内超前注浆技术可满足盲区注浆区域覆盖问题,实现真正意义上的超前治理。

联合深度超参数卷积和交叉关联注意力的大位移光流估计

针对现有深度学习光流估计模型在大位移场景下的准确性和鲁棒性问题,提出了一种联合深度超参数卷积和交叉关联注意力的图像序列光流估计方法.首先,通过联合深层卷积和标准卷积构建深度超参数卷积以替代普通卷积,提取更多特征并加快光流估计网络训练的收敛速度,在不增加网络推理量的前提下提高光流估计的准确性;然后,设计基于交叉关联注意力的特征提取编码网络,通过叠加注意力层数获得更大的感受野,以提取多尺度长距离上下文特征信息,增强大位移场景下光流估计的鲁棒性;最后,采用金字塔残差迭代模型构建联合深度超参数卷积和交叉关联注意力的光流估计网络,提升光流估计的整体性能.分别采用MPI-Sintel和KITTI测试图像集对本文方法和现有代表性光流估计方法进行综合对比分析,实验结果表明本文方法取得了较好的光流估计性能,尤其在大位移场景下具有更好的估计准确性与鲁棒性.

基于围岩应力状态的超大断面隧道深浅埋判定研究

随着目前公路隧道跨度越来越大,而超大跨扁平隧道由于其特殊的形状,使得拱部受力较上圆形隧道更为不利且开挖的影响范围也更大,因此现有深浅埋分界方法的适用性尚需考证。研究采用数值计算与经验公式方法,对比不同跨度、不同围岩级别下超大跨扁平隧道的深浅埋分界,得到适用于此工程的判定方法,同时确定其深浅埋分界范围。研究结果表明:1)主应力旋转轴理论与规范经验法相互补充、相互验证,具有着一定的可操作性,大跨扁平隧道深浅埋分界的判定应结合2种方法综合得到;2)当隧道跨度在19 m左右时,Ⅲ级围岩深浅埋分界值为6 m,Ⅳ级围岩深浅埋分界值为14 m,Ⅴ级围岩深浅埋分界值为34 m。

超大埋深软岩隧道超前中导洞合理断面尺寸及应力峰值转移机制

在超大埋深软岩隧道中,通常地应力较高,且围岩软弱破碎,在施工过程中不可避免地会出现大变形现象,造成支护结构失效破坏。采用超前中导洞应力释放技术提前释放地应力,可以改善支护结构的受力状态,减小隧道变形量,保证支护结构的安全。依托丽香线哈巴雪山大变形隧道,采用文献调研、数值模拟及现场监测等手段对超大埋深软岩隧道超前中导洞合理断面大小进行研究,分析了中导洞不同断面大小工况下应力释放效果,最终确定中导洞合理断面大小。研究结果表明,超前中导洞断面为正洞断面面积的0.6倍时,应力释放效果较为理想,相比直接开挖正洞,采用合理超前中导洞断面时,正洞拱顶沉降及上、下台阶水平收敛值分别减小28.2%、27.64%和26.71%,且围岩中切向应力峰值向围岩深部转移了约4 m,同时,应力峰值数值有所减小,减小约5.04%。研究成果可为类似大变形隧道工程提供参考与借鉴。

松软破碎厚顶煤大跨度切眼变形破坏特征与控制技术

安阳主焦煤矿大断面切眼常采用被动支架沿顶布置,围岩变形量大、易漏冒,工人劳动强度大。针对上述问题,采用数值模拟方法研究了裂隙发育、位移和应力分布与切眼跨度之间的关系,提出了围岩控制策略和支护方案。结果表明,随着切眼跨度的增大,围岩塑性区范围逐渐增加,顶板以剪切滑移或拉剪破坏为主,两帮以泊松效应膨胀拉伸—剪切破坏为主;顶板下沉量、巷帮内挤和底鼓量均逐渐增大;顶煤、直接顶和基本顶部分岩层逐层渐次移动,顶板部分区域出现较大的裂隙,冒落拱以上深部顶板发生整体移动;巷道顶底板中有害拉伸应力区域范围呈现拱形分布,且逐渐增大。根据切眼围岩变形破坏特征,提出了高强度、高刚度、高预紧力的强力支护和被动单体液压支柱补强的主被动联合支护方法。现场工业性试验表明,切眼围岩得到了有效控制,可为类似裂隙发育托顶煤大断面切眼围岩控制提供参考。

深部巷道大断面交叉点联合支护技术研究

针对深部大断面巷道支护易发生失稳的难题,以唐山矿-1100中央轨道山下车场大断面交叉点为工程背景,开展工程地质调查及巷道变形情况分析,提出锚喷+锚注联合支护方案,并运用FLAC3D数值模拟分析支护方案改进前、后巷道变形情况。结果表明,常规锚网喷支护下大断面巷道顶板下沉和帮部位移量较大,巷道不能实现自稳;锚喷+锚注联合支护下巷道变形量大幅降低,巷道基本实现自稳。将该方案应用于工程实践,锚喷+锚注联合支护技术能够有效控制深部大断面巷道变形,顶板下沉量较原支护降低了78.8%,帮部位移量降低了54.8%,为同类工程背景提供可靠的技术参考。