自动剪断线在线状要素合并中的应用

本文在详细分析线要素的拓扑关系和弧段拓扑建立中的自动剪断线方法的基础上,引入扫视求交法,重点探讨了自动剪断线算法在线状要素合并中的应用。通过合并自相交与线状要素之间相交两步过程,引入求交前的预处理,提高了自动剪断线的效率。最后对本方法进行了简单的试验分析。     

安溪黄厝坪铁矿区复杂地层钻孔护壁堵漏实践

福建省安溪县黄厝坪铁矿区地层复杂,设计钻孔2个。01孔钻探中遇多孔段漏失,反复采用多种堵漏方法顺利终孔,但严重影响了钻探效率。经过总结经验和教训,在02孔施工中,对护壁堵漏措施进行了完善,较好地解决了钻进漏失问题,取得了良好的效果。介绍了2个钻孔的护壁堵漏过程,总结了在破碎漏失严重地层的堵漏对策以及堵漏方法的选择经验。     

河南西峡含化石碎屑龟山组层位层序及时代探讨

信阳群龟山组横贯北秦岭南缘及桐柏山—大别山，西延入陕西，为地质结构上的关键层位，部分地段为重要赋矿层位，因其为一套罕见化石的碎屑岩，故对其地质时代看法颇异。近年我队在西峡八庙矿区工作时，在岩石薄片中见有多门类化石碎屑，并作了报道。作者在报道的基础上，吸收前人和近年某些有关信阳群和刘岭组（群）的工作成果，就龟山组的层位、层序及时代进行探讨，并与邻区、邻省的相关层位进行对比：认为含动物化石碎屑的龟山组（周进沟组）与陕西省的牛耳川组及桐柏山—大别山北坡的大部分龟山组及二郎坪群和部分苏家河群的时代大体相当，其时代归属暂置早奥陶世—早泥盆世     

The Role of India-Asia Collision in the Amalgamation of the Gondwana-Derived Blocks and Deep-Seated Magmatism During the Paleogene at the Himalayan Foreland Basin and Around the Gongha Syntaxis in the South China Block

Southeast Asia comprises collage of continental blocks that were rifted out in phases from the northern parts of the Gondwanic Indo-Australian continent during the Paleozoic-Mesozoic time and were accreted through continental collision process following closure of the Paleo- and Neo-Tethys. The South China and Indo-China blocks were possibly rifted during early Palaeozoic, whereas, the Tibetan and SIBUMASU blocks were rifted during Permo-Carboniferous when the said margin was under glacial and/or cool climatic condition. The Indo-Burma-Andaman (IBA), Sikule, Lolotoi blocks were also rifted from the same Indo-Australian margin but during late Jurassic. This was followed by break-up of the Indian and the Australian continents during early Cretaceous. The opening of the Indian Ocean during the Tertiary was synchronous with closing of the Tethys.India-Asia collision during early-middle Eocene was a mega tectonic event. Apart from initiating the Himalayan orogeny and the eastward strike-slip extrusion of the Indochina block from the Southeast Asian continental collage along the Ailao Shan — Red River shear zone, it also caused early-mid Eocene continental-flood-basalt activity in the Himalayan foreland basin. Indian continent's post-collisional indentation-induced syntaxial buckling of Asian continental collage at its eastern end possibly caused late Paleogene highly potassic magmatism around the Gongha syntaxial area that was located close to the sutured margin of South China continent with Indochina block at the outer fringe of Namche Barwa syntaxis. These magmatic bodies are soon after left-laterally displaced by the Ailao Shan — Red River shear zone. The nature and chemistry of magma at these two settings indicate that both groups result from similar petrogenetic and tectonic processes representing deep-seated melts due to mantle decompression. Some deep faults produced at the edge of flexed Indian continental lithosphere and responsible for the development of the foreland basin may have produced continental-flood-basalt and related magma by decompressional melting of enriched sub-continental mantle. The site-specific location and time sequence of magmatism from the marginal parts of South China continent and located at the outer fringe of Namche Barwa syntaxis are strongly significant. It suggests that these magmatic bodies may also be genetically related to the India-Asia collision process and indentation-induced syntaxial buckling of upper mantle beneath the marginal parts of the South China rigid continent.     

Zero graffiti for a beautiful city: the cultural politics of urban space in San Francisco

San Francisco, like many cities in the United States and across the world, has an official zero-tolerance policy on graffiti. In this article, we examine the academic literature concerned with graffiti and then present a case study of zero-tolerance abatement policies in San Francisco. Our analysis yields three main findings. First, zero-tolerance policy stimulates an anti-graffiti industry with vested interest in perpetuating an endless war for control of public space. Second, zero tolerance may generate an unintended result—the proliferation of tags and other forms of graffiti that people tend to dislike the most. Third, we find little evidence that the general public shares the same desire for zero tolerance as the San Francisco Government. Ultimately, we believe that more nuanced readings of graffiti allow greater numbers of people to make sensible, local, place-specific policies regarding graffiti.     

煤矿深部巷道破裂围岩非线性大变形及支护对策研究

针对淮南矿区顾北煤矿-648 m水平南翼回风大巷围岩处于破裂状态,且表现出强烈非线性力学现象的特点,采用离散元计算软件UDEC,分析其变形破坏过程及非线性大变形机制,并在此基础上提出应用分步联合支护的技术方案进行支护,进而通过数值模拟与现场监控量测相结合的方法进行分析验证。结果表明,破裂围岩开挖后的变形破坏过程是一个渐近发展的过程,局部关键块体的垮落或滑移是导致其他部位失稳和巷道产生非线性大变形的主要原因;分步联合支护技术能实现巷道的长期稳定性,是一种有效控制深部巷道破裂围岩非线性大变形的支护型式。     

尾矿坝垮塌机制与溃决模式试验研究

基于云南拉拉铜矿小打鹅尾矿库工程设计资料,采用现场排放尾矿砂为试验材料,进行了尾矿堆积坝在洪水情况下发生垮塌破坏的模型试验。通过水流控制系统模拟尾矿坝遭遇洪水情况,采用侧面示踪点、水位测压管、应力传感器以及数码摄像机等设备获得了尾矿坝溃决过程中坝坡的位移矢量演化、浸润线与应力的变化特性以及坝体破坏发展过程,揭示了洪水作用下尾矿坝的垮塌机制和溃决模式。试验结果发现：尾矿堆积坝的浸润线变化存在滞后性;在洪水入库致库区最高设计洪水水位过程中,靠近坝坡中部处水平方向的总应力增量较垂向总应力增量大,增大的水平应力是坝体产生破坏的重要因素之一;洪水导致坝坡尾矿砂所受的渗透力、上浮力、重力以及孔隙水压力增大,削弱了坝体材料的黏聚力,并加大了自身荷载,降低了坝体的稳定性;尾矿坝溃决模式一般为逆流渐进型,破坏先是从坡脚处发生,继而向上游发展,呈现牵引式发展,破坏的滑动面由多个弧形滑移面构成。研究成果加深了对尾矿堆积坝垮塌机制和溃决模式的认识,并在洪水灾害的预防和控制方面作了一些新的探索     

大松动圈围岩锚网索联合支护参数确定方法探讨

对大松动圈围岩巷道,单一锚杆支护难以实现对整个破裂区围岩的锚固控制,采用锚网索联合支护时,应考虑锚杆支护对联合支护设计的作用。通过分析大松动圈围岩锚杆锚固支护机制,提出量化锚杆支护作用的锚固承载系数,形成锚网索联合支护参数量化计算方法。研究结果表明：锚杆锚固支护后将大松动圈围岩分为浅层锚固区和深层破裂区,浅层锚固区具有一定承载能力,可视作锚索的等效托盘;在锚网索联合支护中,浅层锚固区承载结构稳定的条件是锚固结构承载力大于环向轴力且能够有效控制破裂区围岩;锚固承载系数大小主要取决于浅层锚固区与破裂区和锚杆预紧力与设计锚固力的关系,对于大松动圈围岩其取值范围为0.45～0.75。经现场试验可知,巷道顶底板移近量为273 mm,两帮移近量为393 mm,表面位移曲线趋于平稳,采用该方法得到的锚网索支护参数有效保证了巷道的正常使用。     

加载历程对配径碎煤渗透特性影响的试验研究

为了证实加载历程对破碎煤样渗透特性的影响,利用一套由齿轮泵、换向阀、溢流阀和渗透仪等组成的渗透回路,在CMT5305型电子万能试验机试验系统上测试了配径碎煤在两种不同试验方案下的渗透特性,得到了两种方案配径碎煤的渗流速度、渗透率、非Darcy流? 因子与孔隙度的关系。研究表明：①第1种试验方案的渗流速度和渗透率与孔隙度的关系用幂函数拟合,第2种试验方案的渗流速度和渗透率与孔隙度的关系可用指数函数拟合。②孔隙度较大时,渗透率和非Darcy流? 因子与加载历程有关;孔隙度较小时,渗透率和非Darcy流? 因子趋于稳定,与加载历程无关。③随着孔隙度的减小,方案1非Darcy流? 因子由负变正,配径碎煤的渗透性加强;方案2非Darcy流? 因子始终为负值,配径碎煤的渗透性减弱。④两种方案的非Darcy流? 因子与孔隙度均可采用三次多项式拟合,多项式的系数与加载历程有关。     

基于锚杆抗拔试验的动态折线模型分析

根据抗拔锚杆试验数据,建立了锚固体荷载传递特性随锚固深度变化的动态折线数值计算模型。首先,对锚杆抗拔试验进行了简单介绍,给出了试验的主要参数及数据;在此基础上,对试验中抗拔锚杆不同深度处锚固体荷载传递曲线进行了对比分析和讨论,提出了用以拟合计算的动态折线模型;然后结合锚杆轴力及位移计算能量法计算式对试验数据进行了拟合计算,计算结果与试验数据吻合,显示在拟合计算中动态折线模型使用合理;最后通过讨论明确了动态折线模型的适用条件,说明了其在试验分析及工程设计中的辅助作用。动态折线模型反映了不同深度地层中地应力变化对锚侧阻力的影响,虽然在计算中没有直接引入地应力,但其以试验为基础的参数设置和相对简单的迭代计算,为更精细的计算锚杆承载力提供了参考。