Current trends of space occupation by encrusting excavating sponges on Colombian coral reefs

Some sponges of the genus Cliona (Porifera, Hadromerida, Clionidae) simultaneously excavate and encrust calcareous substratum, competing aggressively for illuminated space with corals and other organisms. To interpret current trends of reef space occupation, the patterns of distribution and size of three Caribbean species were examined at San Andrés Island and Islas del Rosario in Colombia. While Cliona aprica was ubiquitous, C. caribbaea (= C. langae) preferred deep and protected reef zones, and C. tenuis shallow and wave‐exposed settings. In contrast to the effect on other excavating sponges, chronic exposure to raw sewage did not significantly increase the abundance of the studied sponges. Substratum occupation/availability ratios showed a positive tendency of the sponges toward certain coral skeletons, and a negative or neutral tendency toward calcareous rock, indicating that establishment may be easier on clean, recently dead coral than on older, heavily incrusted substratum. High relief generally limits sponge size to that of the illuminated portions of the substratum. A generally lower proportion of small individuals than of larger ones indicates currently low recruitment rates and low subsequent mortality. Successful events of higher recruitment seem to have occurred for C. tenuis. These are related to the massive acroporid coral die‐off in the early 1980s and to asexual dispersion during storms, resulting in a current 10% substratum cover. Reefs with high coral mortality were and/or are thus more susceptible to colonization and subsequent space occupation by these sponges, although relief may prevent space monopolization.     

桩端土加固处理设计及检测方法的探讨

介绍了人工挖孔桩桩端土承载力不足进行旋喷桩处理的设计过程以及处理后检测过程中遇到的问题。桩端土处理设计可以遵循一般的地基处理设计方法和原则,并针对复合地基承载力检测和桩端土极限端阻力的检测中存在的差异和共同点,提出组合静载荷试验的思路和方法,并在工程中予以实施,并取得了较好的效果。     

港湾广场（一期）深基坑变形监测与分析

深基坑施工变形监测是信息化施工的重要内容,以广州港湾广场(一期)深基坑工程为例,通过对开挖过程中土体水平位移、支护结构侧向位移、支护结构内应力、沉降等监测,结合围护结构的强度检测,采用反演分析对基坑变形进行数值模拟,预测不同开挖深度时基坑的位移变形量,实际监测结果与预测值基本一致,为基坑的设计和施工提供可靠的依据。     

杭州地铁艮山门车站深基坑施工技术研究

针对杭州地铁1号线艮山门车站规模较大且具有下穿道路、防汛河流、盾构始发井、周边高层建筑物和多层建筑物等特点,通过对其深基坑施工技术进行研究,对报警原因进行分析,并采取相应对策,总结出可供杭州市区其他类似的地铁车站施工借鉴和参考的经验。     

膨胀土公路滑坡的形成过程和机理

以国道G316线安康至汉阴段K25膨胀土公路滑坡为例,介绍了滑坡的地质环境条件,阐述了该膨胀土公路滑坡的形态、滑面滑床特征和变形特征以及气象水文、地形地貌和人类工程活动等,内外营力对该滑坡的影响。采用非饱和土强度理论,对滑坡的形成过程和机理进行了详细分析,得出开挖路堑是该滑坡产生的直接原因。其形成过程及机理为:开挖—非饱和滑带土浸水软化,抗剪强度降低或丧失—坡面隆起、坡顶开裂和坡脚剪切破坏—剪切破坏区向上发展与后缘张裂隙贯通—滑面贯通、滑坡产生。     

煤炭绿色开发地质保障体系的构建

掘锚自动化作业是煤矿巷道智能掘进的关键,针对当前掘锚设备交替作业过程中相对位姿测量和碰撞检测难题,提出一种数字孪生驱动的煤矿井下掘锚设备跟踪定位与碰撞检测方法。首先,为克服井下掘进工作面低照度、高粉尘、复杂背景干扰的影响,以多点红外LED标靶作为信息源,通过工业相机采集红外LED特征点图像,利用Hough轮廓检测与质心法提取光斑中心并通过二进制编码识别标靶ID,采用改进稀疏光流算法对光斑进行跟踪,同时建立基于PNP的掘锚设备位姿解算模型,采用对偶四元数获得设备间相对位姿。其次,利用数字孪生技术,基于Unity3D平台建立对应实际尺寸的掘锚设备及工作面数字孪生模型,利用Socket通信方式实现虚拟空间与物理实体之间的实时数据传输与交互,在虚拟空间中实现掘锚设备实时位姿的三维可视化,结合任意多边形OBB(oriented bounding box)碰撞检测算法,实现掘锚设备虚拟碰撞检测。最后,搭建实验平台进行掘锚设备位姿测量试验,同时对虚实运动轨迹和碰撞检测效果进行验证。实验结果表明：掘锚设备跟踪定位实验的位置误差不超过20 mm,角度误差不超过0.30°;虚实位置坐标对比中X轴方向最大误差不超过1.14 mm;Y轴方向最大误差不超过1.10 mm,能够保证系统虚实一致性和同步性,满足掘进工作面作业过程中掘锚设备实时跟踪定位及碰撞检测的要求。

     

Parrotfish mediation in coral mortality and bioerosion by the encrusting,excavating sponge Cliona tenuis

The parrotfish Sparisoma viride often grazes live coral from edges undermined by the Caribbean encrusting and excavating sponge Cliona tenuis. To test whether parrotfish biting action has an effect on the dynamics of the sponge–coral interaction, we manipulated access of parrotfishes to the sponge–coral border in two species of massive corals. When parrotfish had access to the border, C. tenuis advanced significantly more slowly into the coral Siderastrea siderea than into the coral Diploria strigosa. When fish bites were prevented, sponge spread into S. siderea was further slowed down but remained the same for D. strigosa. Additionally, a thinner layer of the outer coral skeleton was removed by bioerosion when fish were excluded, a condition more pronounced in D. strigosa than in S. siderea. Thus, the speed of sponge‐spread and the extent of bioerosion by parrotfish was coral species‐dependent. It is hypothesized that coral skeleton architecture is the main variable associated with such dependency. Cliona tenuis spread is slow when undermining live S. siderea owing to the coral’s compact skeleton. The coral’s smooth and hard surface promotes a wide and shallow parrotfish bite morphology, which allows the sponge to overgrow the denuded area and thus advance slightly faster. On the less compact skeleton of the brain coral, D. strigosa, sponge spread is more rapid. This coral’s rather uneven surface sustains narrower and deeper parrotfish bites which do not facilitate the already fast sponge progress. Parrotfish corallivory thus acts synergistically with C. tenuis to further harm corals whose skeletal architecture slows sponge lateral spread. In addition, C. tenuis also appears to mediate the predator–prey fish–coral interaction by attracting parrotfish biting.     

TPS测设道路填挖边线方法探讨

道路建设中,测设填挖线是经常遇到的问题,就此提出了TPS(全站仪)在任意控制点设站、测定辅助点和填挖点的放样方法。该方法的关键之处是,利用曲线要素推算各放样点的坐标,然后在道路施工现场附近选择一视野开阔的控制点安置TPS,一次性放样出全视野内的辅助点和填挖点,并连接填挖点组成填挖边线。为保证各阶削坡的精度,应注意保护各辅助点的平面位置,正确地削出最上阶平台,以控制以下各阶削坡。而以往的放样方法是抬竿法,需要在逐个横断面多次设站,用定向、量距、抬高的方法放样填挖点。这种方法的缺点是:效率低下,作业难度大,累计误差大。显然,用TPS一次设站,放样若干横断面填挖点的方法,提高了施工效率,降低了作业难度,且提高了放样点的精度。     

关于深基坑水平位移监测方案的探讨

根据深基坑施工的特点,详细介绍了一种监测深基坑水平位移的可行方案。并给出了工程实例。     

天然气管道沟槽石方爆破开挖技术研究

结合西气东输工程聊城至泰安天然气输气管道沟开挖工程的特点,探讨了沟槽石方爆破的设计原则和爆破施工方案。通过选择合适的炮孔布置方式及参数、分段装药结构和起爆顺序,提出了沟槽微差爆破技术以及减小爆破震动和飞石的安全措施,保证了通讯光缆和周围设施的安全,取得了良好的爆破效果,为工程的顺利进行创造了有利条件