Sponges boring into precious corals: an overview with description of a new species of Alectona (Demospongiae, Alectonidae) and a worldwide identification key for the genus     

Barbara Calcinai  Carlo Cerrano  Nozomu Iwasaki  & Giorgio Bavestrello 《Marine Ecology》2008,29(2):273-279

Precious corals represent peculiar substrata for several species of boring sponges that exploit their carbonatic scleraxis, strongly decreasing their commercial value. Here we describe a new species of the genus Alectona from Japan recorded in a colony of Paracorallium japonicum (Kishinouye, 1903). The spicular complement of the new species consists of diactinal spicules covered by mushroom-like tubercles, often modified into styloid forms, and fusiform amphiasters with two or sometimes four verticils, each generally made up of six short tubercled rays. A complete survey of the literature on boring sponges recorded in precious corals in the Mediterranean Sea and Pacific Ocean indicates that the species of the family Alectonidae are the most strictly associated to this kind of substratum. Their world distribution, in fact, partially or totally overlap that of their coral hosts.  相似文献   

非开挖铺管导向钻进中的事故处理   总被引：2，自引：0，他引：2  

史晓亮  李粮纲 《地质与勘探》2000,36(2):60-62

根据导向钻进法在实际管线铺设施工中遇到的孔内事故 ,阐述了处理常见孔内事故的措施 ,并提出了避免事故发生的建议。  相似文献   

Environmental factors shaping boring sponge assemblages at Mexican Pacific coral reefs     

Héctor Nava  José Luis Carballo 《Marine Ecology》2013,34(3):269-279

Recent studies suggest a future increase in sponge bioerosion as an outcome of coral reef decline around the world. However, the factors that shape boring sponge assemblages in coral reefs are not currently well understood. This work presents the results of a 17‐month assessment of the presence and species richness of boring sponges in fragments collected from living corals, dead coral reef matrix and coral rubble from Punta de Mita and Isabel Island, two coral reefs from the central coast of the Mexican Pacific Ocean. Both localities have a high cover of dead corals generated by past El Niño Southern Oscillation events, but Punta de Mita was also highly exposed to anthropogenic impacts. Additionally, environmental factors (water transparency, water movement, temperature, sediment deposition, SST, and chlorophyll concentration) were assessed to test the hypothesis that environmental conditions which are potentially harmful for corals can enhance sponge bioerosion. Isabel Island and Punta de Mita showed a similar species richness (13 and 11 species, respectively) but boring sponge presence in both live and dead corals was higher at Isabel Island (57.6%) than at Punta de Mita (35.7%). The same result was obtained when each type of substrate was analysed separately: dead coral reef matrix (81.3% versus 55.5%), coral rubble (47.7% versus 20.0%) and living corals (43.7% versus 31.7%). A principal components analysis showed a higher environmental heterogeneity at Punta de Mita, as well as important environmental differences between Punta de Mita and Isabel Island, due to sediment deposition (2.0 versus 0.2 kg·m^?2·d^?1) and water movement (24.5% versus 20.5% plaster dissolution day^?1), that were also negatively correlated with boring sponge presence (r = ?0.7). By analysing the boring sponge assemblage, we found that environmental settings, together with habitat availability (i.e., dead coral substrate) differentiated assemblage structure at both localities. Major structural differences were largely due to species such as Cliona vermifera, Cliona tropicalis and Aka cryptica. In conclusion, factors such as habitat availability favored the presence of boring sponges but some environmental factors such as abrasion resulting from moving sediment acted restrictively, and exerted a major role in structuring boring sponge assemblages in the Mexican Pacific.  相似文献   

Prediction model of tunnel boring machine performance by ensemble neural networks     

《Geomechanics and Geoengineering》2013,8(2):123-128

The penetration rate of a tunnel boring machine (TBM) depends on many factors ranging from the machine design to the geological properties. Therefore it may not be possible to capture this complex relationship in an explicit mathematical expression. In this paper, we propose an ensemble neural network (ENN) to predict TBM performance. Based on site data, a four-parameter ENN model for the prediction of the specific rock mass boreability index is constructed. Such a neural-network-based model has the advantages of taking into account the uncertainties embedded in the site data and making appropriate inferences using very limited data via the re-sampling technique. The ENN-based prediction model is compared with a non-linear regression model derived from the same four parameters. The ENN model outperforms the non-linear regression model.  相似文献   

长螺旋CFG桩处理软地基的研究与应用     

杨礼锋  张建平 《中国煤炭地质》2012,(2):50-52

长螺旋钻机成孔CFG桩施T是近年来新兴的一项基础工程施工技术,在工程建设领域有着广泛的应用,尤其适用于对软土地基的处理。该技术施工噪声低,成桩速度快,效果好,得到了广大施工技术人员的青睐。CFG桩复合地基可以大大提高地基承载力,减小地基的沉降,进而满足设计要求。本文介绍了长螺旋钻机成孔CFG桩的成桩工艺流程、理论设计、质量控制措施,并以工程实例进行佐证,以期该施工技术得到更加广泛应用和发展。  相似文献   

非开挖导向钻进轨迹的三维模拟与调控设计   总被引：1，自引：1，他引：0       下载免费PDF全文

乌效鸣  高辉杜峰 《探矿工程》2001,(5):45-46,49

应用空间解析方法和计算机三维图形技术,科学地模拟非开挖导向钻井时钻头在地下的立体坐标位置、倾角、面向角和运行路线,准确、快捷地调控非开挖导向钻井的钻孔设计轨迹。  相似文献   

潜孔锤旋挖钻机组合在基岩桩施工中的应用          下载免费PDF全文

谭现锋  朱学顺  胡克祯  孟焕梅 《探矿工程》2006,33(7):22-23,26

空气潜孔锤钻进工艺和旋挖钻机钻进工艺相结合，充分发挥了潜孔锤对硬、脆、碎基岩地层施工小口径速度快的优越性，也发挥了旋挖钻机施工大口径速度快的优越性，同时也拓宽了旋挖钻机对中～硬基岩施工的领域，提高了旋挖钻机施工中～硬基岩桩基的效率，为旋挖钻机施工类似中～硬基岩提供了技术参考和经验借鉴。  相似文献   

螺旋扩底注浆成桩技术的应用     

于长龙 《中国煤田地质》2002,14(3):55-56,59

通过对螺旋扩底注浆村技术在沈阳城区的应用介绍，说明了该技术的应用优点及应用范围；论述了该技术单桩承载力设计参数的确定；分析该技术在应用过程中影响单桩承载力的几个因素，并对施工中遇到不良地质的情况下提出处理意见，再通过工程实例论证该技术在沈阳城区的应用情况，以其得到广泛的使用。  相似文献   

多功能液压桩孔钻机          下载免费PDF全文

黄振德  王伟平 《探矿工程》2001,(5):19-21

多功能液压桩孔钻机是一种高效率、多用途的灌注桩成孔设备，它能够快速地改变机器形态，配备长螺旋钻、短螺旋钻、筒形钻、岩石钻等钻具进行旋挖成孔，配备摆管器等钻具进行全套管护壁成孔，或者配备各种抓斗实施地下连续墙作业。介绍了多功能液压桩孔钻机的结构及特点。  相似文献   

坑内单管水力反循环取心钻探技术研究     

陈礼干 《矿产与地质》2001,15(4):284-289

阐明了坑内水力反循环连续取心钻进的原理以及该工艺所具有优点、缺陷及相应的工艺措施。提出了该工艺规程参数的计算原理及计算方法。  相似文献