A fossil record of shell boring: Possible evidence for sea level changes in the Red Sea     

Ehud Spanier   《Estuarine, Coastal and Shelf Science》1987,24(6)

An aggregation of fossil shells of the Indo-Pacific muricid snails Chicoreus ramosus was found in the northern part of the island of Tiran, Red Sea. The site was 7 m above the present mean sea level. Radiocarbon dating of these shells indicated an age of 1570±80 years BP. Some of these shells bore-drilled holes, most of them uncompleted. Biological study revealed that such holes were probably drilled by conspecifics in the absence of alternative food after they had been disconnected from the sea. Since there is no evidence of human activity in this part of Tiran, I suggest that such conditions could be caused only by a physical process that changed the relative water level. In accordance with the character of the drilled holes and the short period which muricids maintain reproductive aggregates, I also postulate that such a physical process must have been a relatively rapid one.  相似文献   

武汉地区岩溶地层钻孔灌注桩成孔技术研究与实践          下载免费PDF全文

訾兵 《探矿工程》2009,36(11):36-38

随着城市基础设施建设及城市化进程的加快,有更多的钻孔灌注桩设计在岩溶地层。在岩溶地层进行钻孔施工容易发生孔内事故,且出现频率较高,处理难度很大,经济损失较大。通过对溶洞裂隙发育的石灰岩地层进行注浆加固,然后进行钻孔桩成孔工艺的试验研究。结果表明,该方法在比较好的解决了石灰岩地层成孔效率低、孔内事故多及泥浆混凝土漏失的技术问题。对岩溶地层进行钻孔桩施工具有重要的参考意义。  相似文献   

刘塘坊铁矿1号副井井筒冻结钻孔施工实践          下载免费PDF全文

王兵  汪志祥  董梅  李宏伟 《探矿工程》2011,38(4):53-57

介绍了冻结法施工的原理和特点;简述了刘塘坊铁矿1号副井井筒冻结钻孔的基本情况,分析了本工程施工的难点和采取的技术措施,介绍了施工中需要注意的事项和环节,对本工程进行了施工总结。  相似文献   

A numerical model of beach morphological evolution due to waves and currents in the vicinity of coastal structures   总被引：2，自引：0，他引：2  

Pham Thanh Nam  Magnus Larson  Hans Hanson  Le Xuan Hoan 《Coastal Engineering》2011

A numerical model was developed of beach morphological evolution in the vicinity of coastal structures. The model includes five sub-models for random wave transformation, surface roller development, nearshore wave-induced currents, sediment transport, and morphological evolution. The model was validated using high-quality data sets obtained during experiments with a T-head groin and a detached breakwater in the basin of the Large-scale Sediment Transport Facility at the Coastal and Hydraulics Laboratory in Vicksburg, Miss, USA. The simulations showed that the model reproduced well the wave conditions, wave-induced currents, and beach morphological evolution in the vicinity of coastal structures. Both salient and tombolo formation behind a T-head groin and a detached breakwater were simulated with good agreement compared to the measurements.  相似文献   

A model of tunnel boring machine performance   总被引：2，自引：0，他引：2  

G. Wijk 《Geotechnical and Geological Engineering》1992,10(1):19-40

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以钻代坑坑钻组合勘探在水口山矿的应用     

周运秋  雷治坤 《湖南地质》1992,11(4):331-333,348

水口山矿在几十年的勘采过程中,摸索出一套以钻代坑、坑钻结合行之有效的探矿工艺途径,在提高矿山近期开采储量级别;对矿体探边扫盲、延长服务年限;代替坑道探矿、查明老窿及含水构造,保证井下安全作业等方面都取得了很好的成绩,地质经济效益显著。  相似文献   

Settlement and colonization of epi‐endobenthic communities on calcareous substrata in an underwater archaeological site          下载免费PDF全文

Edoardo Casoli  Sandra Ricci  Andrea Belluscio  Maria Flavia Gravina  Giandomenico Ardizzone 《Marine Ecology》2015,36(4):1060-1074

Underwater archaeological sites represent assets of great value that are subjected to physical and biological stresses. The study of biological settlement on calcareous substrata is the first step to understanding the biodeterioration processes that take place on man‐made structures (marble, statues, columns and other architectonic elements) in marine environments. To accomplish this objective, calcareous panels (30 × 30 × 2 cm) were immersed for 3, 6, 9 and 12 months along a north?south transect in marine protected areas of Baia (Naples). Both epilithic and endolithic assemblages were analysed: the latter was observed by scanning electron microscope after the cast‐embedding technique had been used. After 1 year the epilithic community was still changing, with algae and pioneer species overgrown by encrusting organisms, and the endolithic assemblage dominated by cyanobacteria/chlorophyte traces. Changes of epilithics lead changes on endolithics. The initial phototrophic borers were replaced by more sciophilous and competitive species; moreover, the first macroboring organisms arrived after the settlement of grazers. After 12 months of immersion, the rate of bioerosion was high, the material was deeply bored and all of the limestone surface was heavily covered.  相似文献   

Columnar microbialites of the upper Miocene of Mallorca (Spain): A new morphogenetic model based on concurrent accretion and bioturbation – uncommon or overlooked?     

Pablo Suarez-Gonzalez  M. Isabel Benito  Concha Arenas  Luis Pomar 《Sedimentology》2022,69(1):88-120

Bioturbation has long been considered an antagonist of microbialite development and preservation, because metazoan grazing and burrowing destroy benthic microbial communities. However, metazoan bioturbation, in conjunction with microbial accretion, may have had a significant role in the morphogenesis of some columnar microbialites, as suggested by the case study presented and by some Phanerozoic and Upper Proterozoic analogues discussed here. Late Miocene in age, the studied microbial biostrome developed in a western Mediterranean restricted shallow-water platform dominated by grainy sediments and with a notable influence of bioturbation. This study is focused on the complex accretionary history of the columnar microbialite biostrome and on its striking dark grey colour, which is attributed to Mn-oxyhydroxides precipitated during meteoric diagenesis linked to subaerial exposure. The characteristic columnar structure of the microbialite biostrome has features consistent with an accretionary origin of the columns, but also has features suggesting metazoan disruption. Therefore, a new morphogenetic model for columnar microbialites is presented, highlighting the concomitant roles of microbial accretion, bioturbation and grainy sediment infill of the intercolumn space. Whether this model is an exception or a rule, should be tested on other examples of Phanerozoic and Upper Proterozoic columnar microbialites. Nevertheless, this model is a step forward in understanding the complex microbe–metazoan interactions as constructive coexistence rather than just as destructive competition.  相似文献   

碾压混凝土结构的接缝灌浆技术     

张发明  陈俊 《地球科学与环境学报》1999,21(2):2

在碾压混凝土结构中进行接缝灌浆,是目前坝工研究的重要技术问题。以某工程为例,详细分析了影响接缝灌浆质量的因素,提出了特殊条件下接缝灌浆的技术方法  相似文献   

深部复合地层TBM开挖扰动模型试验研究     

史林肯  周辉  宋明  卢景景  张传庆  路新景 《岩土力学》2020,41(6):1933-1943

针对全断面隧道掘进机（TBM）开挖过程掌子面岩体软硬交替变化的特点,以兰州水源地建设工程为背景,采用模型试验与数值模拟方法研究了复合地层TBM开挖过程隧洞围岩的动态响应规律。通过开展相似配比试验配制了不同围岩强度比的复合地层岩体相似材料,运用光纤光栅技术全程捕捉了隧洞开挖过程复合地层应变演化规律,并分析了隧洞围岩的宏观破裂形态。模型试验结果表明：TBM推进过程中复合地层应变变化规律体现了掌子面推进的空间效应,软岩部分应变要大于硬岩部分应变,且随着开挖步数的增加两种岩层应变差值越大;隧洞内岩体完全挖除后,围岩宏观破裂形态表明因复合地层岩体物理力学性质的差异,上覆软岩变形破坏较为严重,破裂和变形较为显著,在软、硬岩层交界面出现“变形不协调”现象。选取工程沿线某洞段的地质力学参数,基于破坏接近度（FAI）指标评价了隧洞开挖过程中复合地层围岩的稳定性,数值结果表明：开挖过程软岩中FAI变化较为明显,塑性区和破坏区分布范围更广,而下部硬岩受开挖扰动影响较小,只有拱底小范围岩体进入破坏状态。模型试验和数值结果均说明交替变化的掌子面岩体在开挖过程中其围岩在变形破坏等规律方面存在明显差异,因此,TBM在复合地层施工可采取重点部位监测预警、提前采取相应措施等手段,减少或避免卡机事故的发生。该研究成果对于指导复合地层TBM施工具有一定的借鉴和指导意义。  相似文献