Phytoplankton,especially diatoms,in the gut contents and feces of two plantivorous cyprinids—Silver carp and bighead carp     

Xie Ping  Liu Jiankang 《中国海洋湖沼学报》1994,12(4):308-315

In order to clarify whether the planktivorous silver carp and bighead carp can collect phytoplankton as small asCyclotella(<20 μm) in Donghu Lake, studies on phytoplankton in their gut contents and feces were made in 1990. The fish were cultured in both net cage in Donghu Lake and aquaria with the lake water. Past the intestine, the average valve diameter ofCyclotella changed little. The average ratio of empty frustule ofCyclotella to totalCyclotella in the foregut contents of the fishes were 1.8–1.9 times higher than that in the lake water, but changed little from foregut to feces. The aquarium experiment showed that both carps could collect particles as small as 8–10 μm, which was obviously narrower than the distance between their gill rakers. Probably, secretion of mucus plays an important role in collecting such small particles.  相似文献   

液化地层震动沉管桩施工对策     

赵以龙 《中国煤田地质》2007,19(A01):67-67,77

南京某综合办公楼桩基工程采用震动沉管桩，由于该区地层的粉砂层存在不同端阻力分界面，因上层长时间的震动，下层粉砂层发生液化，导致桩尖与沉管脱离，桩管内出现水泥浆：为此在施工中采用活瓣桩尖，并用0．5m^3的砼封底，有效地解决了桩管冒浆问题。  相似文献   

油压冲击器的工作原理及仿真电算研究     

陈宝义  王清岩  赵向东 《吉林地质》2004,23(2):72-75

在阐述油压冲击器特点的基础上，进行了较深入的内部工作理论研究，建立了冲击器的数学模型并进行了仿真电算研究，为油压冲击器的研制打下了基础。  相似文献   

Development of fluid conduits in the auriferous shear zones of the Hutti Gold Mine, India: evidence for spatially and temporally heterogeneous fluid flow   总被引：1，自引：0，他引：1  

Jochen Kolb  Amanda Rogers  F. Michael Meyer  Torsten W. Vennemann 《Tectonophysics》2004,378(1-2):65-84

The gold mineralization of the Hutti Mine is hosted by nine parallel, N–S trending, steeply dipping, 2–10 m wide shear zones, that transect Archaean amphibolites. The shear zones were formed after peak metamorphism during retrograde ductile D₂ shearing in the lower amphibolite facies. They were reactivated in the lower to mid greenschist facies by brittle–ductile D₃ shearing and intense quartz veining. The development of a S₂–S₃ crenulation cleavage facilitates the discrimination between the two deformation events and contemporaneous alteration and gold mineralization. Ductile D₂ shearing is associated with a pervasively developed distal chlorite–sericite alteration assemblage in the outer parts of the shear zones and the proximal biotite–plagioclase alteration in the center of the shear zones. D₃ is characterized by development of the inner chlorite-K-feldspar alteration, which forms a centimeter-scale alteration halo surrounding the laminated quartz veins and replaces earlier biotite along S₃. The average size of the laminated vein systems is 30–50 m along strike as well as down-dip and 2–6 m in width.Mass balance calculations suggest strong metasomatic changes for the proximal biotite–plagioclase alteration yielding mass and volume increase of ca. 16% and 12%, respectively. The calculated mass and volume changes of the distal chlorite–sericite alteration (ca. 11%, ca. 8%) are lower. The decrease in δ¹⁸O values of the whole rock from around 7.5‰ for the host rocks to 6–7‰ for the distal chlorite–sericite and the proximal biotite–plagioclase alteration and around 5‰ for the inner chlorite-K-feldspar alteration suggests hydrothermal alteration during two-stage deformation and fluid flow.The ductile D₂ deformation in the lower amphibolite facies has provided grain scale porosities by microfracturing. The pervasive, steady-state fluid flow resulted in a disseminated style of gold–sulfide mineralization and a penetrative alteration of the host rocks. Alternating ductile and brittle D₃ deformation during lower to mid greenschist facies conditions followed the fault-valve process. Ductile creep in the shear zones resulted in a low permeability environment leading to fluid pressure build-up. Strongly episodic fluid advection and mass transfer was controlled by repeated seismic fracturing during the formation of laminated quartz(-gold) veins. The limitation of quartz veins to the extent of earlier shear zones indicate the importance of pre-existing anisotropies for fault-valve action and economic gold mineralization.  相似文献   

三维快速拉格朗日法在安全顶板厚度研究中的应用   总被引：11，自引：2，他引：11  

李廷春  李术才  邱祥波  陈卫忠 《岩土力学》2004,25(6):935-939

为了合理选择厦门海底隧道的最小顶板厚度。在厦门海底隧道轴线的地质部面图上，选取了6个典型剖面，在不同的剖面及同一剖面的隧道的不同深度，应用三维快速拉格朗日法，分两个步骤：第1步，在较大的深度范围内初选隧道的顶板厚度：第2步，在第1步初选结果的基础上，在较小的深度范围内，进一步选择。通过对开挖后的应力分布、洞周位移、塑性区等的分析，最后得出厦门隧道的最小顶板厚度。同时，得到一些对后续施工和其他工程有一定指导意义的有益结论。  相似文献   

大型换流站阀厅结构地震响应弹塑性分析   总被引：1，自引：0，他引：1  

韦文兵  吴轶  蔡健  杨春  唐冬  陈寅 《地震工程与工程振动》2011,31(5):113-120

利用有限元方法对带悬挂阀的阀厅结构进行地震响应弹塑性分析,研究不同场地土条件、不同地震动作用对阀厅结构以及悬吊设备地震响应的影响.研究结果表明:阀厅结构在纵向和三向地震作用下存在较明显的扭转效应;三向地震输入时,吊杆产生的拉力约为单向输入的2倍;悬吊设备竖向地震响应大于水平地震响应,大震下悬吊设备竖向加速度约为水平向的...  相似文献   

淮北煤矿大口径排水孔施工技术          下载免费PDF全文

耿洪州  叶礼明 《探矿工程》1994,(4):30-32

着重论述了淮北煤矿大口径排水钻孔的施工方法及成井工艺。采用满眼钻具防斜，确定上、中、下扶正器安装的最佳位置，利用喷射钻进提高钻进效率，利用管底逆止阀浮力塞解决下管及注浆的难题。  相似文献   

混凝土联锁排应用于海底管线冲刷防护试验研究     

张宗峰  丁红岩  刘锦昆 《海洋工程》2015,33(2):77-83

海底管道冲刷防护是海管研究的热点之一,混凝土联锁排具有整体性好、易于机械化施工等优点在保滩护底工程中得到广泛应用。在易受意外荷载作用的近海冲刷区域,将"混凝土联锁排+土工布"防护型式引入海底管道冲刷防护中,针对裸露或悬空海底管线,探讨混凝土联锁块的防护机理,开展室内水槽试验,选取不同水深工况对比冲刷防护效果并验证了土工布的反滤防护作用,经过分析对比表明"混凝土连锁排+土工布"防护型式适用于海底管线的防护。  相似文献   

高渗压小水力梯度岩石渗透性测试   总被引：1，自引：0，他引：1  

徐德敏  黄润秋  虞修竟 《岩土力学》2010,31(4):1103-1107

对低渗透岩石的渗透性测试一般采用瞬时压力脉冲法,但该方法不能真实模拟野外高孔隙水压力、小水力梯度的现场实际条件,而且试验存在较大误差。为此开发研制了一套新型高压渗透仪,在渗透出水端安装了管路过滤器、调速阀两种器械元件,可手动任意调控流量大小,而流量大小采用精确测量渗出水体积变化量表示。试验只要保证进水端水压不变,当调控的水流量与试样的渗流量达到平衡时,则会在出水端形成一个稳定的水压值。该套试验设备不但可对圆柱体试样进行渗透性、力学特性测试,而且还可以对方柱体试样进行渗透性测试,实现了对岩石实际所处应力、高孔隙水压力环境的真实模拟。实测检验理论技术可行,达到了满意的试验效果。  相似文献   

舟山灌门水道海底隧道钻爆法施工稳定性分析   总被引：1，自引：0，他引：1  

蔚立元  李术才  徐帮树 《岩土力学》2009,30(11):3453-3459

以舟山灌门水道海底隧道为背景,依据地质资料,选取隧道典型横断面来研究钻爆法施工时围岩的稳定性。由典型横断面的几何参数和地质资料构建数值计算模型,采用国际上常用的计算模式模拟爆破荷载,根据FLAC3D动态计算的特点,将爆破荷载以等效应力的方式加载于模拟炮孔之上。数值计算结果表明,各关键点的位移、振动速度、加速度-时程曲线均满足隧道爆破变形规律,且振动速度峰值均小于规范要求临界值,爆破作用影响范围小于岩石覆盖层建议厚度,验证了岩层覆盖厚度建议值和爆破方案的合理性。最后,为了弄清岩石覆盖厚度和炸药量对围岩稳定性的影响,给出了不同岩石覆盖厚度和炸药量情况下的计算结果。所得结论对后续施工和类似工程具有一定的指导意义。  相似文献