Impulse control method for hydraulic propulsion system used in 3500 m work-class ROV     

《Applied Ocean Research》2016

In terms of the nonlinear characteristics of hydraulic propulsion system used in 3500 m rated work-class ROV (remotely operated underwater vehicle), the paper improved the responsiveness of the hydraulic propulsion system by adding an impulse signal to the input end of the system. Because the maximum static damping moment provided from water is much larger than the dynamic damping moment, it results in large dead zone of thrust during the startup process of the hydraulic propulsion system. The dead zone of thrust caused by static damping moment can be effectively reduced by adding a specific impulse signal to the input end of the propulsion system. The results of numerical simulations and underwater experiments show that using this method, the nonlinear characteristics of the hydraulic propulsion system have been significantly improved.  相似文献   

Metamorphic P–T profile and P–T path discontinuity across the far‐eastern Nepal Himalaya: investigation of channel flow models     

T. IMAYAMA  T. TAKESHITA  K. ARITA 《Journal of Metamorphic Geology》2010,28(5):527-549

Thermobarometric data and compositional zoning of garnet show the discontinuities of both metamorphic pressure conditions at peak‐T and P–T paths across the Main Central Thrust (MCT), which juxtaposes the high‐grade Higher Himalayan Crystalline Sequences (HHCS) over the low‐grade Lesser Himalaya Sequences (LHS) in far‐eastern Nepal. Maximum recorded pressure conditions occur just above the MCT (～11 kbar), and decrease southward to ～6 kbar in the garnet zone and northward to ～7 kbar in the kyanite ± staurolite zone. The inferred nearly isothermal loading path for the LHS in the staurolite zone may have resulted from the underthrusting of the LHS beneath the HHCS. In contrast, the increasing temperature path during both loading and decompression (i.e. clockwise path) from the lowermost HHCS in the staurolite to kyanite ± staurolite transitional zone indicates that the rocks were fairly rapidly buried and exhumed. Exhumation of the lowermost HHCS from deeper crustal depths than the flanking regions, recording a high field pressure gradient (～1.2–1.6 kbar km^?1) near the MCT, is perhaps caused by ductile extrusion along the MCT, not the emplacement along a single thrust, resulting in the P–T path discontinuities. These observations are consistent with the overall scheme of the model of channel flow, in which the outward flowing ‘HHCS’ and inward flowing ‘LHS’ are juxtaposed against each other and are rapidly extruded together along the ‘MCT’. A rapid exhumation by channel flow in this area is also suggested by a nearly isothermal decompression path inferred from cordierite corona surrounding garnet in gneiss of the upper HHCS. However, peak metamorphic temperatures show a progressive increase of temperature structurally upward (～570–740 °C) near the MCT and roughly isothermal conditions (～710–810 °C) in the upper structural levels of the HHCS. The observed field temperature gradient is much lower than those predicted in channel flow models. However, the discrepancy could be resolved by taking into account heat advection by melt and/or fluid migration, as these can produce low or nearly no field temperature gradient in the exhumed midcrust, as observed in nature.  相似文献   

Haoqin-North Jianshan Thrust Fault and its constraints on the extension of ore-bearing carbonatite in the Bayan Obo areaSCIEI北大核心CSCD     

赵育龙  张继恩  范宏瑞  徐亚  王建  赵永岗  王其伟  谭肖博 《岩石学报》2023,(10):2910-2926

白云鄂博是世界上最大的稀土矿,其资源储量影响着全球稀土资源配置的格局。稀土矿赋存于碳酸岩中,因钻孔深度所限,碳酸岩深部的延伸情况存在争议,是可以延伸较深的岩浆通道,还是根据三维剪切波速度结构研究结果显示的有限深度(约2.5km)。本文在地表展开矿区及周边岩性-构造填图和所卷入岩石的变形特征研究,将剖面上与平面上的构造样式进行对比,将有利于解决上述争议问题。本次研究在好沁、尖山北部、西矿北部一带发现大型逆冲断层,并将其命名为“好沁-尖山北逆冲断层”。该逆冲断层下盘为互层状的(粗)砂岩、灰岩和泥岩,粗砂岩的碎屑磷灰石下交点最年轻群组为1284±104Ma,砂岩的碎屑锆石最年轻组为1179±8Ma,均比白云鄂博碳酸岩的年龄(约1.3Ga)年轻;结合寒武-奥陶纪化石,厘定下盘地层为下古生界。断层上盘为变砾岩、变石英砂岩、板岩和赋矿碳酸岩,变石英砂岩的碎屑锆石存在1.94Ga和2.55Ga的2个峰值,认为其沉积于古元古代。好沁-尖山北逆冲断层将元古代变沉积岩及赋矿碳酸岩推覆于古生代地层之上,断层面上广泛发育断层泥和断层角砾,厚度自20cm至7m不等,沿断层面有含铁质流体灌入而形成赤铁矿,断层面倾角变化大,从水平到直立产状,可能是受后期褶皱影响的结果;结合卷入断层活动的最年轻地质体为二叠纪花岗岩、以及区域内白垩纪不整合沉积在断层及下伏地层之上,限定好沁-尖山北逆冲断层的活动时代发生于二叠纪之后、白垩纪之前。水源头出露有变石英砂岩飞来峰,白云鄂博矿区与南部约30km处发育相似的、4条NE-SW走向的雁列式排列的航磁异常带,它们限定逆冲推覆距离为8~30km。白云鄂博碳酸岩属于推覆体上盘地质体,好沁-尖山北逆冲断层将其与根部错开,白云鄂博地区的碳酸岩未延伸到断层下盘,下盘岩石可能是古生代岩石,因此,矿区深部的剪切波速度突变可能与该断层的发育相关。  相似文献   

雪峰山西侧贵州地区中生代构造特征及其演化   总被引：4，自引：0，他引：4  

刘丽萍  李三忠  戴黎明  王岳军  刘博  金宠  张国伟 《地质科学》2010,45(1)

贵州中生代变形主要发生在燕山期,发育三幕褶皱变形、两幕逆冲和三幕走滑。根据区域对比、卷入褶皱的地层和褶皱间的叠加关系,判断三期褶皱的形成顺序依次为近东西向、北东向和南北向,时限在J_3—K_2之间。逆冲推覆构造主要由向北西或西逆冲的近南北向逆冲断层组成,大体与南北向褶皱同时形成;自雪峰构造带西缘向西,依次划分出根部带、中部带和前锋带。但是,在根部带识别出两幕逆冲推覆,其它两带各识别出一幕。走滑断层也有3个方向:东西向、北东向和近南北向。东西向走滑断层呈现出右行压扭的运动学特征,而大多数北东向走滑断层是左行张扭性质的。依据各个方向断层间的切割和限制关系,推测东西向走滑断层最早形成,其次是南北向逆冲断层,北东向走滑断层最晚活动。这些断裂和褶皱特征,总体表现出贵州多重多种复合联合的构造特征,最后,探讨了本区的构造成因模式。  相似文献   

SHRIMP U–Pb zircon geochronology of the Strzelin gneiss,SW Poland: evidence for a Neoproterozoic thermal event in the Fore-Sudetic Block,Central European Variscides     

T.?Oberc-DziedzicEmail author  K.?Klimas  R.?Kryza  C.?M.?Fanning 《International Journal of Earth Sciences》2003,92(5):701-711

Zircon ages recorded in gneissic rocks have recently been used as criteria to define and correlate various tectonic units and crustal blocks in the central European Variscides. A SHRIMP U–Pb zircon geochronological study of the Strzelin gneiss in the Fore-Sudetic Block (SW Poland) indicates the presence of: (1) inherited zircon cores of Palaeo- to Mesoproterozoic ²⁰⁶Pb-²³⁸U ages (between ca. 2,000 and 1,240 Ma), and (2) zoned rims of Neoproterozoic age with two distinct means of 600±7 and 568±7 Ma. The Proterozoic age range of the cores suggests that different Precambrian crustal elements were the source for the protolith of the gneiss. A likely scenario is the erosion of various Proterozoic granites and gneisses, sedimentation (after 1,240 Ma), and partial resistance of the original components to subsequent metamorphic dissolution and/or anatectic resorption (in Neoproterozoic times). The zoned zircon rims of both of the younger Neoproterozoic ages are indistinguishable in the cathodoluminescence images. The data are interpreted in terms of two different thermal events inducing zoned zircon overgrowth at ca. 600 and 568 Ma. In general, the new results confirm earlier assumptions of the Proterozoic age of the gneiss protoliths, and indicate their similarity to orthogneisses in the East Sudetes tectonic domain (e.g. the Velké Vrbno and Desná gneisses). The Neoproterozoic dates are different from the age of 504±3 reported earlier for the Gocicice gneiss from a neighbouring locality in the Strzelin Massif. The new data strongly indicate a Moravo-Silesian (Bruno-Vistulian) affinity for the Strzelin gneiss and support the hypothesis that the Strzelin Massif lies within the tectonic boundary zone between the West- and East Sudetes domains, which represents the northern continuation of the Moldanubian Thrust.  相似文献   

江西于都-宁都一带印支期构造特征     

朱忠宋鸿林  鲍洪均王知绽 《华东地质学院学报》2004,27(2):153-157

在武夷山中段西侧，即赣南于都—宁都一带，发育北北东向中生代逆冲构造系。该逆冲系由南东往北西逆冲，对其进行构造解析发现，是印支期和燕山期构造的叠加。其中印支期逆冲构造表现有构造窗和飞来峰等，显示缓倾角特征，在空间展布上呈叠瓦状，与晚古生代地层的褶皱相伴生，构成一种褶皱逆冲带型式的构造样式，这期构造被燕山期构造强烈破坏。  相似文献   

The Central Southern Alps (N. Italy) paleoseismic zone: a comparison between field observations and predictions of fault mechanics     

E. Carminati  G.B. Siletto   《Tectonophysics》2005,401(3-4):179-197

The internal sectors of the Orobic Alps (Northern Italy) are characterised by Alpine age regional shortening showing a transition, through time, from plastic to brittle deformation. Thrust faults cut Alpine ductile folds and are marked by cataclasites and, locally, by pseudotachylytes, suggesting that motion was accommodated by seismic frictional slip. In the Eastern Orobic Alps the thrusting initiated at depths deeper than 10 km (the emplacement depth of the Adamello pluton) and possibly continued at shallower depths. This demonstrates that thrust motion occurred between 10 km depth and the brittle-ductile transition, i.e., at mid-crustal depths. The Orobic Alps exhumed paleoseismic zone shows different geometries along strike. In the central sectors of the Orobic Alps, thrust faults, associated with pseudotachylytes, have average dips around 40° and show no pervasive veining. Much steeper thrusts (dips up to about 85°) occur in the eastern Orobic Alps. In this area, faults are not associated with pervasive veining, i.e., fluid circulation was relatively scarce. This suggests that faulting did not occur with supralithostatic fluid pressure conditions. These reverse faults are severely misoriented (far too steep) for fault reactivation in a sublithostatic fluid pressure regime. We suggest that thrust motion likely started when the faults were less steep and that the faults were progressively rotated up to the present day dips. Domino tilting is probably responsible for this subsequent fault steepening, as suggested by a decrease of the steepness of thrust faults from north to south and by systematic rotations of previous structures consistently with tilting of thrust blocks. When the faults became inclined beyond the fault lock-up angle, no further thrusting was accommodated along them. At later stages regional shortening was accommodated by newly formed lower angle shear planes (dipping around 30–40°), consistently with predictions from fault mechanics.  相似文献   

Late Neogene low-angle thrusting on the northwestern margin of the South Carpathians (Poiana Rusca, West Romania)     

Martin S. Oczlon  Dan Onescu 《Tectonophysics》2005,410(1-4):367-377

Mineral exploration drillholes and geoelectric prospecting provide for the first time evidence for thrusting of the South Carpathian Paleozoic basement over northerly adjacent Middle Miocene sediments. Investigations were carried out in two locations, 30 km apart, along the northern margin of the Poiana Rusca Mountains, Romania, southwestern Carpathians. Drill holes in both locations encountered weakly consolidated Middle Miocene clay, sand, and fine gravel below Paleozoic low-grade metamorphic rocks. Intersections from various drill holes demonstrate the presence of low-angle thrusting. Kinematic indicators are so far lacking, but with a thrust direction oriented roughly normal to strike of the Poiana Rusca Mountains, minimum displacement is 1–1.4 km in northwestern or northern direction, respectively. Thrusting occurred most likely during the Late Miocene–Pliocene, whereafter Quaternary regional uplift dissected the thrust plane. In the tectonic framework of Neogene dextral translation of the Tisza–Dacia Block against the southerly adjacent Moesian Platform, transtension appears responsible for Middle Miocene basin formation along the northern margin of the Poiana Rusca region. Proceeding collision of the Tisza–Dacia Block with the East European Craton introduced stronger impingement of the Tisza–Dacia Block against the Moesian Platform, leading to a Late Miocene–Pliocene transpressional regime, in which the northern Poiana Rusca basement was thrust over its adjacent Middle Miocene sediments.  相似文献   

青藏高原典型地区的地貌量化分析——兼对高原“夷平面”的讨论   总被引：18，自引：2，他引：18  

尹安 《地学前缘》2006,13(5):0-0

尽管过去150年以来,人们对于喜马拉雅造山带有很长的一段研究历史,但是对其几何特征、运动方式、动力学演化仍然理解不深。这种情况的出现,主要是因为人们持续关注的是喜马拉雅造山带的二维构造空间特性,并将某些研究程度较高地区的地质关系向外推广到造山带其他地区。就地理、地层及构造划分而言,概念的混淆和误解在有关喜马拉雅的文章中也大量存在。为了阐明这些问题,并为那些有兴趣探究喜马拉雅造山带地质演化过程的人们提供一个新的平台,文中系统地综述了以前的基本观察。我的综述主要是强调沿走向变化的喜马拉雅地质格架在喜马拉雅剥露、变质和前陆沉积方面所起的作用。文章的主要目的是阐明占据造山带核部的大喜马拉雅结晶岩带(GHC)的侵位历史。因为喜马拉雅大部分地区是由主中央冲断层(MCT)和藏南拆离系(STD)之间的GHC所组成,所以在地图和剖面观察上确定这些一级喜马拉雅构造之间的关系是非常关键的。中喜马拉雅出露的平面模式表明,MCT具有断坪-断坡的逆断层的几何特征。南部的逆冲断坪携带了一个GHC的板片(Slab)叠置在小喜马拉雅层序之上(LHS),并形成了一个在MCT逆冲断层带之南延续100km的巨大上盘断弯褶皱。在西喜马拉雅造山带地区,东经约77°处,MCT呈现为横向逆冲断坡(Mandi倾向逆冲断坡)。在其西边,MCT将低级变质的特提斯喜马拉雅层序(THS)叠置到低级变质的小喜马拉雅之上;而在其东边,MCT将高级GHC叠置到低级LHS之上。这种沿走向变化的地层叠置和横穿MCT的变质等级表明,逆冲断层的断距向西减小,可能是由于地壳短缩总量沿着喜马拉雅造山带向西减小所致。在所有出露的地方,STD大致都沿着THS底部的同一地层面,呈现出一个长度>100km的上盘断坪。这种关系说明:STD可能沿着一个先期存在的岩石接触面,或者沿中部地壳近水平的脆性—韧性转换带而发生。虽然喜马拉雅造山带藏南拆离系的上盘都有THS发育,但是至今没有找到THS切断STD下盘的证据。这样使得估算STD的滑动距离非常困难。STD最南端地层或与MCT(即,Zanskar)相交,或者位于MCT前端1～2km的范围内(不丹),这两种可能都暗示MCT与STD在它们向南的上倾(up-dip)方向有可能结合。虽然这种几何特征在现有的模型中几乎被忽略,但对于整个喜马拉雅造山带的变形和剥露历史具有重要的指示作用。  相似文献   

地下采煤的缓倾边坡变形机制     

李俊  刘汉超 《地质灾害与环境保护》1998,9(3):17-24,34

通过某地边坡变形的环境条件和多年监测资料,提出地下采煤的缓倾边坡变形机制,即由地下采煤产生的岩层弯曲下沉侧推效应和央体松动扩容侧推效应,以及地下水作用产生的空隙水压效应导致的边坡变形,并对边坡变形机制进行了验证。  相似文献