黄土丘陵河谷场地地震动特征研究

研究黄土丘陵河谷场地在地震作用下强地面运动特征的变化情况,可以揭示强震对该类场地上震害的触发机理。结合黄土高原的地貌特征,建立具有代表性的动力数值分析模型,通过输入不同幅值、频谱特性和持续时间的地震波,对起伏地形和覆盖黄土层共同影响下的黄土河谷场地进行地震反应分析。结果表明:黄土层和地形耦合作用控制了地表的PGA变化,使其趋于复杂,在同一输入波不同振幅作用下,与基岩河谷各测点相比,黄土覆盖河谷场地的地震动频谱幅值均有所增加,并且频谱主峰均向高频移动。在不同地震波输入下,场地不同部位的固有频率受地形高程和土层影响;而地震动大小和频谱幅值不仅与场地的基本频谱和地形起伏有关,也与输入地震波的频谱成分相关。输入波PGA与地震频谱特征都不变时,同一场地输出的地震频谱形状具有相似的特征,随着地震持时增长,能量向场地基本频率附近集中,从而可能导致场地上相应频率建筑物震动幅值增加,造成累积破坏。     

Bedrock control on the Assu Incised Valley morphology and sedimentation in the Brazilian Equatorial Shelf

The Assu Incised Valley(AIV) is a new example of an incised-valley system located on the Brazilian Equatorial continental shelf.This valley extends over 40 km from the present-day shoreline to the shelf break,in a passive margin setting,on a shallow(~70 m),narrow(43 km) and flat(?1) shelf,with mixed carbonate-siliciclastic sedimentation and a low terrigenous sediment supply.To investigate the morphology of the incised valley and the surrounding shelf area,we analyzed LandSat images and bathymetric,shallow seismic and sedimentological data.The results indicate that the AIV is a coastal-plain incised valley.The incision was mainly forced by the magnitude of the last fall in sea level,which created the specific geometry of valley,atypically widening landward due to lithological and structural control.The AIV is a broad N-S-trending valley with a negative relief of approximately 12 m below the mean shelf topography and low-angle valley walls(~3°),surrounded by a highly planar shelf.The valley is asymmetric in cross-section and subdivided into three segments along the shelf:the landward segment is wide(up to 8 km),shallow( 9 m deep),and 25 km long;the middle segment is narrow(2 km wide),only slightly deeper than the inner segment( 15 m deep) and 10 km long;the outer segment is very narrow( 1 km),has incised relief up to 30 m deep and is 8 km long.The incised valley changes near the shelf break abruptly to a deeper(300 m) and wider submarine canyon(3 km).The three valleysegments are bounded by transfer faults of W-E orientation.In addition,the accommodation-space response to the last deglacial sea-level rise provided a 30 m thick sedimentary fill above a Pleistocene/Holocene regional unconformity and a morphologically controlled stratigraphic organization.The antecedent valley topography controls the sedimentation and hydrodynamics of the modern shelf.Furthermore,the morphology of the AIV is a key example of the control of the bedrock on valley incision and infill response to the last fall and rise in sea level on narrow,shallow and low-gradient shelves.     

LQR control with frequency‐dependent scheduled gain for a semi‐active floor isolation system

Floor isolation is an alternative to base isolation for protecting a specific group of equipment installed on a single floor or room in a fixed‐base structure. The acceleration of the isolated floor should be mitigated to protect the equipment, and the displacement needs to be suppressed, especially under long‐period motions, to save more space for the floor to place equipment. To design floor isolation systems that reduce acceleration and displacement for both short‐period and long‐period motions, semi‐active control with a newly proposed method using the linear quadratic regulator (LQR) control with frequency‐dependent scheduled gain (LQRSG) is adopted. The LQRSG method is developed to account for the frequency characteristics of the input motion. It updates the control gain calculated by the LQR control based on the relationship between the control gain and dominant frequency of the input motion. The dominant frequency is detected in real time using a window method. To verify the effectiveness of the LQRSG method, a series of shake table tests is performed for a semi‐active floor isolation system with rolling pendulum isolators and a magnetic‐rheological damper. The test results show that the LQRSG method is significantly more effective than the LQR control over a range of short‐period and long‐period motions. Copyright © 2013 John Wiley & Sons, Ltd.     

陆地声纳法在探测岩溶区高铁隧道基底隐患中的应用

沪昆高铁的麻拉寨隧道和贵广高铁的高天隧道在联调联试阶段均发生不均匀沉降和底鼓现象,为了摸清隧道基底致灾原因并对注浆质量进行检测研究,采用陆地声纳法在隧道岩溶段进行了检测,在基底下方探测出较多中、小溶洞,多组中、小断层延伸到基底下方使溶洞之间互相连通,由于雨季隧道周边水压力强烈的变化,造成了隧道不均匀沉降与底鼓,根据数据图像的特殊反应确定了破碎区域和浆注入区,依据探测结果确定治理方案并在治理施工中得到验证。      

Evidence of Middle Pleistocene hominin migration in the Qinling Mountains (central China) from the Miaokou Paleolithic site

The Qinling Mountain Range (QMR) spans a large region in China and is an im-portant area of hominin activities.Many Paleolithic sites are found in Bahe,South Luohe,and Hanjiang river valleys in the northern,eastern,and southern part of the range,respectively.The Danjiang River valley acts as a channel connecting these valleys and stretches from the north to the south of the QMR.The previous dating of the Paleolithic sites in the Danjiang valley mainly relied on geomorphologic comparison,stratigraphic correlation,fossil charac-teristics,and Paleolithic artifacts,indicating a lack of absolute data.In this study,we con-ducted a detailed geochronological investigation of the entire valley,and selected an ideal site--the Miaokou profile.Based on the identification of the Ioess-paleosol sequences,opti-cally stimulated luminescence,and magnetostratigraphy,the Paleolithic artifacts of the Mi-aokou site located within the S5 and S6 layers of the profile belong to ～0.6-0.7 Ma.This suggests that the Paleolithic site is an old site in the Danjiang River valley,and this period also witnessed a rapid increase in the number of hominin sites during the Middle Pleistocene.Combining our results with previous reports across the QMR,we propose that the Danjiang River valley might have been a corridor for hominin migration,and is worthy of further inves-tigation.     

Touhuanping Fault, an active wrench fault within fold-and-thrust belt in northwestern Taiwan, documented by spatial analysis of fluvial terraces

This study aims at the recent activity and development of an active wrench fault, the Touhuanping Fault in northwestern Taiwan. Northwestern Taiwan has been proposed in a current situation between the mature to waning collision in terms of tectonic evolution. The main drainage in this area, the Chungkang River, flows close to the trace of the fault mentioned above. We examined various types of deformation of fluvial terraces along the Chungkang River as a key to understanding the nature and rate of the late Quaternary tectonics. The E–W trending Touhuanping Fault has long been mapped as a geological boundary fault, but its recent activity was suspected. Field survey revealed that its late Quaternary activity is recorded in the offset fluvial terraces. Our result shows dextral slip and vertical offset with upthrown side on the south, and activated at least twice since the emergence of terrace 4 (older terrace 3 with OSL date of ca. 80 ka). Total amount of offset recorded in the Touhuanping terrace sequence is 15 m for dextral and 10 m for vertical offset. Estimated recurrence time of earthquake rupture may be a few tens of thousand years. Uplift on the upthrown side of the Touhuanping Fault also resulted in the formation of drowned valleys which were graded to terrace 4. Other deformation features, such as back-tilting, westward warping, and a range-facing straight scarp, were also identified. A second-order anticline roughly parallel to the Touhuanping Fault is suggested to be the origin of the northward tilting on terrace 3; it could have resulted from a flower structure on the Touhuanping Fault at shallow depth. This may demonstrate that the buried segment of the Touhuanping Fault has also been active since 80 ka. In the northern study area, the westward warping at terrace 2 probably represents late Quaternary activity of another NE–SW trending Hsincheng Fault.     

Facies and architecture of a coarse-grained alluvial-dominated incised valley fill: a case study from the Oligocene Gebel Ahmar Formation,Southern Tethyan-shelf (northern Egypt)

Exposures of multistorey, alluvial deposits from the Oligocene Gebel Ahmar Formation in the Cairo-Suez province (north Eastern Desert, Egypt) show the architecture of an up to 35 m thick continuously prograding fluvial/alluvial filling of an incised valley. The Oligocene base level fall resulted in cannibalization of the Eocene bedrock. Subsequent baselevel rise created accommodation space that was filled by deposition of four stacked storeys: lower storeys (1-2) of low sinuosity sandy braid plains and upper storeys (3-4) of gravelly braid plain. These braid plains were sourced from exposed Upper Cretaceous-Eocene and Paleozoic-Lower Cretaceous siliciclastic successions to the south. These successions dominate the Galala-Araba inverted structures. The sandy braid plain channel belts mainly downstream accretion (DA), downstream oblique accretion(DLA), lateral accretion (LA), sandy bedforms (SB), channel (CH), and Hollow (HO) elements, while the gravelly braid plain consists mainly of gravel bars and sheets (GB), gravel-sandstone foresets (GSF), gravel-sand couplets (GSC), and scour pool filling (SPF) architectures. Incised valley incision is potentially linked to a global drop of sea level caused by glaciation, although hinterland tectonism (i.e. Late Cretaceous-Paleogene tectonic inversion and Late Eocene-Oligocene crustal updoming in the source terrains) as well as Late Oligocene-Miocene rifting play a significant role in the subsequent filling. The hinterland tectonism as well as the climate controls the sediment supply. The understanding of the nature of the Oligocene incised valley fill helps in the constrain potential down depositional dip hydrocarbon reservoirs in Nile Delta, East Mediterranean basins, and similar settings in passive continental margins.     

高精度古地貌恢复技术及应用——以辽西凸起南段东营组二段下段为例

辽西凸起南段东营组二段下段发育大型岩性-超覆圈闭,储层发育程度以及分布范围是本区油气富集的主控因素。以油组为单位在低勘探程度区开展高精度古地貌恢复,通过剥蚀量恢复,结合埋深和地震响应特征对原始地层厚度进行了压实恢复,并运用岩性、沉积相以及地震响应特征等对该地区进行古水深校正。通过对研究区沟谷的横截面积及延伸长度定量分析,下切沟谷沿地貌形态和地形坡度由高至低,依次发育V型、U型、W型,其发育横截面积和输砂能力依次降低,且不同时期沟谷形态和发育位置的迁移控制了沉积体系发育特征。精细刻画了不同时期储层分布和沉积体系演化特征。     

利用灰色关联度进行煤层底板突水危险性综合评价的研究与应用

煤层底板水害一直是困扰煤矿安全生产的重要问题之一,选择合理准确的评价方法对煤层底板突水危险性进行评价,对于指导煤矿安全生产有着重要意义。灰色关联度分析法以数据序列为研究对象,现实求各个方案与由最佳指标组成的理想方案的关联系数,再由关联系数得到关联度的方法。将灰色关联度分析法应用到煤层底板突水危险性评价中,建立评价单元与参考序列之间的灰色关联度矩阵,通过引入权重的方式,改进邓氏灰色关联度的计算方法,以保证得到的最终综合评价结果更为准确。     

岷江上游干旱河谷范围的界定及其变化分析

基于1961-2014 年岷江上游及其周边地区20 个气象站点的观测资料,运用Mann-Kendal非参数检验方法分析了研究区近50 a 的气候突变,结合DEM、土壤、水系、土地利用等数据构建了干旱河谷典型特征的诊断指标体系,准确地界定了岷江上游干旱河谷的范围并分析了其气候突变前后的变化。结果表明：（1）研究区气候突变的时间节点为1981 年,当前气候条件（1982-2014 年）下,岷江上游干旱河谷总长度约为151.63 km,面积约705.62 km²（占区域总面积的2.94%）,主要分布于松潘镇江关以下,经茂县凤仪镇至汶川县绵褫间的岷江干流,以及黑水河谷和杂谷脑河谷等岷江支流的两侧。（2）当前气候条件下干旱河谷较气候突变前（1961-1980 年）覆盖河道两岸更宽的范围且向北延伸,长度增加20.87 km,面积增加81.61 km²;（3）气候变暖和土地利用方式的改变是引起岷江上游干旱河谷范围扩大的主要原因。