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941.
942.
Keith M. Clayton 《地球表面变化过程与地形》1997,22(8):721-731
Developments in dating techniques applicable to the late Tertiary and Quaternary are giving us the ability to date past land surfaces. Where reasonable assumptions about the nature of such past surfaces and their partial preservation may be made, they can be reconstructed. This permits the contouring and measurement of the subsequent dissection, allowing not only calculation of the average rate of erosion over the elapsed time, but also information on the pattern of incision. Two examples where this has been attempted are present; both are dissected till surfaces in eastern England, one of Anglian and the other of Devensian age. The approach quantifies the disparity between the incision of valleys and the general denudational lowering of the surface which characterizes many landscapes. The technique is not only of academic interest, but potentially forms a useful line of approach to the assessment of the safety of the burying toxic wastes. © 1997 by John Wiley & Sons, Ltd. 相似文献
943.
944.
由于海水中富集大量可溶性盐类及各种金属离子成分,利用海水配置的海水泥浆具有相对密度大、胶体率低、稳定性差、失水量高等特点,不能满足泥水平衡盾构施工要求。为实现对海水泥浆改性以达到利用海水泥浆维持开挖面稳定,降低穿江越海盾构施工成本,选用CMC(羧甲基纤维素钠)、纤维素PAC(聚阴离子纤维素)、聚丙烯酸铵等8种添加剂进行海水泥浆性质变化试验,优选出对海水泥浆改性明显的添加剂,并分析优选添加剂掺入量和时间对海水泥浆性质的影响规律。同时,基于优选的添加剂CMC,利用泥膜形成试验平台进行改性海水泥浆地层渗透试验。研究表明:不同添加剂对海水泥浆性质变化差异较大,增黏剂PAC、CMC对海水泥浆的改性效果稍好,24 h离析出现浑浊层、混合层、絮凝沉淀层。海水泥浆对地层渗透的滤水量大于改性海水泥浆,泥皮也稍厚,但呈稀疏状态。可以推测,添加剂中和部分海水成分,呈絮凝沉淀,多余添加剂表现出对淡水泥浆的增稠作用。 相似文献
945.
为研究花岗岩残积土的动态冲击性能,开展了高速冲击下的分离式霍普金森压杆(SHPB)试验,与常规应变率下的试验结果比较,分析了高应变率对花岗岩残积土的应力?应变特性和强度的影响。结果表明:低、高应变率下的花岗岩残积土的?-?a(轴向应力?轴向应变)曲线均呈现出软化型。随着应变率 增加,?-?a曲线向?a增大的方向移动,破坏应变?af增加。但高应变率下?af增加的程度更加明显。花岗岩残积土的峰值强度普遍具有应变率依赖性,二者可用直线关系拟合,但低、高应变率下的拟合关系并不一致。提出了率敏性因子m定量评价依赖性强弱。研究发现,随着应变率的提高,强度的应变率依赖性减弱,低应变率下的m为26.694,而高应变率下仅为0.013。相关试验结果指出,高速冲击荷载对土体总体有害。工程中应该采取合理措施控制冲击荷载的危害。该研究有助于深化花岗岩残积土动态冲击性能的理解,为相关工程的施工与设计提供技术参考。 相似文献
946.
947.
948.
Early Identification of the Jiangdingya Landslide of Zhouqu Based on SBAS-InSAR Technology 总被引:1,自引:1,他引:0
SBAS-InSAR technology is characterized by the advantages of reducing the influence of terrain-simulation error, time-space decorrelation, atmospheric error, thereby improving the reliability of surface-deformation monitoring. This paper studies the early landslide identification method based on SBAS-InSAR technology. Selecting the Jiangdingya landslide area in Zhouqu County, Gansu Province as the research area, 84 ascending-orbit Sentinel-1A SAR images from 2015 to 2019 are collected. In addition, using SBAS-InSAR technology, the rate and time-series results of surface deformation of the landslide area in Jiangdingya during this period are extracted, and potential landslides are identified. The results show that the early landslide identification method based on SBAS-InSAR technology is highly feasible and is a better tool for identifying potential landslides in large areas. 相似文献
949.
涉县断裂为太行山隆起区内涉县盆地的控盆构造,走向由NE转为近EW向,倾向NW/N,中部在井店东被EW向断裂错断,是控制涉县盆地的一组断裂。本文采用地质地貌调查、河流阶地分析和地质测年等方法,研究了涉县断裂晚第四纪活动特征。研究发现,涉县断裂带由多组断裂构成,带宽约200m,在清漳河两侧表现为山前的陡崖地貌、基岩破碎变形带,具有正断兼走滑特征,在基岩变形带上部发育走向NNE向和NWW向次级滑动面,次级滑动面错断第四系黄土,最新活动到晚更新世;断裂在盆地区通过,地表形成低缓陡坎,断裂错断Q2-3地层,表现为上陡下缓的正断层。通过对涉县断裂两侧清漳河河流阶地、夷平面和地层年龄综合分析,估算涉县断裂晚更新世以来平均垂直滑动速率为0.06~0.08mm/a,中更新世以来平均垂直滑动速率为0.22~0.34mm/a,垂直差异活动主要发生于中更新世期间。 相似文献
950.
《Limnologica》2020
Competition and predation are the two major biotic interactions in zooplankton community. Various rotifer species exhibit polymorphism in lorica and spine morphology in the presence of predators and competitors, which effectively increases their defence competition capacity. This study compared life-history parameters between long-spined morph (LSM) and short-spined morph (SSM) of Keratella tropica at three temperatures. The results showed that both morphs showed significantly higher intrinsic rate of population increase at 25 °C than those at 20 °C and 30 °C. The intrinsic rate of population increase was significantly lower in LSM than SSM at 25 °C and 30 °C, and the net reproductive rate was significantly lower in LSM than SSM at 30 °C. These results suggested that K. tropica had cost on development of long spines, which, however, was dependent on temperature. Moreover, the competition outcome of LSM and SSM with Moina macrocopa were investigated at three densities of Scenedesmus obliquus (0.5 × 106, 1.0 × 106 and 2.0 × 106 cells/mL) and three initial densities of M. macrocopa (0.1, 0.3 and 0.9 ind./mL), revealing that both LSM and SSM populations decreased significantly at all tested algal densities and Moina levels. LSM showed higher population growth rate than SSM at lower algal density (0.5 × 106 cells/mL) and higher Moina densities (0.3 and 0.9 ind./mL), which suggested that LSM could be more effective to defend M. macrocopa. Three-way analysis of variance showed no significant effects of algal density on population growth rate of K. tropica, but interaction between algal density and M. macrocopa density significantly affected its population growth rate. 相似文献