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11.
The lateral deflection of a cylindrical diaphragm wall and the associated ground movement induced by deep excavation are analyzed by performing site instrumentations and numerical analyses in the coastal area of Korea. Wall lateral deflection, rebar stress, and pore water pressure were measured and analyzed in eight directions. Variations of soil properties with the decrease of confining pressure are compared by performing various in situ tests before ad after excavation. To calculate the wall lateral deflection accurately, the effects of small strain nonlinearity, confining pressure, and the hysteresis loading/unloading loop developed during excavation are considered in the proposed numerical analysis. By comparing numerical results with measured ones, the importances of considering small strain nonlinearity and confining pressure reduction in the nonlinear (FEM) are emphasized. Also, the effects of wall stiffness on the performance of cylindrical diaphragm walls are studied for future similar excavation in the coastal area. 相似文献
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A design procedure is proposed to minimize water infiltration into landfills by optimizing the water diversion length of inclined
covers with capillary barrier effect (CCBE). This design procedure is based on a conceptual, mathematical and numerical approach
and aims at selecting materials and optimizing layer thickness. Selection among candidate materials is made based on their
hydraulic conductivity functions and on a threshold infiltration rate imposed on the designer. The capillary break layer (CBL;
bottom layer) is characterized by a weak capillarity, while the moisture retention layer (MRL; upper layer) is characterized
by a compromise between strong capillarity and high hydraulic conductivity. The thickness of the CBL corresponds to the height
where suction reaches its maximum value for a given infiltration rate. This height can be calculated using the Kisch [Géotechnique 9 (1959)] model. The optimal thickness of the MRL is determined by applying an adaptation of the Ross [Water Resources Research 26 (1990)] model. The results obtained using the proposed design procedure were compared to those obtained from numerical simulations
performed using a finite element unsaturated seepage software. The procedure was applied for two cover systems; one where
deinking by-products (DBP) were used as MRL and sand as CBL and another where sand was used as MRL and gravel as CBL. Using
this procedure, it has been shown that an infiltration control system composed of thin layers of sand over gravel is highly
efficient in terms of diversion length and that its efficiency can be enhanced by placing a hydraulic barrier – such as a
layer of DBP – above the MRL. 相似文献
14.
15.
根据实测河道地形资料,分析了水库下游河床演变中的河岸侵蚀现象,包括不同横向边界约束条件、不同床沙组成和不同河型河段的河岸侵蚀的特征及规律。结果表明:①水库下游均会有河岸侵蚀发生,但初期一般以下切为主,后期以展宽为主。②对于横向边界约束较强的河段,河岸侵蚀相对较弱;相反,则河岸坍塌严重,河岸侵蚀强烈;③对不同的河床组成和边滩组成的河段:河床较粗特别是形成抗冲粗化层,且边滩组成较细的河段,河岸侵蚀现象非常剧烈;河床组成较细的河段,如果边滩抗冲性较强,则河岸侵蚀现象相对较弱,如果滩地组成较细、容易坍塌,河岸侵蚀也会较强;④不同的河型有着不同的河岸侵蚀现象。分汊河段以主汊为主;游荡段的游荡特性在初期受到抑制;弯曲河段的撇弯切滩现象较普遍。 相似文献
16.
David K. Keefer 《Surveys in Geophysics》2002,23(6):473-510
Post-earthquake field investigations of landslide occurrence have provided a basis for understanding, evaluating, and mapping the hazard and risk associated withearthquake-induced landslides. This paper traces thehistorical development of knowledge derived from these investigations. Before 1783, historical accounts of the occurrence of landslides in earthquakes are typically so incomplete and vague that conclusions based on these accounts are of limited usefulness. For example, the number of landslides triggered by a given event is almost always greatly underestimated. The first formal, scientific post-earthquake investigation that included systematic documentation of the landslides was undertaken in the Calabria region of Italy after the 1783 earthquake swarm. From then until the mid-twentieth century, the best information on earthquake-induced landslides came from a succession ofpost-earthquake investigations largely carried out by formal commissions that undertook extensive ground-based field studies. Beginning in the mid-twentieth century, when the use of aerial photography became widespread, comprehensive inventories of landslide occurrence have been made for several earthquakes in the United States, Peru, Guatemala, Italy, El Salvador, Japan, and Taiwan. Techniques have also been developed for performing ``retrospective' analyses years or decades after an earthquake that attempt to reconstruct the distribution of landslides triggered by the event. The additional use of Geographic Information System (GIS) processing and digital mapping since about 1989 has greatly facilitated the level of analysis that can applied to mapped distributions of landslides. Beginning in 1984, syntheses of worldwide and national data on earthquake-induced landslides have defined their general characteristics and relations between their occurrence and various geologic and seismic parameters. However, the number of comprehensive post-earthquake studies of landslides is still relatively small, and one of the most pressing needs in this area of research is for the complete documentation of landslides triggered by many more earthquakes in a wider variety of environments. 相似文献
17.
不同电阻率测深方法对旁侧不均匀体的反映 总被引:2,自引:0,他引:2
利用三维有限元数值模拟,重点研究了旁侧三维不均匀体所产生的视电阻率的影响问题,展示了4种常规电阻率测深法在旁侧不均匀体上的异常分布特点;探讨了测深点正下方目标体异常与旁侧不均匀体异常的区别问题,指出旁侧不均匀体的影响是产生电阻率法假异常的主要原因之一. 相似文献
18.
19.
变参考慢度Born近似傅氏偏移 总被引:1,自引:0,他引:1
针对常规Born近似傅氏偏移方法对于剧烈横向变速介质不能精确成像的状况而提出了变参考慢度Born近似傅氏偏移,理论上解决了任意速度变化地质模型的偏移成像问题。此外,为进一步提高复杂地层的成像精度和波场延拓算子的稳定性,对散射波场的计算公式作了改进。将改进的方法运用于盐丘模型的正演和偏移试验,并与常规Born近似偏移方法相比较,可明显看出变参考慢度Born近似傅氏偏移方法在效果上要优于后者,其处理速度横向变化的能力大大增强。 相似文献
20.
野外调查表明 ,口泉断裂断错了断面附近的 3级地貌面 ,包括大同盆地西侧全新世形成的洪积扇后缘及位于洪积扇冲沟内的Ⅰ ,Ⅱ级阶地。其中冲沟内Ⅱ级阶地为剥蚀阶地 ,Ⅰ级阶地为堆积阶地 ,Ⅰ级阶地面的地层时代距今 2 52ka。在该断裂的悟道及上黄庄 2个地点开挖的大探槽表明 ,在距今 1 2 3万年以来该断裂曾发生 4次古地震事件 ,其中 3次分别发生在接近距今 2 52 ,5 6 8,13 73ka。另一次古地震事件发生在距今 6 76~ 10 82ka。这些数据有可能反映了口泉断裂具备准周期的强震活动。这 4次古地震事件的平均间隔约为 3 74ka ,最新一次古地震与上一次事件的时间间隔约为 3 16ka。 2个大探槽各次事件的平均最小同震垂直位移为 1 8m。这些资料对重新评价口泉断裂未来的地震潜势具有重要意义 相似文献