Ground reinforced embankments for rockfall protection: design and evaluation of full scale tests     

D. Peila  C. Oggeri  C. Castiglia 《Landslides》2007,4(3):255-265

Infrastructures such as roads and railways as well as urbanised areas, in mountainside regions, can frequently be endangered by rockfalls and, therefore, need to be protected against the impact of rolling blocks. Among the various protection works that can be used, ground reinforced embankments can be considered a feasible technique. A set of full-scale tests on embankments made of ground reinforced by geogrids are presented and discussed. The experiments were performed in a specifically designed and constructed test facility, where concrete blocks up to 9,000 kg in weight were thrown onto a geogrid reinforced embankment at a speed of about 30 m/s. Several embankments made of different geogrid types, different soils and construction layouts were tested at different impact energy levels, permitting a quantitative assessment of the resistance impact of these structures. The experimental results were compared with those obtained from a dynamic finite element method numerical model, and a good agreement was obtained.  相似文献   

Dynamic capillary effects in heterogeneous porous media   总被引：1，自引：0，他引：1  

Rainer Helmig  Alexander Weiss  Barbara I. Wohlmuth 《Computational Geosciences》2007,11(3):261-274

In standard multi-phase flow models on porous media, a capillary pressure saturation relationship developed under static conditions is assumed. Recent experiments have shown that this static relationship cannot explain dynamic effects as seen for example in outflow experiments. In this paper, we use a static capillary pressure model and a dynamic capillary pressure model based on the concept of Hassanizadeh and Gray and examine the behavior with respect to material interfaces. We introduce a new numerical scheme for the one-dimensional case using a Lagrange multiplier approach and develop a suitable interface condition. The behavior at the interface is discussed and verified by various numerical simulations.  相似文献   

泥石流本构模型及动力学模拟研究现状综述   总被引：9，自引：0，他引：9  

兰恒星  周成虎  王小波 《工程地质学报》2007,15(3):314-321

由于泥石流动力学过程的复杂性,其本构模型及数值模拟研究仍然存在众多的难点问题。本文根据大量的文献资料和实例研究,对目前泥石流本构模型和动力学模拟研究现状和存在的问题进行了综合论述,主要包括:(1)已有泥石流动力学本构模型原理及适用性问题;(2)已有数值模拟方法的实现及选择应用;(3)泥石流动力学复杂环境效应研究,复杂地形和水文环境条件下的泥石流应力分布、动能传递等。最后对泥石流动力学G IS模拟的前景进行了讨论。  相似文献   

井-含水层系统对地下水微动态信息响应能力差异的分析     

张淑亮  程紫燕  唐垒黎 《山西地震》2007,(3):16-20

利用山西地区6口观测井的水位资料,对水震波、前驱波记录次数进行了统计,并对各观测井的潮汐因子、气压效率进行了计算,分析了井-含水层系统对水震波、固体潮、气压、前驱波微动态信息的响应能力,利用井-含水层的特征参数以及含水层的岩性解释了不同观测井对微动态信息响应能力差异的原因。  相似文献   

预应力锚索加固石窟岩体的地震动力响应研究   总被引：2，自引：2，他引：2       下载免费PDF全文

秋仁东  石玉成  徐舜华  胡明清 《地震工程学报》2007,29(1):49-53

根据锚索加固石窟岩体的特点,以甘肃安西榆林石窟的三个典型的工程段为例,通过动力有限元的方法对地震荷载作用下预应力锚索加固石窟岩体的位移场、应力场的模拟计算,得出了其动态响应和变化规律。并通过对地震荷载的频谱特性分析,揭示了地震荷载的特征周期对锚索加固石窟围岩的动力响应结果的影响。  相似文献   

 基于RS与GIS技术的若尔盖地区沼泽动态变化研究   总被引：2，自引：0，他引：2  

王利花  姜琦刚  李远华 《国土资源遥感》2006,17(4):60-62

 采用RS和GIS技术相结合的调查分析方法，引入沼泽动态度等表征参量，探讨了若尔盖地区沼泽的动态变化特征。结果表明： 近30 a来，该区沼泽面积呈现明显的下降趋势，虽然近些年沼泽退化速度有所减缓，但状况仍不容乐观； 沼泽景观破碎化明显，沼泽退化存在着一定的时空变化规律。  相似文献   

宁波地震台水位、地倾斜在印尼8.7、8.5级地震中的同震变化现象     

邱永平 《内陆地震》2006,20(4):336-341

分析了浙江省宁波地震台ZK03井动水位、VS垂直摆倾斜仪资料出现的异常,认为这些异常可能是印尼8.7、8.5级地震的同震变化现象。8.7级地震后,动水位表现为水震波引起的脉冲和阶跃变化并抬高水位。垂直摆倾斜仪资料表现为形变波引起的脉冲和阶跃变化,EW向出现最大幅度约为408.328 2×10-3″的脉冲式向东振荡波,并向西出现阶跃变化;NS向出现最大幅度约为295.191 7×10-3″的脉冲式向北振荡波,并产生向北阶跃变化。8.5级地震后,动水位表现为水震波引起的脉冲。垂直摆倾斜仪资料表现为形变波引起的脉冲和阶跃变化,EW向出现最大幅度约为306.280 9×10-3″的脉冲式向东振荡波,并向西出现阶跃变化;NS向出现最大幅度约为261.565 9×10-3″的脉冲式向北振荡波。  相似文献   

Dynamic melting of the Precambrian mantle: evidence from rare earth elements of the amphibolites from the Nellore–Khammam Schist Belt, South India     

K. Vijaya Kumar  M. Narsimha Reddy  C. Leelanandam 《Contributions to Mineralogy and Petrology》2006,152(2):243-256

The Nellore–Khammam Schist Belt (NKSB) in South India is a Precambrian greenstone belt sited between the Eastern Ghats Mobile Belt (EGMB) to the east and the Cratonic region to the west. The belt contains amphibolites, granite gneisses and metasediments including banded iron formations. Amphibolites occurring as dykes, sills and lenses—in and around an Archaean layered complex—form the focus of the present study. The amphibolites are tholeiitic in composition and are compositionally similar to Fe-rich mafic rocks of greenstone belts elsewhere. The NKSB tholeiites show highly variable incompatible trace element abundances for similar Mg#s, relatively constant compatible element concentrations, and uniform incompatible element ratios. Chondrite-normalized REE patterns of the tholeiites range from strongly LREE depleted ((La/Yb) _N = 0.19) to LREE enriched ((La/Yb) _N = 6.95). Constant (La/Ce) _N ratios but variable (La/Yb) _N values are characteristic geochemical traits of the tholeiites; the latter has resulted in crossing REE patterns especially at the HREE segment. Even for the most LREE depleted samples, the (La/Ce) _N ratios are > 1 and are similar to those of the LREE enriched samples. There is a systematic decrease in FeO^t, K₂O and P₂O₅, as well as Ce and other incompatible elements from the LREE enriched to the depleted samples without any variation in the incompatible element ratios and Mg#s. Neither batch and fractional melting, nor magma chamber processes can account for the non-correlation between the LREE enrichment and HREE concentrations. We suggest that dynamic melting of the upper mantle is responsible for these geochemical peculiarities of the NKSB tholeiites. Polybaric dynamic melting within a single mantle column with variable mineralogy is the likely mechanism for the derivation of NKSB tholeiitic melts. It is possible that the NKSB tholeiites are derived from a source with higher FeO/MgO than that of present day ridge basalts.  相似文献   

Comparison of static-feedforward and dynamic-feedback neural networks for rainfall–runoff modeling     

Yen-Ming Chiang  Li-Chiu Chang  Fi-John Chang   《Journal of Hydrology》2004,290(3-4):297-311

A systematic comparison of two basic types of neural network, static and dynamic, is presented in this study. Two back-propagation (BP) learning optimization algorithms, the standard BP and conjugate gradient (CG) method, are used for the static network, and the real-time recurrent learning (RTRL) algorithm is used for the dynamic-feedback network. Twenty-three storm-events, about 1632 rainfall and runoff data sets, of the Lan-Yang River in Taiwan are used to demonstrate the efficiency and practicability of the neural networks for one hour ahead streamflow forecasting. In a comparison of searching algorithms for a static network, the results show that the CG method is superior to the standard BP method in terms of the efficiency and effectiveness of the constructed network's performance. For a comparison of the static neural network using the CG algorithm with the dynamic neural network using RTRL, the results show that (1) the static-feedforward neural network could produce satisfactory results only when there is a sufficient and adequate training data set, (2) the dynamic neural network generally could produce better and more stable flow forecasting than the static network, and (3) the RTRL algorithm helps to continually update the dynamic network for learning—this feature is especially important for the extraordinary time-varying characteristics of rainfall–runoff processes.  相似文献   

Influence of a cyclic and dynamic loading history on dynamic properties of dry sand, part I: cyclic and dynamic torsional prestraining     

T. Wichtmann  Th. Triantafyllidis 《Soil Dynamics and Earthquake Engineering》2004,24(2):127-147

Initial fabric of a soil induced by its cyclic strain history is an important parameter together with the void ratio, state of stress and amplitude in respect to further accumulation of deformations under drained cyclic loading. It is of importance for the further deformation prediction to determine the initial fabric of the grain skeleton or the cyclic loading history of the soil. An attempt is made within this paper to correlate small strain stiffness of non-cohesive soil with its cyclic loading history. The results of performed cyclic and dynamic torsional tests show that small strain shear modulus is only moderately affected by cyclic prestraining even if high amplitudes are applied. A signature of prestraining history is observed in the tests since the sand memorizes its prestraining amplitude and the number of applied cycles.  相似文献