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1.
Soil liquefaction and associated ground failures have been a major source of damage during the past earthquakes. The risk of liquefaction and associated ground deformation can be reduced by various ground-improvement methods including the stone column (gravel drain) technique. This paper presents the current state of the stone column technologies as a liquefaction countermeasure. A comprehensive review is provided aiming to: (a) identify key considerations for the general use of stone columns as a liquefaction countermeasure, (b) provide insights for design and construction, (c) compile the latest research developments, and (d) identify sources of useful information. Case histories of field applications and observed field performance are cited to portray different stone column applications and observed effectiveness. The paper identifies areas where more research is needed and includes recommendations for future research and development. 相似文献
2.
Jonathan D. Phillips 《地球表面变化过程与地形》1992,17(7):699-709
Extensive storage of upper-basin Piedmont sediment and apparent low sediment supply to streams in lower-basin Coastal Plain areas generates questions as to the source of alluvium in lower reaches of rivers of the U.S. Atlantic drainage. This was investigated on the Neuse River, North Carolina, using a mineralogical indicator of sediment source areas. The utility of mica flakes for discriminating between Piedmont and non-Piedmont sources of sediment in the lower Coastal Plain reaches of the Neuse was established on the basis of an examination of the U.S. National Soils Database and of 26 soil surveys of the North Carolina Coastal Plain. From the Neuse River estuary to 48 km upstream there are no mica flakes in floodplain soils or in river bank and channel shelf sediments. Mica flakes become more common upstream. This suggests that a very small proportion of the sediment eroded in the Piedmont portion of the watershed is delivered to the river mouth. The small amounts which presumably do reach the lower Coastal Plain are so diluted by Coastal Plain-derived alluvium that no Piedmont origin can be discerned. This demonstrates a dominantly Coastal Plain source and underscores the importance of storage and discontinuous transport in fluvial sediment systems. More importantly, results suggest that upper- and lower-basin sediment dynamics are not only non-linearly related, but may be virtually decoupled. 相似文献
3.
Bedded Permian salt in the Palo Duro Basin of the Texas Panhandle is being considered for isolation of nuclear waste. Studies underway to evaluate the geomorphic processes affecting any waste repository that may be sited in the region include studies of the geomorphic events associated with individual storms. On 26 May, 1978, thunderstorms occurred near Canyon, Texas, which received 130mm of rain, and on a small instrumented watershed at Buffalo Lake, 16 km to the southwest, which received 71 mm of rain. Rainfall at Buffalo Lake was concentrated in a period of 3 hours, representing a return period of approximately 10 years and a maximum 30-minute intensity of 64 mm/hour. Erosion-pin fields, topographic surveys, and stakes for headcut monitoring had been established 2 to 3 months before the storm in a 640-m long tributary canyon to Tierra Blanca Creek downstream of Buffalo Lake. Canyon slopes of moderately to slightly calichified sands and gravels of the Ogallala Formation are capped by well-indurated caliche on the canyon rim. Erosion-pin fields showed average net erosion of 2·4 cm (0° to 9° slope) to 2·7 cm (10° to 19° slope) and a single-pin maximum value of 6·2 cm in the 20° to 29° slope class. Headcuts 1 to 2 m deep in alluvial-colluvial material on the floor of the canyon migrated as much as 12 m upstream. Canyon floor deposition occurred as a series of elongate bars, 16m long and longer, located at the mouth of tributary gullies, downstream from scours, and at slope breaks. Grain sizes ranged from boulders up to 70cm in intermediate axis deposited in the upper canyon to fine to very fine sand deposited as a sheet up to 25cm thick beyond the mouth of the canyon at Tierra Blanca Creek. In an adjacent canyon a sequence of irregular beds of caliche gravel, mixed sand and gravel, and fine sand up to 3 m thick is exposed. Comparison of this sequence with deposits resulting from the 26 May, 1978, storm suggests that the coarse fraction of the alluvial sequence is deposited by repetitive major storm events. Cobble and boulder units 30 to 70cm thick can evidently be deposited in a few hours. Under the continental climate of the Texas Panhandle, erosion, deposition, and stream incision are taking place primarily in discrete steps related to episodes of intense rainfall. 相似文献
4.
在郯庐断裂带的安丘—夏庄箕状盆地的古近纪朱壁店组厚层冲积层中,发育许多震积岩层。它们是由地震液化、地震裂隙充填、振动塌落、地震断裂和地震沉陷作用而形成的震积岩组合。通过野外观测、室内鉴定和比较地震地质学研究,鉴别出了液化砂岩脉、液化砂岩墙、液化砂岩团块、裂隙充填砂砾岩墙、震塌岩、地震成因层内断裂及地震沉陷构造等震积岩构造。根据震积岩构造的特征和有关的研究成果,本文建立了由A、B和C3个震积岩单元组成的震积岩序列。水饱和砂受强烈振动液化作用形成A单元;随后,由砂砾层或砂层的地震裂隙充填和震动塌落而形成B单元;最后,由层内断裂作用及地面沉陷作用生成C单元;该序列的3个单元反映了厚层冲积物的地震作用全过程。 相似文献
5.
Local geology or local site effect is a crucial component while conducting seismic risk assessment studies. Investigations made by utilization of ambient noise are an effective tool for local site estimation. The present study is conducted to perform site response analysis at 13 different sites within urban settlements of Fateh jang area(Pakistan). The aim of this study was achieved by utilizing Nakamura method or H/V spectral ratio method. Some important local site parameters, e.g., the fundamental frequencies f0 of soft sediments, amplitudes A0 of corresponding H/V spectral ratios, and alluvium thicknesses over 13 sites within the study area, were measured and analyzed. The results show that the study area reflects low fundamental frequency f0. The fundamental frequencies of the sediments are highly variable and lie in a range of 0.6–13.0 Hz. Similarly, amplification factors at these sites are in the range of 2.0–4.0. 相似文献
6.
Catastrophic flood effects in alpine/foothill fluvial system (a case study from the Sudetes Mts, SW Poland) 总被引：1，自引：0，他引：1
Tomasz Zielinski 《Geomorphology》2003,54(3-4):293-306
Depositional effects of two great floods in the Nysa drainage basin have been studied: the alluvial forms and deposits of channels and floodplains. Three types of bars and one overbank form were found in the mountain streams, and four types of bars and three types of overbank forms have been distinguished in main rivers. A specific spatial succession of depositional forms was recognized along the mountain streams, however, no analogous phenomena were noted within the main river valleys. Several types of bars and alluvial lithofacies have been regarded as characteristic effects of the catastrophic flood. The study indicates that the Nysa river is close to the threshold of metamorphosis to a typical braided fluvial system. 相似文献
7.
John Pitts 《地球表面变化过程与地形》1986,11(1):107-110
An approximate method is described for determining the maximum consolidating pressure in a hard, heavily overconsolidated fissured clay. From this, the overburden thickness producing the observed degree of consolidation has been calculated. The normal method of calculating preconsolidation pressure using an oedometer was not possible. The ratio c/p' is used in conjunction with the undrained shear strength. Values of c/p' are determined using empirical relationships with Atterberg Limit values. The results allow an overburden thickness to be calculated by assuming a value for unit weight. 相似文献
8.
Transport of suspended solids from a karstic to an alluvial aquifer: the role of the karst/alluvium interface 总被引：1，自引：0，他引：1
N. Massei M. Lacroix H. Q. Wang B. J. Mahler J. P. Dupont 《Journal of Hydrology》2002,260(1-4):88-101
This study focuses on the coupled transport of dissolved constituents and particulates, from their infiltration on a karst plateau to their discharge from a karst spring and their arrival at a well in an alluvial plain. Particulate markers were identified and the transport of solids was characterised in situ in porous and karstic media, based on particle size analyses, SEM, and traces. Transport from the sinkhole to the spring appeared to be dominated by flow through karst: particulate transport was apparently conservative between the two sites, and there was little difference in the overall character of the particle size distribution of the particulates infiltrating the sinkhole and of those discharging from the spring. Qualitatively, the mineralogy of the infiltrating and discharging material was similar, although at the spring an autochthonous contribution from the aquifer was noted (chalk particles eroded from the parent rock by weathering). In contrast, transport between the spring and the well appears to be affected by the overlying alluvium: particles in the water from the well, showed evidence of considerable size-sorting. Additionally, SEM images of the well samples showed the presence of particles originating from the overlying alluvial system; these particles were not found in samples from the sinkhole or the spring. The differences between the particulates discharging from the spring and the well indicate that the water pumped from the alluvial plain is coming from the karst aquifer via the very transmissive, complex geologic interface between the underlying chalk formation and the gravel at the base of the overlying alluvial system. 相似文献
9.
The Bhuj, India, earthquake of 26 January 2001, Ms 7.9, caused dams built on alluvium to sustain damage ranging from cosmetic to severe. Major damage was caused almost entirely by soil liquefaction in the alluvium. The critical factor was the level of earthquake ground motion.
The Bhuj earthquake showed that peak horizontal accelerations (PHAs)≤0.2 g were generally safe. PHAs>0.2 g were hazardous, when unconsolidated granular foundation soils were water saturated. N values of <20 are indicative of susceptibility to soil liquefaction. The Bhuj experience showed that alluvial foundation soils, subject to a PHA>0.2 g, must be evaluated over the full area beneath a new dam and all soils deemed susceptible to liquefaction must be either removed or treated. For remediating an old dam, reliable options are removal and replacement of liquefiable alluvium beneath upstream and downstream portions of the dam, combined with building berms designed to provide stability for the dam should there be a strength loss in soils beneath the dam. 相似文献
10.
河谷深厚覆盖层工程地质特性及其评价方法 总被引：2，自引：1，他引：2
河谷深厚覆盖层广泛分布于我国大江大河中，其研究对加我国水利水电工程建设具有重大。意义。文中以川西河流为例，论述河谷深厚覆盖层的基本特征及工程地质特性，并重点论述河谷深厚覆盖层的承载力、变形 、强度参数及渗透特性的评价方法。 相似文献