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海床在波浪作用下是否稳定对海底工程的安全至关重要,海床的稳定性与土体中的孔压响应密切相关。水槽模拟试验表明:在波浪的作用下,黄河三角洲粉土海床中将产生振荡孔隙水压力和累积孔隙水压力。振荡孔隙水压力大小与土层深度、波高和粘粒含量有关,其振幅(能量)在土层中随深度的增加呈指数衰减,且粘粒含量越高衰减越快;加载波高越大,能量衰减越快。而累积孔压响应模式表现为在波浪作用最初的一段时间内,孔隙水压力快速上升,然后逐渐减小而趋于稳定,其大小和速率也与波高、粘粒含量、土层埋深有关,粘粒含量越高,孔压累积速度越低。 相似文献
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黏粒含量对粉质土液化发生的作用机制 总被引：4，自引：0，他引：4
近年来,海岸沉积的粉质土在波浪作用下发生液化的问题开始被关注和研究。由于粉质土中含有黏粒成分,其液化机制可能与砂性土不同。通过对不同黏粒含量的粉质土进行循环荷载三轴试验,获得孔压、应变的变化曲线。以应变5%为土体破坏标准,结合土体的微结构特征,分析认为粉质土由于黏粒含量不同,存在液化破坏和触变破坏两种导致液化发生的机制。 相似文献
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动荷载作用下海底粉土的孔压响应及其动强度 总被引：5，自引：0，他引：5
本文选用近海分布较广的粉土为研究对象 ,利用室内动三轴试验结果 ,找出动荷载作用下粉土的动应力应变关系 ,分析模拟波浪荷载作用下粉土中的孔压响应、临界循环次数 ,确定波浪作用下粉土的应力状态、破坏临界循环次数 ,判断不同深度处的粉土发生液化的可能性及发生液化所需要的时间 ;研究粉土在动荷载作用下的强度降低 ,为海上工程设计和施工提供科学依据。 相似文献
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《海洋地质与第四纪地质》2017,(1)
粉质土底床在波浪作用下发生液化,发现有液化发展和液化沉积两个过程。以粉质土铺设底床开展波浪水槽试验,通过测试贯入阻力、含水量、密度、中值粒径和黏粒含量在液化过程中随时间的变化,给出粉质土在液化过程中物理力学性质的变化规律。试验给出:总体上,粉质土底床液化层在液化发展过程中强度急剧降低,含水量增加,密度减小,中值粒径增大,黏粒含量减少;在液化沉积(固结)阶段强度增大,含水量减小,密度增大,中值粒径增大,黏粒含量减少。 相似文献
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波浪加载下海底土质特性变化的研究 总被引：3，自引：0，他引：3
通过不同的制样方法 ,在水槽中模拟了多种海底在波浪作用下的变化行为。试验发现 ,加压排水固结的砂质粉土海底在波浪作用下较稳定 ;加压不产生排水而固结的砂质粉土海底易受波浪的冲刷 ;自然条件和轻微振动的砂质粉土海底最易受到波浪的扰动破坏 ,形成塌陷凹坑。粘粒含量较高的粉质粘土对波浪的反映不敏感 ;下卧软土层土体在上覆压力下的变形量与含水量关系密切 ,含水量越高 ,变形越大。试验结果证明 ,波浪会引起沉积物性质发生改变 ,也是引起海底形态变化的主要原因。 相似文献
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为研究深海能源土在负压开采过程中含气储层的力学特性,基于含气土赋存理论,提出一种能够控制含气量及气泡大小的制样方法,通过GDS标准应力路径三轴试验系统,开展深海能源土含气储层的固结排水试验研究,分析深海能源土在不同黏土含量及不同含气量下的力学响应规律。研究结果表明：围压变化对深海能源土含气储层的抗剪强度峰值大小影响显著,围压越大抗剪强度峰值越高;黏土含量是决定应力应变曲线变化趋势的关键影响因素,黏土含量越高试样抗剪强度越低,试样抵抗应变软化效应的能力越强;含气土比饱和土体承载能力更低,且承载能力随含气量的增大呈衰减趋势;黏土含量和含气量是深海能源土含气储层抗剪强度指标的重要影响因素,黏土含量、含气量越高,土体自身的总抗剪强度值越低。 相似文献
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Using data from laboratory, field, and numerical experiments, we investigated regularities in changes in the relative limit height of breaking waves (the breaking index) from peculiarities of nonlinear wave transformations and type of wave breaking. It is shown that the value of the breaking index depends on the relative part of the wave energy in the frequency range of the second nonlinear harmonic. If this part is more than 35%, then the breaking index can be taken as a constant equal to 0.6. These waves are spilling breaking waves, asymmetric on the horizontal axis, and are almost symmetric on the vertical axis. If this part of the energy is less than 35%, then the breaking index increases with increasing energy in the frequency range of the second harmonic. These waves are plunging breaking waves, asymmetric on the vertical axis, and are almost symmetric on the horizontal axis. It is revealed that the breaking index depends on the asymmetry of waves on the vertical axis, determined by the phase shift between the first and second nonlinear harmonic (biphase). It is shown that the relation between the amplitudes of the second and first nonlinear harmonics for an Ursell number less than 1 corresponds to Stokes’ second-order wave theory. The empirical dependences of the breaking index on the parameters of nonlinear transformation of waves are proposed. 相似文献
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风浪破碎对平衡域内谱形的影响 总被引：1，自引：0，他引：1
孙士才 《中国海洋大学学报(自然科学版)》2000,30(1):29-35
在实验室测得的大量风浪资料的基础上,经过谱分析和破波概率的计算,发现风浪破碎概率P 相似文献
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The characteristics of dynamic stress in the seabed under wave loading are constant principal stress and continuous rotation of the principal stress direction.Cyclic triaxial-torsional coupling shear tests were performed on saturated silt by the hollow cylinder apparatus under different relative densities,deviator stress ratios and vibration frequencies to study the development of pore water pressure of the saturated silt under wave loading.It was found that the development of pore water pressure follows the trend of "fast～steady～drastic".The turning point from fast to steady stage is not affected by relative density and deviator stress ratio.However,the turning point from steady to drastic stage relies on relative density and deviator stress ratio.The vibration cycle for the liquefaction of saturated silt decreases with increasing deviator stress ratio and increases with relative density.The vibration cycle for the liquefaction of the saturated silt increases with vibration frequency and reaches a peak value,after which it decreases with increasing vibration frequency for the relative density of 70%.But the vibration cycle for the liquefaction of saturated silt increases with vibration frequency for the relative density of 30%.The development of pore water pressure of the saturated silt is influenced by relative density and vibration frequency. 相似文献
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深水风浪破碎发生率与风速和风区的关系 总被引：1，自引：0，他引：1
徐德伦 《中国海洋大学学报(自然科学版)》1994,(1)
根据于渤海中部采油平台测得的数据，结合实验室的测量，提出一种深水风浪破碎发生率与风速和风区关系的经验公式，与现已发表的少量海上测量结果相比较，此式符合良好。利用此式较好地解释了风浪破碎起始风速问题。 相似文献
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Although a number of programmes for the visual estimation of breaking wave height have been, or are being, operated in different parts of the world (USA-LEO, Australia-COPE), there has been little investigation of the reliability of such data to make precise evaluations of breaking wave height. Using a combination of field data for simultaneous visual estimations and measurements of breaking wave height, it can be shown that experienced observers are able to estimate mean height with only a 20% error. Also the moments of the breaking wave spectrum may be calculated, allowing quick and cheap measurements of extreme waves.LEO records from Florida and California indicate that almost 50% of the data are redundant as frequency of observation could be halved without loss. However, records appear to be filtered, inasmuch as extreme waves are underestimated. 相似文献
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总结破碎波近年来的研究状况，从理论上对计算破碎波发生率进行分析。并利用先进的实验设备和良好的现场条件，从实验研究出发，在研究波浪破碎过程及其与环境参量的关系中，对破碎波发生率进行实际测量。利用不同的破碎波判据对破碎波发生率进行了计算、比较和分析，结果指出；利用不同的破碎波判据计算的破碎波发生率相差很大，甚至相差３～４倍。 相似文献
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In an attempt to elucidate the mechanics of deep-water wave breaking, a variety of breaking waves, including spilling and plunging waves, of different length scales and geometries was studied. The waves were generated through wave-wave interactions using wave packets with constant-steepness components, constant-amplitude components, and also components following the Pierson-Moskowitz distribution. Wave steepening prior to breaking were found to cause an increase in the high frequency spectral slope of the wave spectrum. The slopes were correlated to the type of breaking and the intensity of the breaking. The energy loss through breaking varied with the spectral characteristics of the wave packet. On the other hand, it was also noted that, irrespective of the wave packet, the losses were from the higher frequency end of the first harmonics. 相似文献
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Electrode polarization is a major problem in the determination of dielectric properties of samples, particularly at low frequencies.
Understanding of these interfacial phenomena is essential in order to measure correctly the electrical properties of a sample
of interest. This paper presents a comparative study of the effect of electrode contact impedance on A.C. electrical properties
of a partially and fully saturated hematitic sandstone sample. The electrical properties of the sample were first measured
using stainless steel electrodes with high contact impedance, and measured again with a four terminal Cu–CuSO4 electrode of low contact impedance. Complex impedance measurements at room temperature (~16°C) were performed in the frequency
range from 1 Hz to 100 kHz. Measured electrical spectra vary strongly with the electrode type. The difference in the electrical
properties between the two electrode types (stainless steel and Cu–CuSO4) may be attributed to the surface contact impedance between the sample and the electrode. Experimental data indicate that
the electrical properties vary strongly with water saturation. The dielectric constant decreases with frequency and increases
with saturation up to a certain saturation limit then decreases. Charge transport can occur either through the bulk of the
solid matrix (hematite or sand) or along the grain boundaries of aggregates (water). When soil minerals are exposed to water,
exchangeable ions go into solution. Most of the ionic or covalent bonded rock forming minerals such as quartz, mica, and feldspars
are nonconductors. When the surfaces of these minerals come into contact with liquid water, electrolytes are formed and ionic
drift associated with the electrical field causes electrical conduction. The anomalous dielectric properties of partially
saturated rocks can be interpreted using percolation theory. This theory predicts that when the conductive fraction (water)
increases, clustering of conductive inclusions develops, and the thickness of insulating gaps between conductive clusters
decreases, causing a large increment in the capacitance of the sample. Further increases in the conductive component causes
the shunting of insulating capacitive gaps. 相似文献
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Ambient noise in the surf zone, in the frequency range 120 Hz to 5 kHz, was recorded using a broad-band hydrophone, located approximately 1 m above bottom and 1-2 m below the mean sea surface. The predominant source of this noise is breaking waves. Analysis of simultaneous land-based video observations of the sea surface in the region of the hydrophone, along with wave height data, reveals quantitative correlation between wave-breaking events and the hydrophone signal. In energetic surf, locally breaking waves appear as discrete events in the ambient noise spectra. Distant breaking events do not appear to be detected, as distinct events above the ambient background noise, by the hydrophone. The noise events associated with local breakers are characterized by an asymmetry in the time envelope: low frequencies (less than 500 Hz) are observed leading the breaking crest, followed by a broader range of frequencies peaking in intensity with the passage of the wave crest above the hydrophone, and then decreasing abruptly at all frequencies. Low frequencies are generally not observed trailing the breaking wave. The detection by the hydrophone of breaking waves in the immediate vicinity implies that ambient noise in heavy surf provides a means of studying breaking-wave statistics in the surf zone in situ: in particular, the frequency of occurrence of local breaking 相似文献
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我国东海陆架地区新生代地层的热导率 总被引：10，自引：0，他引：10
对东海陆架区的浅表层柱状岩芯样品和多口钻井岩心样品的热导率数据按岩性、深度、年龄和孔隙度进行了统计分析。发现泥岩、粉砂岩和砂岩的热导率有所不同。在3000m以上，泥岩的热导率大于砂岩的热导率；而在3000m以下砂岩的热导率则大于泥岩的热导率。粉砂岩的热导率基本介于泥岩和砂岩之间。岩石的热导率和岩石样品所处的深度密切相关，随着深度的增大热导率数值增大。岩石的年龄影响岩石的热导率。在同等深度的情况下，年龄越老，热导率数值越高，但埋深浅的老地层热导率会小于埋深大的新地层的热导率。孔隙度和含水对岩石样品的热导率有很大的影响，岩石会因孔隙中含水而使热导率有非常大的变化。本文给出了饱和水热导率和干样热导率之差和孔隙度的回归方程。 相似文献