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将砂与黏土按不同比例干重量均匀混合制成砂-黏混合土,进行不排水三轴剪切试验,研究了含砂量和试验围压对混合土初始切线模量和应力-应变关系的影响,并对其作用机理进行了分析。研究结果表明:含砂量小于50%时,可以认为混合土初始切线模量与含砂量无关。含砂量大于50%小于80%时,初始切线模量随含砂量增加呈线性趋势增长。通过把含砂量参数引入到初始切线模量中对Duncan-Chang模型进行修正,使修正后的模型能够描述含砂量小于80%时混合土的应力-应变关系。当含砂量超过80%,混合土呈应变软化型,随含砂量的增加,初始切线模量逐渐保持稳定,应力-应变曲线峰值应变左移,可应用软化模型对其应力-应变关系进行描述。围压对混合土应力-应变关系有很大影响,在双对数坐标中,随试验围压的增大,初始切线模量呈线性趋势增长。 相似文献
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本文利用非线性理论分析了震前形变能随时间的演化关系，导出了应力与应变的本构关系为非线性时的突变演化模型。最后利用青海门源６．４级地震前后的跨断层形变资料，计算了非线性形变的演化过程。取得如下认识：１．震前形变能的演化过程是不稳定过程；２．形变能的突变发生在非平衡区；３．门源地震前后的跨断层地形变资料的计算结果与理论分析基本一致。 相似文献
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Wisam R. Muttashar 《Marine Georesources & Geotechnology》2020,38(8):896-910
AbstractThe mechanical response of a sediment to an applied stress is significantly affected by variations of material properties, state conditions, and stress states. These stress state and conditions are utilized to infer input parameters for advanced soil constitutive models. Parameters such as void ratio and effective stresses have been readily inferred from shear-wave velocities under low-strain conditions. Thus, this research aimed to develop a shear-wave velocity-based constitutive model within a critical state soil mechanics framework to predict the undrained triaxial behavior of fine-grained sediments. Laboratory tests were performed for sediment samples ranging from silt-predominant to clay-predominant sediments. As result, a new two-term power function was developed that determined mean effective stress as a function of shear-wave velocity. By virtue of this new power function, the Original Cam Clay and Modified Cam Clay critical state models were adapted to estimate the stress-strain behavior and stress paths under undrained conditions, in terms of shear velocity. In addition, correlations were developed using the state and material properties to predict the input model parameters. The developed correlations allow broad application of the proposed framework to different sediment types in which clay and silt are the dominant deposits. 相似文献
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The 1999 Chi-Chi, Taiwan, earthquake (Mw = 7.6) was one of the strongest earthquakes in recent years recorded by a large number of strong-motion devices. Though only
surface records are available, the obtained strong-motion database indicates the variety of ground responses in the near-fault
zones. In this study, accelerograms of the Chi-Chi earthquake were simulated at rock and soil sites, and models of soil behavior
were constructed at seven soil sites (TCU065, TCU072, TCU138, CHY026, CHY104, CHY074, and CHY015), for which parameters of
the soil profiles are known down to depths of at least ~70 m and at 24 other soil sites, for which parameters of the soil
profiles are known down to 30–40 m; all the sites were located within ~50 km from the fault. For reconstructing stresses and
strains in the soil layers, we used a method similar to that developed for the estimation of soil behavior based on vertical
array records. As input for the soil layers, acceleration time histories simulated by stochastic finite-fault modelling with
a prescribed slip distribution over the fault plane were taken. In spite of the largeness of the earthquake’s magnitude and
the proximity of the studied soil sites to the fault plane, the soil behavior at these sites was relatively simple, i.e.,
a fairly good agreement between the spectra of the observed and simulated accelerograms and between their waveforms was obtained
even in cases where a single stress-strain relation was used to describe the behavior of whole soil thickness down to ~70–80
m during strong motion. Obviously, this is due to homogeneity in the characteristics of soil layers in depth. At all the studied
sites, resonant phenomena in soil layers (down to ~40–60 m) and nonlinearity of soil response were the main factors defining
soil behavior. At TCU065, TCU110, TCU115, CHY101, CHY036, and CHY039 liquefaction phenomena occurred in the upper soil layers,
estimated strains achieved ~0.6–0.8%; at other stations, maximum strains in the soil layers were as high as 0.1–0.4%, according
to our estimates. Thus, valuable data on the in situ soil behavior during the Chi-Chi earthquake was obtained. Similarity in the behavior of similar soils during the 1995 Kobe,
2000 Tottori (Japan), and Chi-Chi (Taiwan) earthquakes was found, indicating the possibility of forecasting soil behavior
in future earthquakes. In the near-fault zones of the three earthquakes, “hard-type” soil behavior and resonant phenomena
in the upper surface layers prevail, both leading to high acceleration amplitudes on the surface. 相似文献
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Yun Zhang Yu-Qun Xue Ji-Chun Wu Shu-Jun Ye Zi-Xin Wei Qin-Fen Li Jun Yu 《Engineering Geology》2007,90(3-4):160-173
Excessive groundwater pumpage has caused regional cones of depression and severe land subsidence in the Southern Yangtse Delta, China. The characteristics of aquifer system compaction are complex because of the difference in the types, compositions and structures of the soils that the hydrostratigraphic units are composed of, and in the histories of groundwater level change the hydrostratigraphic units have experienced. Based on the data measured from extensometer groups and observation wells, the characteristics of deformation for individual hydrostratigraphic units are analyzed. The results show that different hydrostratigraphic units have different kinds of deformation and that an identical unit may also present different deformation characteristics, such as elasticity, elasto-plasticity, and visco-elasto-plasticity, at different sites of the cone of depression or in different periods. If the groundwater level rises continuously and remains constant later, the aquifers and the aquitard units that consist of hard clay primarily exhibit elastic behaviour, but the aquitard units that consist of soft clay deform plastically and by creep and exhibit visco-elasto-plastic behaviour. If the groundwater level falls but is much higher than the previous lowest value, aquifers and aquitards consisting of hard clay exhibit elasto-plastic behaviour. If the groundwater level falls below the previous lowest value, aquifers and aquitards consisting of hard clay deform plastically and by creep and exhibit visco-elasto-plastic behaviour. 相似文献
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P. W. J. Glover J. B. Gomez P. G. Meredith S. A. Boon P. R. Sammonds S. A. F. Murrell 《Surveys in Geophysics》1996,17(3):307-330
Measurement of complex electrical conductivity as a function of frequency is an extremely sensitive probe for changes in pore and crack volume, crack connectivity, and crack surface topography. Such measurements have been made as a function of pore fluid chemistry, hydrostatic confining pressure, as well as uniaxial and triaxial deformation. This paper will; (1) describe the effects of triaxial deformation on the complex electrical conductivity of saturated porous rocks, (2) use the electrical data to model the mechanical stress-strain behaviour, and (3) compare the modelled behaviour with the stress-strain behaviour measured during the deformation. Experimental conductivity data tracks how the rock undergoes compaction with progressive loss of crack volume, followed by dilatation due to new crack formation, growth of existing cracks, crack interlinkage, and finally failure, as axial strain is increased. We have used the complex electrical data to produce a direction-sensitive (anisotropic) crack damage parameter, and used it to calculate the effective Young's modulus by employing the models of Walsh and Bruner. Comparison of the synthetic stress-strain curves so produced, with the experimentally derived stress-strain curves shows good agreement, particularly for undrained tests. This modelling is an improvement on similar curves produced using isotropic crack damage parameters derived from acoustic emission data. The improvement is likely to be due to the directional sensitivity of the electrical conductivity measurement, and its ability to discriminate between the formation of isolated cracks, and those cracks that contribute to the inter-connected crack space i.e. those cracks upon which transport properties of the rock such as electrical conductivity, and mechanical properties depend most critically during triaxial deformation. 相似文献
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石灰岩、石蜡-松香-水泥粉混合物和环氧树脂等固体材料室温下的压缩变形实验表明,随着围压的加大和材料可塑性的增强,试件破坏形式由脆性转变为延性,在宏观结构上表现为从脆性单斜破裂、半脆性共轭破裂,到半延性和延性网状流动,以及延性均匀流动的转变.材料屈服后在应力-应变曲线上所出现的平缓段或应变硬化段对应着试件中的网络状或均匀塑性流动;随着应变的增大,当出现负坡或坡度减小现象时,则标志着试件内宏观破裂的贯通,在宏观破坏结构上往往表现为共轭流动网络与共轭破裂网络的重叠,前者网带近似正交,后者斜交.蠕变实验进一步表明,稳态蠕变幂次流动律的应力指数n 值的大小反映了试件不同的宏观流动结构:网络状流动,n 显著大于1,为非牛顿流;均匀流动,n 等于或近似于1,为牛顿流或近似牛顿流. 相似文献