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1.
INTRODUCTION Adequate information on dynamic soil proper-ties, especially dynamic shear modulus and dampingratio, is essential for accurate computations of groundresponse and soil-structure interaction problems.Many experimental investigations carried out onsandy soils through resonant column test or improvedcyclic triaxial test in early studies (Hardin and Richart1963; Hardin and Black, 1968; Drnevich and Richart,1970; Seed and Idriss, 1971; Kokusho, 1980) showedthat the small … 相似文献
2.
There exists a critical cyclic stress ratio when sand or clay is subjected to cyclic loading. It is an index distinguishing stable state or failure state. The soil static and dynamic universal triaxial and torsional shear apparatus developed by Dalian University of Technology in China was employed to perform different types of tests on saturated soft marine clay in the Yangtze estuary. Undisturbed samples were subjected to undrained cyclic vertical and torsional coupling shear and cyclic torsional shear after three-directional anisotropic consolidation with different initial consolidation parameters. The effects of initial orientation angle of major principal stress, initial ratio of deviatoric stress, initial coefficient of intermediate principal stress and stress mode of cyclic shear on the critical cyclic stress ratio were investigated. It is found that the critical cyclic stress ratio decreases significantly with increasing initial orientation angle of major principal stress and initial ratio of deviatoric stress. Compared with the effects of the initial orientation angle of major principal stress and initial ratio of deviatoric stress, the effect of initial coefficient of intermediate principal stress is less evident. Under the same consolidation condition, the critical cyclic stress ratio from the cyclic coupling shear test is lower than that from the cyclic torsional shear test, indicating that the stress mode of cyclic shear has an obvious effect on the critical cyclic stress ratio. The main reason is that the continuous rotation in principal stress directions during cyclic coupling shear damages the original structure of soil more than the cyclic torsional shear does. 相似文献
3.
Constitutive model of saturated soft clay with cyclic loads under unconsolidated undrained condition
An equivalent visco-elastic model of saturated soft clay was studied under unconsolidated undrained (UU) condition, which can be used to evaluate the stability of ocean foundation. Cyclic triaxial compression and extension tests were conducted to study the parameters of the model. Results showed that the relationships of the damping ratio and the octahedral shear modulus with the octahedral cyclic shear strain were nearly unique, when the initial octahedral shear stress ratios of specimens were equal to 0.3, 0.5 and 0.7. The relationships of the damping ratio and the octahedral shear modulus with the octahedral cyclic shear strain determined from the cyclic triaxial compression tests were basically the same as those determined from the cyclic triaxial extension tests. Furthermore, the relationships were not related to the initial stress condition, the test stress state and the octahedral cyclic shear stress ratio. The relationships determined from the cyclic triaxial tests under no deviatoric stress were basically the same as those determined from the cyclic triaxial tests under deviatoric stress. The change of the octahedral cyclic accumulative strain with the number of cycles was unique under different tests stress states. An equivalent visco-elastic constitutive model of saturated soft clay under UU condition was initially established. 相似文献
4.
Soil liquefaction can cause disastrous consequences to buildings and human lives. Regular countermeasures against soil liquefaction are often overly expensive for normal buildings and structures. This could be the major reason that liquefaction induced damage is still widely encountered in large- and mid-size earthquakes in recent years. In this paper, a new method for the mitigation of soil liquefaction using the microbially induced soil desaturation is proposed and tested. The desaturation effect in soil is achieved by the generation of nitrogen gas produced from the microbial denitrification process. Some major issues related to this method are experimentally investigated. These include soil desaturation procedures, shapes and distribution of gas bubbles in soil, mechanical responses and liquefaction resistance of desaturated soils, and stability of gas in soils. The desaturation treatment of soils is made simply by introducing denitrifying bacteria and a desaturation solution into soil pores by mixing, flushing, or injection. The degree of saturation can be reduced as the microbial reaction proceeds. Experimental results show that the final degree of saturation is related to the initial nitrate concentration added to the soil: the higher the concentration of nitrate in the desaturation solution, the lower the degree of saturation that can be achieved. The existence of gas bubbles in soil is evidenced by computer tomography (CT) technology. The CT images reveal that gas is in the form of small pockets which has a size a little larger than the mean size of sand grains. It is shown in the shaking table tests that microbially induced desaturation can effectively improve the liquefaction resistance of soil by showing a much lower pore pressure generation, much smaller volumetric strain, and much smaller settlement of the structure in desaturated soil, as compared with those in saturated soil. Triaxial consolidated undrained tests reveal that the desaturation treatment of soil can improve the undrained shear strength of loose sand. The stability of gas is tested under hydrostatic and water flow conditions. The gas phase is stable under the hydrostatic condition, but unstable under water flow conditions. So measures ought to be taken to prevent steady flow in practice. 相似文献
5.
The flat dilatometer test (DMT) has the potential to be a useful tool in the evaluation of liquefaction potential of soils.
In practice, it is necessary to carefully examine existing DMT-based methods for evaluating liquefaction potential. We conducted
the DMT and cone penetration test (CPT) in high liquefaction potential areas to examine the existing DMT-based methods for
liquefaction potential evaluation. Specifically, the DMT and CPT were conducted side-by-side at each of six in-situ sites,
and thus it is feasible to utilize those test results to validate the existing DMT-based methods. The DMT parameter, horizontal
stress index (K
D), is used as an indicator for estimating liquefaction resistance of soils in terms of cyclic resistance ratio (CRR). The
analysis results revealed that the existing K
D-based liquefaction evaluation methods would overestimate the CRR of soils, which leads to overestimation of the factor of
safety against liquefaction. Also, the estimations of DMT-K
D values by using the CPT-q
c as well as the correlation between DMT-K
D and CPT-q
c proposed by the previous studies would be significantly smaller than field measurements. The results reflected that further
validation of the existing DMT-based methods for liquefaction evaluation is desirable. 相似文献
6.
FOR THE GEO一TEEHNIEAL DESI，PARAMETERS OF 5011，EOMPARISON OF SEISMIE RESPONSES BASED ON DIFFERENT THE UNEVEN DISTRIBUTION OF THE DIFFERENT KINDS OF 5011 METHODS TO EVALUATE THE 5011 FUNETIONS.IN ADDITION， AND SAMPLING LOCATIONS DURING EXPLORATION AND I… 相似文献
7.
Failure criterion of saturated soft clay is studied under cyclic loads through different experiments. A large number of cyclic torsional shear and cyclic triaxial tests on saturated soft clay under unconsolidated undrained condition are conducted. From the test result analysis, it is seen that the failure of saturated soft clay under static and cyclic loads satisfies Mises criterion. The result from different test stress states is not related to the test stress states or confining pressures. It can be applied in general stress states. Then according to the Mises criterion, the equivalent relationship on failure moment between the test stress state and the general stress state can be established. So the cyclic mechanics characteristics of saturated soft clay at failure moment are clarified in this paper. Furthermore, a theory basis is provided for using pseudo-static elasto-plastic cyclic strength model to evaluate cyclic bearing capacity. 相似文献
8.
The bender element testing features its in-plane directivity, which allows using bender elements to measure the shear wave velocities in a wider range of in-plane configurations besides the standard tip-to-tip alignment. This paper proposed a novel bender element testing technique for measuring the horizontal shear wave velocity of soils, where the bender elements are surface- mounted and the axes of the source and receiver elements are parallel to each other. The preliminary tests performed on model ground of silica sand showed that, by properly determining the travel distance and time of the shear waves, the surface-mounted bender elements can perform as accurately as the conventional ＂tip-to-tip＂ configuration. Potentially, the present system provides a promising nondestructive tool for characterizing geomaterials and site conditions both in laboratory and in the fields. 相似文献
9.
设计了4种不同水胶比(0.52、0.48、0.44、0.40)自密实混凝土试件(N1、N2、N3、N4),分别在不同养护龄期(7、14、28、56、84、112 d)时进行超声波速与抗压强度的测试,得出强度与波速随龄期增长的变化规律,并根据其变化规律作回归分析,获得合适龄期内两者的函数关系。结果表明:试件抗压强度随养护龄期延长而增加,增长速率逐渐下降;在一定龄期内,强度与波速存在密切的内在联系,又因不同水胶比的试件波速增长速率不同,故回归方程不同;水胶比为0.52的自密实混凝土以幂函数拟合性最好,水胶比为0.48、0.40自密实混凝土则以指数函数最优,而对于水胶比为0.44的自密实混凝土,线性函数最佳;建立无损模拟曲线方程,可为预测适用本地区低水胶比自密实混凝土强度提供理论支持,也为检测加固工程中自密实混凝土质量问题提供了数据支撑。 相似文献
10.
In this paper we propose a degradation model to describe the damage-dependent behavior of saturated soft clay under cyclic loading, which is then applied to the analysis of a caisson breakwater. The degree of damage and remolding of soft clay is quantified by a damage parameter related to the accumulated plastic deviatoric strain. Through the correlation between the maximum pore pressure and the undrained strength of soft clay, we obtain a damage-dependent degradation model that employs the post-cyclic undrained strength degradation coefficient in terms of the cyclic stress ratio and the number of cycles. Based on the Tresca yield criterion, the degradation model of undrained strength of soft clay is numerically implemented in the user interface USDFLD of ABAQUS. The performance of this model is verified by a comparison between numerical results (finite element method) and experimental data (cyclic triaxial test). The model is applied to the numerical simulation of a caisson breakwater resting on a partially sand-filled soft clay seabed under cyclic wave loading. The cyclic stress distribution, pore pressure development, and strength degradation of the seabed soil are presented to illustrate the applicability and efficiency of the model in the analysis of the interaction between offshore structures and soft ground. 相似文献
11.
以宁德乡土树种柳杉为原料,聚乙二醇为液化剂,在浓硫酸和磷酸的混酸催化作用下,进行了木材液化试验.通过单因素试验,以残渣率为指标探讨了液化反应温度、反应时间、液比及催化剂用量与配比对柳杉液化反应的影响.结果表明,在反应温度160℃、反应时间120min、液比4：1、催化剂用量6%以及硫酸/磷酸体积比2：1的条件下,柳杉液化残渣率为9.5%. 相似文献
12.
张红敏 《山西广播电视大学学报》2003,8(1):73-74
通过对不同自由场地液化势估计的方法和公式进行总结和比较 ,发现剪切波速比其它波的波速更能反映地基岩土层的工作性能 ,现已为全国地基勘察规范所采用 相似文献
13.
杨科峰 《杨凌职业技术学院学报》2009,8(3):1-3
现行建筑抗震设计规范采用标准贯入试验判别砂土液化,在实际工作中,愈是液化场地地层愈是松散、易塌孔,很难清底,应用标准贯人试验很难取得饱和砂土的贯入试验准确数据,通过有关理论的推导计算和实际互作的试验对比。认为应用园锥动力触探试验与标准贯入试验是有一定关联,对判别饱和砂土液化是具一定的参考意义。 相似文献
14.
Seismic ductility of very-high-strength-concrete short columns subject to combined axial loading and cyclic lateral loading 总被引：1，自引：0，他引：1
JIANG Rui JIA Jin-qing XU Shi-lang 《重庆大学学报(英文版)》2007,6(3):205-212
The seismic ductility of reinforced very-high-strength-concrete (VHSC) short columns was studied by combinatively applying axial load and low cyclic lateral load on specimens to simulate seismic impact. Twelve specimens with concrete compressive strength ranging from 95.6 MPa to 118.6 MPa and a shear-span ratio of 2.0 were tested for shear failure pattern and fear force-displacement hysteretic responses. Combinative application of axial load and low cyclic lateral load to VHSC short columns incurs shear failure. The displacement ductility is much smaller when the axial load ratio is larger;whereas a larger stirrup ratio is accompanied with a better displacement ductility. The relationship of displacement ductility factor, μ?, with stirrup characteristic value, λv, and test axial load ratio, nt, is μ?=(1 8λv)/(0.33 nt). By this relationship and relevant codes for aseismatic design, the axial load ratio limits for aseismatic design of reinforced VHSC (C95 to C100) short columns for frame construction are respectively 0.5, 0.6, and 0.7 for seismic classes I, II, and Ⅲ;corresponding minimum characteristic values of stirrups are calculated according to the required characteristic values of at least 1.273 times of experimental results. These data are very useful to aseismatic engineering. 相似文献
15.
Monotonic triaxial experiments to evaluate steady-state and liquefaction susceptibility of Babolsar sand 总被引：1，自引：0，他引：1
In this study, drained and undrained triaxial tests under isotropic and anisotropic consolidations were conducted on reconstituted samples of Babolsar sand, which underlies a densely populated, seismic region of the southern coast of the Caspian Sea, Mazandaran, Iran. It was demonstrated that the sand experienced all possible states of liquefiable soil： flow failure, limited flow, and dilation. The steady-state and flow liquefaction lines of this sand were presented and compared with previously tested sands. It is shown that the initial stress anisotropy can affect the potential of volume change and pore pressure generation. The steady-state line （SSL）, however, remains identical for the isotropically and anisotropically consolidated specimens under drained and undrained conditions. The tests data were then analyzed in order to investigate the liquefaction susceptibility of this sand in terms of parameters such as the state parameter, relative state parameter index, and lateral earth pressure ratio at failure. 相似文献
16.
Influence of water saturation on propagation of elastic waves in transversely isotropic nearly saturated soil 总被引：1，自引：0，他引：1
INTRODUCTIONIthaslongbeenrecognizedthatcompression alwavespropagationinsaturatedsoilsisstronglyaffectedbythewaterfillingtheintersticesofthesoilgrains.HardinandRichart(1 963 )appliedthetwo phasetheoryofBiot(1 956)andstudiedtheinfluenceoftheconfiningpressur… 相似文献
17.
磁场作用下的磁性流体行波泵研究是行波泵设计的基础。通过分析了行波磁场作用下的磁性流体的运动方程,从而进一步推导了行波磁场作用下的磁性流体的速度方程、旋转速度方程和单位时间内的流量方程,并通过实验进行了验证。研究表明：行波磁场作用下的磁性流体会产生流动现象;行波磁场作用下的磁性流体流量与磁极旋转的角度有直接关系,磁极旋转的角度越大,其流量也越多;行波磁场的强弱对磁性流体流量也会产生影响,磁场越强,其流量越大;行波磁场的频率只能影响磁性流体的流速,对流量不产生任何直接影响。 相似文献
18.
1 Ｉｎｔｒｏｄｕｃｔｉｏｎ Ｍｏｄｅｌｉｎｇｏｆｓｏｉｌｂｅｈａｖｉｏｕｒｐｌａｙｓａｎｉｍｐｏｒｔａｎｔｒｏｌｅｉｎｄｅａｌｉｎｇｗｉｔｈｐｒｏｂｌｅｍｓｒｅｌａｔｅｄｔｏｓｏｉｌｍｅｃｈａｎｉｃｓａｎｄｆｏｕｎｄａｔｉｏｎｅｎｇｉｎｅｅｒｉｎｇ .Ｏｖｅｒｔｈｅｐａｓｔｆｏｕｒｄｅｃａｄｅｓ ,ｍａｎｙｒｅｓｅａｒｃｈｅｒｓｈａｖｅｄｅｖｏｔｅｄｅｎｏｒｍｏｕｓｅｆｆｏｒｔｓｔｏｆｏｒｅｃａｓｔｉｎｇｔｈｅｌｉｑｕｅｆａｃｔｉｏｎｏｆｓａｔｕｒａｔｅｄｓｏｉｌｕｎｄｅｒｖａｒｉｏｕｓａｓｓｕｍ… 相似文献
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面波法与单孔检层法波速测试的工程应用 总被引：3，自引：0，他引：3
简述了面波法与单孔法等波速测试方法的工作原理、现场施测技术以及数据处理和资料分析过程.以工程实例说明了波速测试技术在岩土工程勘察设计中的应用及其效果.最后就勘探工作的总体安排及其原位测试方法的选择进行了探讨. 相似文献