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An experimental investigation was carried out on the reconstituted Tunis soft soil (TSS) that was extracted from the centre of Tunis City at 35-m depth. Three series of consolidation tests were performed on TSS specimens. The first series included consolidation tests by preload. In the second series, vacuum consolidation tests were performed. The third series comprised a vacuum consolidation test combined with the preload. Excess pore water pressure and settlement were measured during the consolidation tests. Experimental results showed that for the same magnitude of preload and the vacuum pressure of 4, 8, 16 and 30 kPa, the settlement caused by the vacuum pressure is lower than that generated by the preload, while the settlements generated by preloads of 60 and 100 kPa are slightly lower than those caused by vacuum pressure of 60 and 100 kPa. A rapid dissipation of recorded excess pore water pressure around the geodrain was observed compared to that measured close to the cell border. 相似文献
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A comprehensive analysis of maintaining stability by model homogeneous and stratified slopes, with possible surcharge loading, is carried out within the article. Calculations are performed by the Swedish method of Fellenius under the assumption of a cylindrical slip surface passing through the slope foot. Proposals for searching for the reach of the break-off wedge of a potential slip surface are put forward. An analysis of the effect of surcharge load location on general slope stability is also made, providing the capability to determine the safe distance of positioning of an excavator on the surcharge of a non-encased excavation. 相似文献
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Seismic stability of retaining walls with surcharge 总被引：6，自引：0，他引：6
The use of pseudo-static methods for the computation of soil thrust acting on retaining walls under seismic condition is well established in the design of such structures. Although different methods, based on the limited displacement concept, have been developed in the last 20 years, the most common design method is still the method derived from the theory developed by Mononobe and Okabe. However, the Mononobe–Okabe method presents a basic shortcoming: the solution is based on the limit equilibrium of the soil wedge without taking into account the presence of the wall. In the paper a new solution based on the pseudo-static equilibrium of the soil–wall system is presented. The developed solution takes into account the effect of the presence of the wall and it is applied to soil–wall systems with surcharged backfills. Formulas are provided to calculate directly the yield acceleration and the inclination of the failure surface. The effect of the intensity of the surcharge and of its distance from the wall is investigated and the results are compared to those obtained in the case of soil–wall systems without surcharge. 相似文献
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The life extension of ageing oil wells is becoming an ever more crucial part of an operator's activities in recent years, mainly due to slumping oil price which discourages new exploration and the potential extended operation of some older fields with sufficient producing capacity still remaining. The conductor forms one of the primary structural components of wells and its deterioration over time warrants immediate integrity assessment and rehabilitation plans. The construction residual loading or preloads on the conductor are calculated as per standard guidelines and by analytical means during its design and installation phase, but may not be realistic when assessing aged conductors, due to the high levels of over-conservatism built in to address the various uncertainties during the well drilling phase, hence a more practical means of evaluating this residual load is required in carrying out the integrity assessments. This article presents the novel use of ultrasonic based non-destructive technique (NDT) to measure the conductor preload by observing the travel time of the longitudinal critical refracted (LCR) waves and employing the acoustoelastic method to determine the structural stresses. The measurement of the time of flight (TOF) of this wave component is evaluated from the signals measurement under a range of preload stresses induced into the specimen, and the acoustoelastic calibration curve is obtained as a result, for various section geometries and dimensions. Numerical analyses are also carried out to correlate and validate the magnitude order of the acoustoelastic constant of typical conductor steel grade (grade-B). These are in good agreement with each other and can be a very reliable tool for the on-site preload measurements during oil well integrity assessment. This measurement of conductor preload results in minimising any associated uncertainties, assumptions and the corresponding over-conservatisms carried over from the design stage, hence streamlining the repair and rehabilitation strategies to the most critical well-conductor groups in the field, thus significantly reducing the costs and resources for operators in extending life of aged wells. 相似文献
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Slope stability analysis generally considers a homogeneous slope composed of either soil or rock. There is no definitive criterion to distinguish homogeneous and heterogeneous slopes. This paper presents five model tests on two-layered slopes with different interface subjected to surcharge load. Numerical simulations were performed to capture the behaviors observed. Given the satisfactory reproduction of the model tests, a parametric study was then conducted to investigate the impact of the interface, slope angle and strength parameters. Finally, a set of criteria based on the relative cohesion ratio was proposed to characterize a distinct change in the nature of the slope. 相似文献
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单向压缩状态下上海地区软土的蠕变变形与次固结特 性研究 总被引：1，自引：0，他引：1
基于上海地区原状软土的一维固结试验,讨论了在不同加荷比、加荷速率及超载预压情况下软土的蠕变变形特性和次固结特性。试验结果表明:蠕变变形随应力水平、加荷速率的增大而增大。相同应力水平下,加荷比较大的土样蠕变变形较小。蠕变变形为非线性,随着应力水平的增加,蠕变变形从粘弹性到粘塑性转变,加荷比较大时,这种转变更明显。对试验结果进行曲线拟和,确定Metchell一维经验模型参数,拟和曲线与试验结果吻合较好。通过对次固结阶段试验数据的线性拟合可知,对于正常固结土,次固结系数Ca值受应力水平和加荷比的影响不大,而与加荷速率密切相关,加荷速率较大时,Ca值随荷载的增大急剧增大后略有降低。超载预压可有效减小次固结系数,从而有利于减小工后次固结沉降。 相似文献
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Effect of Surcharge on the Stability of Anchored Rock Slope with Water Filled Tension Crack under Seismic Loading Condition 总被引：1，自引：0，他引：1
S. K. Shukla S. Khandelwal V. N. Verma N. Sivakugan 《Geotechnical and Geological Engineering》2009,27(4):529-538
In this paper, an analytical expression is derived for the factor of safety of the rock slope incorporating most of the practically
occurring destabilizing forces as well as the external stabilizing force through an anchoring system. The slope stability
is analyzed as a two-dimensional problem, considering a slice of unit thickness through the slope and assuming negligible
resistance to sliding at the lateral boundaries of the sliding block. A detailed parametric study is presented to investigate
the effect of surcharge on the stability of the rock slope for practical ranges of governing parameters such as inclination
of the slope face, inclination of the failure plane, depth of tension crack, depth of water in tension crack, shear strength
parameters of the material at the failure plane, unit weight of rock, stabilizing force and its inclination, and seismic load.
For the range of parameters considered in the present study, it is found that the factor of safety of the rock slope decreases
with increase in surcharge; the rate of decrease being relatively higher for lower values of surcharge. It is also observed
that for a specific surcharge, the factor of safety depends significantly on all other parameters, except for unit weight
of rock and higher values of inclination of stabilizing force to the normal at the failure plane. For any combination of these
variables, the surcharge plays a vital role in the stability. A perfectly stable slope at relatively low surcharge can become
unsafe with the increase in surcharge. The deterioration in the stability can be quite rapid, depending on the combination
of the factors under consideration. The analysis and the general expression proposed herein can be used to carry out a quantitative
assessment of the stability of the rock slopes. 相似文献