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1.
真空预压技术加固海堤深厚软基原型试验研究 总被引：4，自引：0，他引：4
真空荷载提供了一种减少堤坝软土地基固结时间的选择. 本文开展了一个海堤全断面的试验及原型观测研究. 试验堤高5. 5 m, 22 m深且三角形布置的塑料排水板作为竖向排水通道, 现场布置了水平测斜和沉降仪等观测仪器, 埋设在不同地基深度的孔隙水压力计用来量测真空-堆载联合荷载下的地基中超静孔隙水压力的变化. 通过场地条件分析、高真空度维持和真空卸载, 得到了系统的沉降变形和孔隙水压力资料, 试验结果验证了真空-堆载联合预压加固海堤软土地基的效果. 相似文献
2.
林智勇 《福建工程学院学报》2016,(4):318-323
利用数值分析方法建立了软土地基模型,采用比奥固结理论,计算分析了真空预压下的软土地基流固耦合作用;并进一步分析了真空度损耗率、密封墙、塑料排水板打设深度等因素对软基加固效果的影响。分析结果表明:在抽真空早期,地表沉降增长很快,达到一定天数后,沉降值逐渐趋于稳定;真空负压沿深度、水平方向上损耗,在加固软土外围形成一个零孔隙水压力面;真空度损耗率、塑料排水板打设深度对真空预压加固软土的效果影响很大;侧向密封墙对加固区内土体影响不大,但其限制了真空负压的侧向传递,使影响区的地基沉降大幅减小。 相似文献
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采用真空联合堆载预压技术能通过排水固结提高地基承载力,和其他处理方法相比,能降低工程造价。结合工程实例,对加固原理、施工工艺、施工质量控制要点进行阐述,并通过监测和检测结果分析,为同类工程提供参考借鉴。 相似文献
4.
Due to large-scale dredging operations, a large amount of sludge is inevitably produced. Large areas of land are occupied when the dredged sludge is discarded in the disposal site as waste material. The sludge dewatering with aeration-vacuum (SDAV) method is suit for treating the sludge with high water content and high clay content in the disposal site. The water in the sludge can be discharged out. The volume of the sludge can be reduced quickly, and the recycling of the land can be accelerated by this method. Most importantly, this technique is an efficient way to deal with clogging problems when pumping water from high water content, high clay content dredged sludge. Vacuum degree range tests, the aeration rate range tests, and the influencing factors of sludge dewatering behavior tests were conducted with a self-developed SDAV model test device. Sludge samples were taken from the South-to-North Water Diversion East Line Project in Huai’an White-Horse Lake disposal site, Jiangsu Province, China. The optimal range of vacuum degree and aeration rate were obtained through the test results, and the mechanisms for how the two factors work and how they affect the sludge dewatering behavior were analyzed. The suitable vacuum degree range in SDAV is below 50 kPa, and the suitable aeration rate is about 1.0 m3/h. The low-vacuum degree contributes to reduce the ad-sorption effect of micro-channels on soil particles in filter material and to maintain the arch structures. Aeration has the effects of expansion, disturbance, changing Reynolds number, and dynamic sieve separating. The pump quantity of water per meter of filter tube (m) has different change rules as the vacuum degree changes under different aeration rates. The reason is that the formed arch structures’ conformation and permeability differ greatly under different combined-conditions of vacuum degree and aeration rate. The optimal combined-condition for dewatering the sludge is 35 kPa with 1.0 m3/h. 相似文献
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黄建华 《福建工程学院学报》2012,(3):222-229
针对海积饱和软土地基处理实际工程中采用搅拌桩复合地基和堆载预压排水固结两种方法,进行技术与经济的优化设计分析,预测饱和软土固结度及其沉降特征。通过工程现场监测数据和实际应用效果进行对比,验证理论分析成果和固结度计算以及沉降预测的有效性,结果表明,堆载预压和排水系统的有效结合,对处理沿海饱和软土地基具有良好效果,且经济有效。 相似文献
7.
在考虑软土超载预压后的次固结变形特性的基础上,推导出消除使用荷载作用下的主固结所需预压时间的公式.通过室内试验研究了不同超载量和不同超载预压时间对饱和软土次固结变形的影响,对排水固结法处理软土地基有一定的参考价值. 相似文献
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连云港海相软土具有含水量高、压缩性高、孔隙比高、强度低等特点,其工程性质较差,是该地区基础设计的重点和难点。结合某海相软土的加固处理工程,阐述了动力排水固结的加固机理,并对其加固效果进行了分析。检测结果显示,动力排水固结法处理连云港软粘土场地可以取得良好效果,其经验可供类似工程参考。 相似文献
9.
结合具体工程实例,对软基真空预压施工进行了阐述,提出了质量保证措施,并对施工监测数据进行分析,以完善施工工艺,从而提高真空预压处理水平,可为同类工程提供参考借鉴。 相似文献
10.
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
11.
为了研究粘土与加筋材料接触面之间的力学特性,及砂对粘土与筋带接触面力学特性的改善情况,采用直剪试验方法对粘土与聚丙烯土工带polypropylene在粘土不同含水量条件下进行了不同法向荷载作用的直剪试验,讨论了法向应力、含水量对高液限粘土与筋带之间剪切特性的影响;设计了筋带砂粘土层状布置体系的加筋土结构模型,并根据设计的模型进行直剪试验.试验结果表明:粘土与筋带接触面之间的剪切强度随着法向应力的增加呈非线性增长;接触面的摩擦系数随着含水量的增加而减小,接触面的粘聚力随含水量的增加先增大后减小,粘土与接触面之间存在一个最佳的含水量,这个值要比粘土压实的最佳含水量低2%左右;筋带砂粘土层状布置体系表明砂对粘土与筋带的剪切特性起到明显的改善作用. 相似文献
12.
回顾了基于CPTU测试成果确定粘土固结屈服应力和超固结比的方法,表明土的固结屈服应力和超固结比与CPTU测试参数之间不存在惟一的相关关系,仅仅针对某一地区的相关关系才是有效的.根据苏北里下河地区泻湖相沉积土的CPTU测试资料,对3种经验方法进行了比较.评价了固结屈服应力与CPTU测试参数现有经验关系的有效性,并且确定出适宜于里下河地区泻湖相沉积土的预测方法.结果表明:基于净锥尖阻力的相关关系比其他经验方法具有较高的精度,可以有效地预测该地区泻湖相沉积土的固结屈服应力和超固结比. 相似文献
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Cover-bearing-type bucket foundation for offshore wind turbines has been paid more and more attention due to its low cost and great bearing capacity. In order to ensure the cover-bearing mode, the muddy soil inside the bucket foundation should be reinforced by some soil consolidation methods, such as negative pressure and electro-osmosis. Firstly, tests were conducted to obtain the reasonable current density. Meanwhile, to improve the electro-osmotic speed and effectiveness, other factors such as intermittent power and layout of electrode, were also studied in the tests. Then, the soil reinforcing tests by negative pressure combined with electro-osmosis were performed for the muddy soil consolidation inside the bucket foundation. The results showed that soil reinforcement by negative pressure was quicker and more obvious during the early phase, and electro-osmotic method can affect more range of soil by rational arrangement of electrodes. Compared with negative pressure, the electro-osmotic method was a continuous and relatively slow process of reinforcement, which was complementary to the negative pressure method. The voltage value of electro-osmosis had little effect on the muddy soil reinforcement inside the bucket foundation, and 1.5 A was chosen as the most reasonable current value for scale model testing in the electro-osmotic method. 相似文献
15.
In this work, semi-analytical methods were used to solve the problem of 1-D consolidation of non-homogeneous soft clay with spatially varying coefficients of permeability and compressibility. The semi-analytical solution was programmed and then verified by comparison with the obtained analytical solution of a special case. Based on the results of some computations and comparisons with the 1-D homogeneous consolidation (by Terzaghi) and the 1-D non-linear consolidation theory (by Daviset al.) of soft clay, some diagrams were prepared and the relevant consolidation behavior of non-homogeneous soils, is discussed. It was shown that the result obtained differs greatly from Terzaghi’s theory and that of the non-linear consolidation theory when the coefficients of permeability and compressibility, vary greatly. 相似文献
16.
INTRODUCTION Since the development of the conventionalconsolidation theory by Terzaghi (1943) in 1923,many attempts have been made to present some solu-tions for the problems considering more realistic as-sumptions on the practical geotechnical engineering.Some efforts have been made to avoid limitation ofthe assumptions in the Terzaghi’s theory. During theconsolidation of soil, it is obvious that the coefficientof volume compressibility mv and the coefficient ofpermeability kv ar… 相似文献
17.
Numerous experiments have shown that the water flow in fine-grained soils can obey an exponential relationship at small gradients and a linear relationship when the hydraulic gradient exceeds a certain limit. Based on the non-Darcian flow described by exponent and threshold gradient, the theory of 1D consolidation is modified in this paper to consider a linear variation in the vertical total stress with depth and the effect of ramp loading. The numerical solutions were derived in detail by the finite difference method for excess pore water pressure and the average degree of consolidation. Finally, the influence of various parameters on consolidation behavior was investigated. The results show that the rate of consolidation is reduced when non-Darcian flow described by exponent and threshold gradient is adopted in the theory of 1D consolidation. As well the distribution of vertical total stress has a great influence on the dissipation of excess pore water pressure, either for pervious top and pervious bottom （PTPB） or for pervious top and impervious bottom （PTIB）. For the case of PTIB, the distribution of vertical total stress in a foundation has a great influence on the rate of consolidation; however, for the case of PTPB, the rate of consolidation is independent of the distribution of vertical total stress. The rate of consolidation is dependent on the ratio of the thickness of a soil layer to the equivalent head of the final average vertical total stress; the greater the value of this ratio, the slower the rate of consolidation. Finally, an increase in construction time reduces the consolidation rate of a foundation. Thus, consolidation behavior of 1D consolidation with non-Darcian flow has been thoroughly acquainted in this paper. 相似文献
18.
In a landfill, excessive tensile strains or failure of the liner system due to localized subsidence underneath the geosynthetic liner, is a concern in design and operation of the landfill. The localized subsidence can be commonly withstood by reinforcements such as geogrids. A total of nine model tests were carried out to study the influence of soil arching in overburden sandy soil on the geosynthetics and the interaction between the soil and the geosynthetics. The localized subsidence was modeled by a strip trapdoor under the geosynthetic reinforcements. The reinforcement includes several layers of polyvinylchlorid (PVC) membrane or both PVC membrane and a compacted clay layer. Test results show that the vertical soil pressure acting on the geosynthetics within the subsidence zone is strongly related to the deflection of the geosynthetics. The soil pressure acting on the deflected geosynthetics will decrease to a minimum value with respect to its deflection if the final deflection is large enough, and this minimum value is almost independent of the overburden height. Otherwise, the deflection of geosynthetics cannot result in a full degree of soil arching, and the soil pressure within the subsidence zone increases with the increase of overburden height. Deflections and strains of the geosynthetics obviously decrease with the increase of their tensile stiffness. The presence of a compacted clay layer buffer can therefore reduce both deflections and strains of the geosynthetics. Finally, a composite liner structure is recommended for landfills to withstand the localized subsidences. 相似文献
19.
Theone dimensionalinfinitesimalstrainconsolida tiontheorydevelopedbyTerzaghiassumedthattheper meabilityandcompressibilityoftheclayremainedcon stantduringconsolidationunderaparticularincrementofload[1] .So ,inpractice ,thetheorywasonlyapproxi matelysatisfying .Variousresearcheshavesoughttoex tendtheclassicaltheorytotakeaccountofthevariationofpermeabilityandcompressibilityduringconsolidationinoneormoreways .Thecompressibilityandcoefficientofpermeabilitywereassumedtobefunctionsofthede greeofsatur… 相似文献
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The mechanical characteristics of the weld joint were investigated by tensile test, microstructure test, and microhardness test. The welded tube NC bending tests were carried out to evaluate the weld on the formability of the QSTE340 welded tube. The results show that the wall thinning degree, cross-sectional deformation and springback angle increase significantly as the weld line is located on the outside of the bend compared with that located on the middle and inside, and the welded tubes produce nearly identical performance as the weld line is located on the middle and inside. The wall thickening degree decreases much as the weld line is located on the inside of the bend. So the welded tube can acquire good bending formability as the weld line is located in the region away from the outside of the bend. 相似文献