共查询到18条相似文献，搜索用时 312 毫秒
1.
针对土工合成材料界面特性试验易受试验装置影响的特点,采用大型叠环式剪切仪进行土工织物与砂土的界面剪切试验。对比砂土本身、土工织物与砂土的两种剪切试验结果发现,土工织物-砂土剪切引起的叠环位移较小;叠环的水平位移变化规律与土体的剪胀性具有密切联系,土工织物限制了下剪切盒内土颗粒的运动,对达到峰值强度时的土体剪胀也具有抑制作用。由试验结果可知,筋-土界面的剪切带远小于剪切的影响范围,土工织物在界面剪切中的作用不能仅通过剪切带反映,还应考虑土工织物的屏蔽作用和对于土体剪切带形成的影响。 相似文献
2.
以黄骅港防波堤工程为依托,对有、无土工织物加筋垫层及不同织物加筋条件下堤坝和软土地基的变形与稳定进行了离心模型试验对比研究。得到了地基土体的竖向与水平位移分布规律以及孔隙水压力的消散特性。研究表明：土工织物加筋垫层的加筋机理源于其对土体的侧限效果,铺设土工织物后能有效地减小地基的沉降,并能够限制浅层土体的侧向变形;为使土工织物的加筋效果能够得以充分发挥,要求织物的强度及模量要与垫层的界面强度相匹配。 相似文献
3.
土工织物加筋技术在工程中得到了广泛的应用,取得了良好的加固效果。但对于土工织物加筋机制尚缺乏明确和统一地认识,加筋理论研究落后于工程实践。为此,进行了坡顶加载条件下土工织物加固黏性土坡和素土边坡的离心模型试验,记录和再现了素土边坡和加筋土坡在坡顶加载条件下的变形破坏过程。主要基于变形分析探讨了黏性土坡在土工织物简单加固条件下的加固效果和加筋机制。结果表明,土工织物加筋可以有效地提高黏性土坡的极限承载力,加筋带的存在改变了土体的位移场,扩大了坡顶加载的影响区域,加筋后滑裂面明显后移。加筋带对土体的局部作用和作用范围,随着土体变形的增大而增大和扩展 相似文献
4.
土工袋能够有效地约束袋内土体,具有良好的滤水保土作用,可以用于地基抗液化,但土工袋抗液化性能尚未有系统及深入的研究。开展了一系列小振动台试验,验证土工袋垫层的抗液化效果,研究了振动加速度、土工袋层数和排列方式对抗液化性能的影响。结果表明：土工袋具有良好的抗液化效果,袋内土体的超静孔压比小于同深度处周围的土体;土工袋垫层的排水性能是在土工袋本身具有良好透水性的基础上,孔隙水会沿着土工袋与土体的界面以及袋间的空隙排出;相较于不透水刚性垫层,振动过程中土工袋垫层表面基本保持水平,发挥出较好的变形协调性;土工袋层数增加及交错式排列对抗液化效果有利。 相似文献
5.
研究了波动水流对海堤织物滤层的水力要素及过滤机理。粒径小于0.6 mm颗粒间存在粘着力;同时,由于滤层和堤体的渗透流速不一致,则堤体界面的土颗粒将受水流剪应力的作用。在分析了使土颗粒发生变形的水流剪应力、变形土体周壁的屈服应力和波浪压力等后,根据平衡原理,建立了织物滤层的保土性准则。 相似文献
6.
在考虑土的固结和土体的非线性应力应变关系的基础上,利用非线性有限元数值方法对土工织物加筋柔性台背路堤的受力性状和破坏机理进行了分析。分析结果表明,将铺有土工合成材料的桥台路堤,看作由土体、土工合成材料、土体-土工合成材料界面组成的、独立的平面应变三层连续体系,进行数值计算是行之有效的。计算结果显示,土工织物加筋可以有效减少桥台路堤50%的均匀沉降和66%的非均匀沉降,并能增加台背路堤的稳定性。现场监测表明,本文采用的数值模拟方法与实际工程具有一致性。 相似文献
7.
提出了一种新的岩土材料微细结构光学图像测量方法。实现了常规土工三轴实验与岩土材料微细结构的联合测试,获得了土体在荷载作用过程中微细结构变化清晰的图像序列,不仅可以定量研究土体在荷载作用下微结构的变化情况,还可利用数字图像相关技术对微细结构图像序列进行相关分析,得出土颗粒在荷载作用下的微观位移场,为建立土体合理的本构关系模型提供试验依据。 相似文献
8.
采用有限元方法对土工织物加固软弱地基路堤的力学机理进行了研究.通过比较路基加筋和未加筋两种情况研究了土工织物的加固机理,结果表明土工织物对于提高路堤填筑高度、减少路堤侧向位移、均化路堤沉降以及加速超孔隙水压力消散有显著的效果.加筋路堤中土工织物的轴力受填筑高度、超孔压消散速度和接触面系数等因素的影响,路堤填筑高度和施工进度的控制有利于土工织物抗拉强度的发挥.对路堤安全系数的研究分析表明传统的极限平衡法验算路堤稳定性偏于保守,采用有限元方法能较好地反映土工织物的加筋作用,可以优化工程设计. 相似文献
9.
运用弹塑性理论和有限元法,采取试算分析的办法,确立了选取计算城范围和确定边界条件的原则,在此基础上,探讨了土工织物的水平向加筋,得到了如下 结论：由土工我成的水平向加筋体能均化地基浅部应力,消减路堤坡脚处的剪应力集中现象,且能隔离上,下土体,从而防止路堤发生“由表及里”的渐进性破坏。 相似文献
10.
采用非线性有限元方法,对土工织物能否减少软弱路基的竖向沉降量进行了探讨。对比计算表明:当路堤宽度较小时,土工织物的加筋作用使路堤体内的竖向位移速度场减小,从而可使竖向沉降量减少12%~16%,并可使路堤的稳定性提高达20%;当构筑物宽度较大时,土工织物对构筑物体内竖向沉降量的影响不大,即土工织物的加筋作用存在尺寸效应。因此,工程实际中应根据具体情况判断是否选用土工织物来改善构筑物的竖向沉降。分析表明:传统的极限平衡法来考察土工织物加固软土工程的稳定性时,由于存在诸多假定而导致该方法不能很好的反映土工织物与土之间的变形协调关系。故应发展非线性有限元方法来模拟土工织物与土之间的相互作用关系。 相似文献
11.
Geotextile filters are rapidly replacing graded granular filters as the standard of practice in geotechnical design. The objective
of the present study is to predict the behavior of the geotextile filter for the locally (Roorkee—India) available soils using
three different geotextiles (two nonwoven and one woven). Nonwoven geotextiles are commonly used in filtration applications.
This paper evaluates the long-term performance of two needle-punched nonwoven geotextiles and one woven geotextile. Filtration
tests on soil–geotextile filter systems were conducted in the laboratory in order to evaluate the filtration and clogging
behavior. Laboratory test program, include evaluation of performance of two different nonwoven and one woven geotextile filters
in combination with locally available Solani River Sand and Clayey Soil. The paper describes the concept and details of the
Fine Fraction Filtration (F 3) test and presents data on three different geotextiles, which were evaluated using three different soil types. It is deduced
that in all filtration applications, the non-woven geotextile would perform better than the woven geotextile. 相似文献
12.
对压力作用下的部分堵塞无纺织物进行了室内试验,表明有土颗粒进入的织物压缩性和渗透性都降低,提出织物滤层的等效孔径折减系数RF,并建议用于贴坡排水时RF 取1.5～2.5。织物无堵塞压力条件下,Giroud（1996年）提出的公式对织物渗透系数有满意的预测值。在压力作用下对比分析了部分堵塞织物Giroud法和等效孔隙率法的渗透系数预测值,也与实测渗透系数值进行了比较,表明提出的等效孔隙率法能较好地预测渗透系数。 相似文献
13.
在土工织物反滤排水工程中,织物滤层在应力、渗流实际工况下的反滤特性是保证工程安全的关键问题。为揭示无纺土工织物过滤黏土的反滤机制,采用自主研制的可施加法向压应力的梯度比渗透仪试验装置测定黏土−无纺土工织物滤层体系的渗透系数kT、各分层土的渗透系数kj、梯度比RG和试验前后土工织物试样的质量变化情况,研究在不同水力梯度、应力水平下无纺土工织物过滤黏土的反滤特性。结果表明：黏土−无纺土工织物滤层体系的渗透系数kT和梯度比RG随着时间的增加而减小,并最终趋于一个稳定值;增大水力梯度可以改善黏土−无纺土工织物滤层的透水性,增加应力水平会降低土工织物滤层的透水性且提高其保土性;渗流作用下,被保护土层表现为靠近无纺土工织物的底层土渗透系数最小,远离无纺土工织物的最上层土的渗透系数最大;堵塞系数与黏土−无纺土工织物滤层体系的渗透系数kT、梯度比RG存在内在的关系,在特定的应力−渗流作用下可能存在一个临界堵塞系数,大于该值时将造成无纺土工织物滤层的反滤失效。 相似文献
14.
无纺土工织物作为一种反滤材料,在工程中常受土体作用产生平面双轴拉应变,导致织物孔径变化。基于无纺织物空间网络孔径模型,改进Rawal公式中织物孔径结构总层数的算法,并提出等双轴拉伸下织物孔径分布曲线的解析解。利用自主研发的双轴拉伸仪,将两种针刺无纺织物等双轴拉伸至应变为3%、5%、10%,采用应变控制下的干筛法,进行织物孔径分布曲线测试。将解析解与试验结果进行对比分析,解析解孔径值偏大,所得解析曲线与测试曲线对于较薄织物吻合更好。研究结果表明,随着双轴拉应变的增加,无纺织物孔径增大,其特征孔径O95、O50、O30都近似与拉伸应变呈线性变化关系。 相似文献
15.
The impact of erosion control geotextiles on the surface runoff from slopes is quite variable and depends strongly on site-specific conditions (soil characteristics, slope morphology, climate, etc.), as has been shown in several earlier studies. In addition, little is known about the proportion of runoff reduction that is caused by the geotextile and the proportion that is caused by soil characteristics. To shed more light on this issue, an experiment was carried out to test the impact of 500 g m ?2 jute nets (J500) and 400 g m ?2; 700 g m ?2 coir nets (C400, C700) on the surface runoff from simulated rainfall of four different intensities ( I 1 = 18.7; I 2 = 27.2; I 3 = 53.6; I 4 = 90.5 mm h ?1). Data on runoff volume, peak discharge and time to peak discharge were collected from 40 simulated rainfall events. An impermeable “no-soil” subgrade was used to examine the impact of the geotextile on runoff without any influence of soil. All tested geotextiles significantly reduced runoff (volume, peak discharge) at all rainfall intensities, with the exception of C400 and C700 during simulated rainfall intensity I 4. J500 seemed to have the most effective runoff reduction performance at all rainfall intensities. In general, as the rainfall intensity increased, the effectiveness of the geotextiles decreased. Interesting behaviour was observed for J500 under simulated rainfall intensity I 4—the effectiveness of the geotextile increased with the duration of the rainfall. 相似文献
16.
In most marine reclamation projects, sand fill is placed directly on soft marine seabed soils. The sand particles can easily penetrate into the soft marine soils, and the soft soil can also move into the pore spaces inside the sand at the initial contact interface between the sand and the soft marine soil. In this case, the permeability and the volume of the sand above the initial surface are reduced. To avoid this problem, a geotextile separator is often placed on the surface of the soft marine soils before placing the sand. In this study, a two-dimensional physical model is utilized to study the geotextile separator effects. The initial conditions of a clayey soil, sand fill, and surcharge loading were kept the same in the physical model test with the only difference being that a geotextile separator was either placed on the clay surface or omitted. The settlements of the initial interface were recorded and compared for the two cases without or with the geotextile separator. The particle size distribution of the soils taken across the interface zone for different time durations was then measured, analyzed, and compared. Based on an analysis of the results, the sand percolation depth was 40 mm and fine particle suffusion was apparent when the sand was placed directly on the marine slurry surface without a geotextile separator. However, when a geotextile separator was used sand percolation was avoided, and the fine particle suffusion was effectively diminished. A relative fine particle fraction is defined to illustrate the migration of fine particles from the clay to the sand soils. The fine particle percentages of the Hong Kong Marine Deposits–sand mixtures were calculated for the cases with and without a geotextile separator using an empirical formula and micromechanical modeling to obtain a better understanding of the effects of geotextile separators in practice. 相似文献
17.
Internal instability is a phenomenon of fine particle redistribution in granular materials under the seepage action and consequent change in the soil’s internal structure and hydraulic and mechanical properties. It is one of the primary causes of failures of sand-gravel foundations and embankment dams. The criteria establishment is considered the key to solving the erosion problems, so the existing internal stability criteria need a review and classification to study the recent development trends in soil seepage and erosion. Therefore, this paper aims at reviewing the internal stability factors of gap-graded soil with a focus on the internal erosion mechanism and internal stability evaluation based on geometric and hydraulic criteria. Firstly, the paper compared the effect of several commonly used geometric criteria for gap-graded soil evaluation, such as particle size, fine content, void ratio, and fractal dimension. Furthermore, it provided a hydraulic criteria overview and analyzed the effects of the hydraulic gradient, hydraulic shear stress, confining pressure, and pore velocity on internal erosion. The geometric–hydraulic coupling methods were introduced, with a detailed elaboration of the erosion resistance index method based on accumulated dissipated energy. The capabilities and limitations of these criteria were discussed throughout the paper. It was found that combined Kezdi’s criterion and Kenney and Lau’s criterion is more reliable to evaluate internal stability of soil. The gap-graded soil with fine particle content higher than 35% is not necessarily internally stable. Finally, the energy-based method (erosion resistance index method) can effectively reproduce the total amount of erosion mass and the final spatial distribution of fine particles and identifies erosion. The review's outcome can be used as a basis to evaluate the internal erosion risk for gap-graded soils. The evaluation methods discussed here can help identify the zones of relatively high erosion potential. 相似文献
18.
This paper describes a modified elasto‐plasticity damage model to capture monotonic and cyclic behavior of the interface between a geotextile and gravelly soil. New damage variable and shear strength criterion are introduced on the basis of test observations. The formulations of the modified model are obtained by extending those of the original interface model. The model parameters with physical meaning are easily determined from a group of cyclic shear tests and a confining compression test. The model predictions are compared with the results of a series of direct shear tests and large‐scale pullout tests. The comparison results demonstrate that the model accurately describes the monotonic and cyclic stress–strain relationship of the interface between a geotextile and gravelly soil while capturing new characteristics: (1) the strength that is nonlinearly dependent on the normal stress; (2) significant shear strain‐softening; (3) the comprehensive volumetric strain response with dependency on the shear direction; and (4) the evolution of behavior associated with the changes in the physical state that includes the geotextile damage. This model is used in a finite element analysis of pullout tests, indicating that the tensile modulus of a geotextile has a significant effect on the response of the geotextile–gravel system. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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