土工织物充填管袋设计计算方法研究

土工织物充填管袋是土工包裹系统的一种,它用编织土工布缝合而成,再用高压泥浆泵充填砂浆,最终形成管状袋体,优点众多,可用于堤坝填筑、抗洪抢险等工程中,应用前景广阔。但目前关于土工管袋形状、高度、张力等参数的计算方法主要是针对高充填压力情况的,而中国实际工程中较多的是充填压力较低即袋体扁平的情况,因此针对目前研究的不足,提出现有无量纲计算方法的适用条件,并对其进行改进,提出低充填压力下的袋体特性计算方法并进行验证,计算结果被制成图表,方便实际应用时查找参数。     

大型疏浚土充填袋筑堤技术研究

为缓解砂石资源紧缺、保护生态环境、降低工程造价和高效利用航道疏浚土,以大型疏浚土充填袋筑堤技术应用于连云港港徐圩港区围堤建设为工程实例,通过稳定性分析计算、离心模型试验开展了大型疏浚土充填袋筑堤技术的理论可行性研究,并结合原型试验提出了新型配套施工工艺,形成了相关成套技术。研究表明:袋体土工织物加筋作用良好,堤体及地基稳定性能够满足安全设计;控制疏浚土充填料初始含水率、采用泥浆泵与浓浆泵串联接力的施工工艺,能够提升大型疏浚土充填袋筑堤施工效率,满足正常围堤建设强度需要;低含水率疏浚土充填料排水较快、袋体实际有效厚度较为理想、堤体地基较为稳定,大型疏浚土充填袋筑堤具有其技术可行性。     

泥浆不均匀时土工织物充填袋特性

与砂土不同,粉土的尺寸比较小,在充填时将很快形成重度不均匀的泥浆。针对泥浆重度不均匀条件下土工织物充填袋形状和力学特性,建立了泥浆重度成线性增加情况下的土工充填袋变形方程,并通过数值方法进行求解。计算结果表明,考虑由于粉土沉淀而导致的重度不均匀时,土工织物充填袋形状更加扁平,所受的拉力增大。因此考虑粉土泥浆沉淀的不均匀性是必要的。     

模袋筑坝沉降分析

土工模袋筑坝的沉降对工程的稳定性有重要影响。为得到土工模袋在工程实践中的沉降量与时间的对应关系,运用沉降量与太沙基一维固结理论及固结度之间的联系,建立沉降量与时间的方程。在已经建立的模袋袋体方程的基础上,根据单个模袋不同高度的充填物所受压力的不同,得到压力与高度的关系曲线,可得随着土颗粒所处的深度的增加其所受的压应力越大,但自身所受的压应力与外压应力相比可忽略不计,通过对压力的积分,再运用太沙基一维固结原理,以此来分析土工模袋自身沉降量与时间的联系。根据建立的方程,分析了多层模袋总沉降与时间的关系,对模袋在筑坝等工程中处于不同时间内的沉降提供了理论指导。     

充填土袋堤变形与稳定离心模型试验研究

利用疏浚土及吹填泥作为充填料的土工织物充填袋筑堤技术得到极大关注。本文针对连云港疏浚土,采用土工离心模型试验技术,研究充填土袋堤体与地基的变形和整体稳定性。试验结果表明:充填土袋堤沉降主要发生在施工期,竣工后沉降变化很小,在堤体范围内沉降呈堤中心大、两边小的锅形分布。充填土黏粒含量对堤身的压缩变形影响较大,充填黏性土与充填砂性土相比,竣工期堤身压缩变形约高11%,竣工一个月后堤身压缩变形约高13%。堤体与地基失稳破坏为圆弧滑动破坏型式,充填黏性土堤稳定安全系数为1.19,充填砂性土堤的稳定安全系数为1.41,表明充填黏粒含量高达32.5%的黏性土筑堤能满足整体稳定要求。     

土工袋柔性挡墙位移模式及土压力研究

用土工袋构筑而成的挡土墙具有一定的柔性, 在墙后土压力作用下,墙体能够发生一定的变形, 墙后土压力分布及大小与刚性挡土墙大不相同。设计并进行了土工袋柔性挡土墙模型试验,通过试验观测了墙体的位移模式和墙后填土的破坏模式,研究了土压力沿墙体高度方向及墙体水平方向的分布;运用水平微分单元法推导了主动平衡状态下土工袋柔性挡土墙土压力的计算公式,土压力理论计算值与模型试验实测值基本吻合;进行了模型试验用土工袋层间摩擦试验,建立了土压力与土工袋层间摩擦力的平衡关系式,分析了土压力沿土工袋墙体水平方向的传递规律。     

固化土充填袋筑堤稳定性的离心模型试验研究

固化土充填袋筑堤技术既节约了日益紧缺的砂石资源,又解决了矿渣和疏浚弃土的处置难题,具有广阔的应用前景。依托天津港某围堤工程,通过开展离心模型试验,研究以钢渣与疏浚弃土为主要原料的固化土充填袋围堤的整体稳定性和变形情况,并分析地基中土压力和孔隙水压力变化规律,试验结果表明：固化土充填袋围堤和地基的沉降主要发生在填筑期,并且沉降速率较大;堤身范围内,沉降呈中间大两边小的锅型分布;从堤脚泥面的沉降曲线和孔隙水压力的消散上看,正常情况下,固化土充填袋围堤和地基能保持稳定状态;固化土充填袋围堤和地基的失稳破坏现为圆弧滑动破坏,变形以沉降为主,水平位移较小,土工织物充填袋对堤体水平变形有很强的约束作用,通过离心模型试验得出的稳定安全系数为1.59。     

土工织物加筋土的土压力减轻作用试验研究

通过在研制改进的固结试验仪上 ,进行一系列考虑土工织物埋置在土中不同位置时加筋土的单轴固结试验及三轴K0 固结试验和不排水剪切试验 ,从静止土压力系数的变化 ,探讨了土中埋置有土工织物的加筋土层的土压力减轻作用及剪切强度的增加作用。得出了土工织物的数量、放置形式和超固结比的不同对土压力变化的影响规律 ,为加筋土边坡稳定分析提供了有意义的参考依据     

环保疏浚联合土工管袋用于湖库底泥的脱水减容

介绍了汉沽污水库现场试验工程采用环保疏浚联合土工管袋的方式,对底泥进行清淤和脱水减容的工程实例,主要内容包括环保疏浚设计、脱水减容场地准备、土工管袋选型、土工管袋充填、絮凝剂投加等.通过对本工程的设计和全过程跟踪实践,摸索出环保疏浚联合土工管袋用于湖库底泥脱水减容的设计参数和操作流程,为今后规模化应用奠定了基础.     

土工织物与砂土界面特性数值模拟研究

文章采用有限元法模拟土工织物加筋土的剪切试验,研究不同上覆土压力、土体强度、加筋体长度、加筋体间距和接触面对直剪试验剪切力-位移即筋土界面本构关系的影响。计算结果表明,土工织物与砂土的界面特性受多种因素的影响。在一定程度上增大上覆土压,提高土体密实度和强度,加大土工织物长度,加密土工织物间距和选择粗糙的土工织物均能提高加筋效果。     

Tension force analysis of geotextile tubes by half cross-section test

A simplified equation, which allows for the calculation of the tension force using the actual tube height and pumping pressure with the flexibility to use a coefficient of lateral pressure (K), is proposed and validated theoretically by comparing the proposed method with two well-known methods in the literature, and experimentally, by conducting several half cross-section tests. The half cross-section test proposed in this study is unique and configured in such a way that the top and bottom of the geotextile tube is supported by load cells to be able to quantitatively measure the maximum tension force, as well as the stress and strain of the geotextile tube. With the use of the simplified equation, the actual field conditions can be exceptionally represented, making it more advantageous over the previous methods.     

珠江三角洲一高速公路软基处理实例分析

针对珠江三角洲一高速公路穿越厚度不均匀的深厚软基,开始采用砂桩结合砂垫层、土工格栅处治,由于填土速度过快及砂桩本身的特点,路基填土出现开裂;后采用卸除填土,并利用预应力混凝土管桩结合钢塑格栅进行处治。通过对整个过程的沉降、侧向位移、孔隙水压力等现场观测数据进行分析,得出在厚度不均匀的深厚软基路段不宜采用无抗剪强度的砂桩处理,宜采用具有一定抗剪强度的处治措施,且加载过程应该采用“薄层轮加法”填筑,确保地基的稳定性。     

孔隙水运移特性及对尾矿细观结构作用机制试验研究

 利用自行研制的尾矿细微观力学与形变观测试验装置,研究尾矿充水过程、荷载作用和排水过程中孔隙水的运移特征及其对尾矿细观结构作用机制。结果显示：尾矿水位线实际达到高度大于计算获得的水位线高度;受荷载作用,充水条件下各层尾矿颗粒沉降位移显著大于未充水条件下相同位置颗粒的沉降位移;充水条件下尾矿颗粒沉降位移随荷载的增加可分为线性增长阶段、显著增长阶段和稳定阶段,显著增长阶段出现在200～400 kPa荷载下;受荷载与孔隙水的作用,尾矿细观结构会形成曲折复杂供水运移的通道,该通道的形成过程发生在尾矿颗粒沉降位移的显著增长阶段;孔隙水夹带尾矿小颗粒运移,对尾矿颗粒分布有一定的影响;尾矿颗粒沉降位移与细观结构受排水影响较小,其变化主要在排水初期。最后,提出水的毛细管作用下尾矿坝实际浸润线的概念与计算方法,研究孔隙水与荷载综合作用下尾矿细观结构变形破坏机制,为深入探索水引起的尾矿坝灾变机制及稳定性评价等具有重要的实际意义。     

考虑σ2作用的加筋土挡墙筋材设计计算

通常加筋土挡墙筋材拉力和锚固区长度的设计计算是基于莫尔-库仑准则得到的，没有考虑中主应力σ2的影响，而双剪强度理论克服了莫尔-库仑准则的不足，并利用双剪强度理论的φ1，Ct参数替代莫尔-库仑抗剪强度指标。基于双剪强度理论（m=1）计算分析了挡墙筋材拉力大小及其锚固区长度，并将该结果与基于莫尔-库仑准则计算的结果进行了对比，结果表明墙高较小时两者结果基本一致，而墙高较大时，双剪强度理论计算结果大于莫尔-库仑准则计算的结果。     

The efficacy and use of small centrifuge for evaluating geotextile tube dewatering performance

Geotextile tube dewatering technology has been widely used over the past two decades for dewatering high water content slurries. The dewatering process in geotextile tubes aims to decrease the volume of the dewatered slurry, which helps in the transportation, disposal, and reuse of the dewatered material. Several researchers have emphasized the effect of the retained sediment (filter cake) properties, in particular final solids content and volume (height) change, on the feasibility of geotextile tube dewatering projects. Retained sediment properties are often evaluated using small scale tests such as rapid dewatering test, falling head test, pressure filtration test (PFT), and field scale tests such as hanging bag test (HBT) and geotextile tube demonstrations test (GDT). In this study, centrifuge test is introduced as an alternative for the widely used pressure filtration and falling head tests to evaluate retained sediments properties. Centrifuge test provides a mechanism for understanding the response of slurries to externally applied pressure in geotextile tube environment. Centrifuge test was used to evaluate maximal solids content of the retained sediments and change in slurry volume of four soils that represent typical dredged soils. Tully sand, Tully fines, Elliott silt loam, and kaolin slurries were used at varying solids concentrations. Slurries were subjected to external stresses between 0.1 and 40 kPa by applying centrifugal speeds between 300 rotation per minute (rpm) and 1800 rpm. Both centrifuge test and PFT were conducted with unconditioned and cationic polyacrylamide conditioned slurries. Centrifuge tests results were compared with PFT results with respect to retained sediments final solids content and volume change. Tests results indicated that the maximal solids concentration of the retained sediments in saturated conditions is unique for each soil and is independent of the initial slurry solids concentration. Tests results also indicated that there is linear relationship between the initial concentration of the slurry and the final volume change at any externally applied stress. Finally, a relationship between the total pumped slurry volume and the final height of the dewatered sediments in a geotextile tube is presented.     

An optimal lightweight foamed mortar mix suitable for tunnel drainage carried out using the composite lining method

In this paper, an optimal lightweight foamed mortar mix suitable is proposed for facilitating tunnel drainage carried out using the composite lining method. A physical performance evaluation and pore structure analysis is provided in order to assess the performance of different lightweight foamed mortar mix proportions with various void fractions and foam solution concentrations. Furthermore, on the basis of an in-plane permeability test that simulated the permeation of fines of soil leaking with underground water, the formation and distribution of open-cell foams by measuring the outflow characteristics and outflow volume for each mix of the nonwoven geotextile and lightweight foamed mortar, which are the existing tunnel drainage materials was examined. Consequently, a mix employing a foaming agent with a dilution rate of 2% (#1) showed a better drain performance than all the other mixes, because it had the most appropriately formed and distributed open-cell foams, the key component for tunnel drainage. In other words, the mix of dilution rate of 2% was thought to have achieved stable closed-cell foams because of the decline in the surface tension of the foams, as well as the optimal formation and distribution of open-cell foams that possess excellent permeability because of the cohesiveness between the foams. Moreover, the thickness (drainage space) of it was approximately 17 times that of the nonwoven geotextile, and because the closed-cell and open-cell foams were connected like a spider web, it could be expected to reduce the blocking of drainage caused by the fines of soil.     

Filtration performance of geotextile encasement to minimize the clogging of stone column during soil liquefaction

Stone columns, which are frequently employed to stabilize the liquefiable soil, are susceptible to accumulation of soil particles. The progressive accumulation of the soil particles causes clogging of the stone column which decreases its drainage capacity. The stone column can be encased with geotextile to sustain its long term drainage function. The encasement prevents the movement of the soil particles into the stone pores. In the present paper, a mathematical model is presented to assess the filtration performance of the geotextile encasement to prevent the clogging. The filtration capacity of the geotextile is related to its maximum pore size, porosity and soil characteristics. It is observed that the encased stone column dissipates the excess pore pressure at a faster rate compared to the stone column without encasement. The peak maximum excess pore water pressure (U_max) is not significantly affected due to selection of the opening size of the geotextiles for single earthquake. However, the opening size can significantly affect the peak U_max value for multiple earthquakes. Depending on the capture coefficient of the stone column, the clogging can be fully prevented for higher hydraulic gradient if geotextile with maximum opening size in between D₁₀ to D₅ is used as encasement.     

深圳湾新吹填超软土固结系数的试验研究

 采用全自动气压固结仪对深圳湾吹填超软土进行大量的固结试验,通过对试验结果的统计分析及与原状淤泥固结系数的对比研究,得出如下结论：(1) 实际工程中,可近似采用压力范围＜100 kPa内统计样本均值线上、压力范围＞100 kPa内对数函数带形宽度内的固结系数,对此区域吹填淤泥的变形及固结速率进行近似估算;(2) 同区域内吹填淤泥固结系数小于原状淤泥的固结系数,随着固结压力的增加,两者间差异性越来越小,说明吹填淤泥经过超载预压处理后,可以达到与原状淤泥相同的排水固结速率。     

Drainage performance of geotextiles

It should be noted that the drainage conditions and mechanisms are somewhat different when geotextiles are used as back fill material behind retaining walls. One of the major differences is that the soil installed by the geotextile may not necessaroly be saturated. Generally, the drainage performance of geotextiles can be evaluated by examining combined behavior of geotextiles, soil particles and water. However, in addition to the above materials, in investigating the drainage performance of geotextiles as back fill material behind retaining walls, the effect of air should be taken into account. Therefore, this study has concentrated on investigating the effect of drainage performance of an initially dry geotextile. A further long-term test was carried out primarily to examine the mechanism and development of self-induced filters, which is believed to determine the drainage performance of the geotextile.     

复合加筋格宾挡土墙施工技术

云南绥江县一中场平工程挡土墙采用新型加筋格宾挡土墙,通过挡土墙设计、坡面清除及基底施工、格宾材料及格宾网箱编织、格宾网箱填石、结构填土及土工织物施工,经检查验收和总体外观鉴定,该挡土墙墙面平顺美观、缝隙均匀、线形顺适,防水排水工程齐全,取弃土位置合理。