A statistical reappraisal of the relationship between liquid limit and specific surface area, cation exchange capacity and activity of clays

More than 500 datasets from the literature have been used to evaluate the relationships of specific surface area (SSA),cation exchange capacity (CEC) and activity versus the liquid limit (LL).The correlations gave R^2 values ranging between 0.71 and 0.92.Independent data were also used to validate the correlations.Estimated SSA values slightly overestimate the measured SSA up to 100 m^2/g.Regarding the estimated CEC values,they overestimated the measured CEC values up to 20 meq/(100 g).A probabilistic approach was performed for the correlations of SSA,CEC and activity versus LL.The analysis shows that the relations of SSA,CEC and activity with LL are robust.Using the LL values,it is possible to assess other basic engineering properties of clays.

Test study of high liquid limit clay modified by quick lime used as sub-grade material

Through laboratory test, the relationships among change of compactibility, liquid/plastic limit, free swell, swell ratio without load, california bearing ratio (CBR) and soakage (after being soaked in water), and mix-ratio of quick lime and time were studied. The results show that optimum water content, plastic limit and CBR of high liquid limit clay improved by quick lime increase with the increase of mix-ratio of quick lime, while the maximum dry density, liquid limit, plasticity index, soakage (after being immersed in water), free swell, and swell ratio without load decrease with the increase of mix-ratio of quick lime. Plastic limit of high liquid clay improved by quick lime gradually increases with time, while the liquid limit, plasticity index, free swell and swell ratio without load gradually decrease with time. When the mix-ratio of quick lime exceeds 2%, after 14 d, swell ratio without load of the improved clay is zero, its free swell is about 30% of that of untreated soil, and its plasticity index is less than 26 for sub-grade material, satisfying the requirement by 'Specifications for Design of Highway Subgrade'.

崩岗土壤液塑限的离子特异性效应

为探究崩岗土壤液塑限的离子特异性效应,选取福建省长汀县河田镇一处稳定型崩岗的3个土层土壤(红土层、砂土层和碎屑层)为研究对象,用液塑限联合测定仪对不同离子(Li^(+)、Na^(+)和K^(+))盐溶液交换处理后的土壤液塑限进行分析。结果表明,红土层的土壤塑限、液限和塑性指数均显著高于砂土层和碎屑层(P<0.05)。土壤塑限和液限均与土壤黏粒含量、有机质含量、阳离子交换量以及高岭石含量呈正相关关系,其中,土壤塑限与黏粒含量和阳离子交换量呈显著正相关关系(P<0.05)。K^(+)交换处理后,红土层土壤塑限、液限和塑性指数比Li^(+)交换处理分别高5.80%、9.53%和12.99%,比Na^(+)交换处理分别高3.50%、9.77%和15.86%;K^(+)交换处理后,砂土层土壤塑限、液限和塑性指数比Li^(+)交换处理分别高7.22%、6.69%和6.83%,比Na^(+)交换处理分别高4.33%、5.27%和7.32%;而不同离子对碎屑层土壤液塑限的影响不显著。不同离子对同一土层土壤液塑限的影响不同,K^(+)交换处理后红土层、砂土层的土壤液塑限总体高于Li^(+)和Na^(+)交换处理,即较Li^(+)和Na^(+)而言,K^(+)可提高崩岗土壤液塑限。

富里酸对红黏土液塑限的影响及其微观机制

通过在红黏土中掺入不同含量的富里酸粉末和蒸馏水制样,并设计不同的浸泡时间,探讨了富里酸对红黏土液塑限的影响规律。试验结果表明,富里酸呈弱酸性,能够溶解土体矿物成分;浸泡时间一定后,土体液限随富里酸粉末与红黏土质量比的增加而减小,塑限先减小后增大;富里酸粉末与红黏土质量比一定时,土体液限随浸泡时间的增加先减小后增大,塑限先增大后减小。

硅酸钾溶液对黏性土体微观结构的影响研究

为更好满足工程中的要求,土的改良成为一道重要工序,改良后的土体其抗剪强度及液塑限都会产生变化。在黏性土中加入硅酸钾溶液,进行改良,研究其抗剪强度以及液塑限的变化。对改良后的试样进行了快剪直剪试验和土体液塑限试验,探讨了硅酸钾溶液改良土的抗剪强度及其液限塑限的变化规律。进行电子扫描试验得到不同土体试样的微观结构图,并利用Image-Pro Plus图像处理软件计算含不同硅酸钾溶液浓度的改良土样的微观参数,解释其内在机理。

California Bearing Ratio for Cohesive Soils from Quasi Static Cone Tests

The California bearing ratio (CBR) test is the most widely spread method of determining the bearing strength of the pavement material and is fundamental to pavement design practice in most countries. This test is expensive, laborious and time consuming, and to overcome this, Quasi static cone penetrometer machine was fabricated and used to measure the consistency limits (liquid limit-LL, Plastic limit-PL and Plasticity index-PI), which were used to develop an empirical equation to determine CBR. Soil samples were collected and unsoaked CBR, PL, LL and PI were determined according to BS 1377 part 9 and BS 1377-2;1990. Quasi static penetration forces at 20 mm depth of penetration were also determined at consistency limits. It was found that the force of 1020 gf and 60 gf was achieved at a depth of 20 mm at PI and LL respectively. The correlation and regression analysis between consistency limits, and the experimental CBR obtained showed coefficient of determination, R2 = 0.907 between CBR and all the parameters using multiple linear regression analysis (MLRA). The regression equation developed was used together with the relationship developed between the Quasi static Penetration force at consistency limits and the tested consistency limits to come up with the General Empirical Equation. Verification of the formula showed that the correlation can be used accurately to determine the un soaked CBR.

Identification of Empirical Models for the Prediction of the Plasticity Index:Case of the KhôDepression in South Benin

The plasticity index is an essential design parameter used as a standard input in fine-grained soil investigation programs.It is used to estimate the plasticity and physical properties of soils,and indirectly their strength properties.This index is determined from the Atterberg limit tests,starting from the limits of liquidity and plasticity.However,the realization of the test considered as basic and simple,is not so much.The effects of the operator,the calibration of the apparatus and the environmental aspects during the tests affect the reliability and accuracy of the results.In this paper,the objective is to overcome these difficulties by evaluating the plasticity index of clay and loam soils by considering only the values of the liquid limit.Soil samples were collected from 0 to 5 m depth in the localities of the Khôdepression in Benin.On these samples,Atterberg limit tests were performed in the laboratory.Using MATLAB’s Curve Fitting Toolbox,linear,exponential and power prediction models were analyzed.The results showed that there is indeed a good correlation between the plasticity index and the liquid limit of the soils.For the linear model,it was observed R2 equal to 0.9891.For the exponential model,R2 is 0.98871 and for the power model 0.9802.A study of the residual plot validated the models found,as well as comparisons with well-known literature sources.Through the equations obtained,it is now possible to study the plasticity of soils in the Khôdepression only from the liquid limit,without determining the plasticity limit.

7种重塑黏土的一维压缩-卸荷行为

重塑黏土的一维压缩-卸荷行为是黏土最基本的力学特征。为此,开展系统的7种重塑黏土一维压缩-卸荷试验与相应物理化学性质指标及矿物成分测试,在此基础上,评价黏土压缩-卸荷行为经典预测公式的适用性。结论如下:(1)4个经典压缩指数公式预测效果均较好,其中Nagaraj公式最优。(2)7种重塑黏土孔隙比指数-有效一维固结压力关系与Burland固有压缩线经验公式几乎重合。(3)Nagaraj、Burland一维压缩曲线方程预测效果均较好,其中Burland方程更优。(4)Nagaraj、Kulhawy回弹指数公式预测效果均较好,其中Kulhawy公式更优。(5)压缩指数、回弹指数与比表面积、阳离子交换量均有很强的相关性,且与比表面积的相关性强于与阳离子交换量的相关性。(6)压缩指数与回弹指数比值最低为3.0,最高为10.2,超出了5~10的范围,且随塑性增大而降低。

木质素磺酸钙改良黄土液塑限试验研究

木质素磺酸钙是一种复杂的高分子聚合物,可有效改善土体物理力学特性,选取兰州地区黄土,对木质素磺酸钙不同掺量和养护龄期条件下改良黄土液塑限的变化规律进行试验研究。试验结果表明:随着木质素磺酸钙掺量的增大,改良黄土的液限、塑限均呈现出减小的趋势。塑性指数随木质素磺酸钙掺量增加呈略微降低趋势,且随着掺量增大,改良黄土的塑性指数趋于7~8之间。

不同改良剂对红黏土液塑限的影响研究

在实际道路施工中遇到红黏土,一般采用改良剂对其进行改良。红黏土改良之后,需要重新测定物性指标,液塑限是其中的一个重要指标。以三明将乐动车站右侧取土场的红黏土作为试验土样,以石灰、粉煤灰、玄武岩纤维和氯化镁作为改良剂,通过界限含水率试验,研究不同改良剂在不同掺量下对红黏土液塑限的影响。研究表明:液限随着改良剂掺量的增加而减少,使用氯化镁改良的红黏土液限降幅最大;塑限随着氯化镁掺量和粉煤灰掺量的增加而减少,随着石灰掺量和玄武岩纤维掺量的增加而增加;塑性指数随着氯化镁掺量、石灰掺量和玄武岩纤维掺量的增加而减少,随着粉煤灰掺量的增加而增加。

Mineralogical and Geochemical Assessment of Clay Properties of Edda, Afikpo Sub Basin Nigeria for Possible Use in the Ceramics Industry

Clay samples from selected part of Edda were analyzed to identify the clay mineral types present,their chemical and physical properties with a view to appraising their industrial suitability as ceramic materials.The mineralogical and geochemical analyses were done using the principles of X-Ray diffraction and X-ray fluorescence respectively.A total of seven clay samples were used for the study,other tests such as plasticity,bulk density,shrinkage,loss on ignition(LOI)and water absorption capacity was carried out to determine the amount of water absorbed under specified conditions.The basic industrial properties assessment showed that more than 70%of the clays are fine-grained.The clays exhibited low to moderate plasticity,moderate shrinkage and bulk density,low to moderate values of both loss on ignition and water absorption capacity.The clays are buff to yellowish in colour.The results of x-ray fluorescence revealed that the mean concentration of major oxide in the clays is shown as follows:SiO_(2)(62.78%),Al_(2)O_(3)(20.25%),total Fe(6.09%),CaO(0.56%),MgO(3.21%),Na_(2)O(0.47%),K_(2)O,(1.44%)and TiO_(2)(0.52%).The samples have high silica content,low alumina and low oxide content.The results of x-ray diffraction revealed that kaolinite is the dominant clay mineral with illite and montmorillonite occurring in subordinate amounts,while quartz and feldspar are the non-clay components present.The characteristics of the clays for each parameter were compared with industrial standards.These properties are appropriate for the Afikpo clays to be useful in the manufacturing of ceramics.However,since the silica content of the clays is high further beneficiation is recommended.

Comparison of properties of traditional and accelerated carbonated solidified/stabilized contaminated soils

The investigation of the long-term performance of solidified/stabilized （S/S） contaminated soils was carried out in a trial site in southeast UK. The soils were exposed to the maximum natural weathering for four years and sampled at various depths in a controlled manner. The chemical properties （e.g., degree of carbonation （DOC）, pH, electrical conductivity （EC）） and physical properties （e.g., moisture content （MC）, liquid limit CLL）, plastic limit （PL）, plasticity index （PI）） of the samples untreated and treated with the traditional and accelerated carbonated S/S processes were analyzed. Their variations on the depths of the soils were also studied. The result showed that the broad geotechnical properties of the soils, manifested in their PIs, were related to the concentration of the water soluble ions and in particular the free calcium ions. The samples treated with the accelerated carbonation technology （ACT）, and the untreated samples contained limited number of free calcium ions in solutions and consequently interacted with waters in a similar way. Compared with the traditional cement-based S/S technology, e.g., treatment with ordinary portland cement （OPC） or EnvirOceM, ACT caused the increase of the PI of the treated soil and made it more stable during long-term weathering. The PI values for the four soils ascended according to the order： the EnvirOceM soil, the OPC soil, the ACT soil, and the untreated soil while their pH and EC values descended according to the same order.

酸污染红土物理性质的变化特征

考虑酸浓度和养护时间的影响,通过室内试验对比研究了酸污染红土的颗粒组成、比重和界限含水率等物理特性。研究结果表明:不洗盐、加分散剂,酸浓度较低时粉粒含量减小,酸浓度较高时粉粒含量增大;随养护时间延长,浓度较低时粉粒含量减小,浓度较高时粉粒含量先增后减;洗盐后粉粒含量减小,不加分散剂粉粒含量增大。酸污染红土的比重、液塑限与塑性指数随酸浓度的增大和养护时间的延长总体都呈减小的趋势。酸污染红土物理性质的变化可以从酸污染红土所存在的腐蚀、成盐和溶解三个阶段来解释。

浙江沿海地区软土工程特性

基于 66项软土地基工程的试验成果 ,系统分析研究了浙江沿海地区软土物理力学指标、地域分布规律及指标间的相互关系 ,较好地揭示了该地区的软土工程特性 ,对今后的工程建设具备指导作用 .

崩岗红土层土壤液塑限特性及影响因素研究

土壤液塑限可以反映土壤的入渗、抗冲、抗蚀和抗剪等情况,对崩岗的水土流失研究有重要的意义。通过对崩岗红土层土壤的液塑限研究以及颗粒分析和有机质测定,分析土壤有机质含量和土壤颗粒分布对土壤液塑限的影响。结果表明:崩岗红土层土壤为高液限黏土,土壤状态为坚硬;土壤液塑限值与粗砂粒、细砂粒和粉粒含量相关性不明显,与极细砂粒和黏粒含量呈二项式关系,其中极细砂粒含量与土壤液塑限呈负相关;黏粒含量与土壤液塑限均呈显著正相关关系,且模拟的方程可以较准确地描述土壤液塑限和各因素的相关关系。研究结果有利于丰富崩岗侵蚀机理的研究。

重金属锌污染淤泥质粉质粘土物理特性试验研究

重金属污染在我国已受到普遍关注,而对重金属污染土的物理特性的研究还处于起步阶段。采用南京地区特有的粉质粘土、长江漫滩相淤泥质粉质粘土,进行相关的重金属锌污染后的物理特性研究。通过室内添加硝酸锌溶液配制3种不同浓度的重金属锌污染土,并进行土壤污染前后粒度成分、液塑限、活动度、土粒比重以及pH值等试验的测试分析,研究比较了粉质粘土污染前后随着重金属锌的浓度不同其相关物理性质的变化规律。试验表明,随着Zn浓度的增加,土粒比重,液塑限,粉粒含量和pH值减小,而粘粒含量和塑性指数呈增大趋势。其土体的活动度也随着Zn浓度的增加在不断的降低,并且降低趋势逐渐减缓。

基床翻浆冒泥土的物理力学性质

随着列车提速和轴重大幅增加,基床出现翻浆冒泥病害的几率加大.为了进一步研究翻浆冒泥发生机理和探究其发生条件,系统研究了60多组翻浆冒泥实例,分析了翻浆冒泥土的颗粒组成、可塑性指标、渗透性及矿物成分等物理力学性质.研究结果表明:翻浆冒泥土中,绝大部分黏粒含量大于20%、粉粒含量大于20%,黏粒含量大于30%和粉粒含量大于40%的土所占数量最多;翻浆冒泥土中粉粒的含量一般要高于黏粒含量;翻浆冒泥土(主要包括砂黏土、粉质黏土、黏土和部分低液限粉质黏土)液限大于23%,塑性指数大于6.5;翻浆冒泥土渗透系数小于1.0×10^(-5)m/s;翻浆冒泥土的渗透系数与细颗粒含量之间存在较好的负指数关系.

落锥法确定粉土液限和塑限的试验研究

针对部分细粒土进行了室内落锥法确定液限和塑限的试验研究,试验结果表明:对于一些细粒土在双对数坐标上圆锥下沉深度与含水率之间的关系并非线性关系,无法依据线性关系确定液、塑限;采用规程建议的3个含水率范围有时根本无法获得有效试验数据,采用规程建议的3个含水率范围确定得到粉土的液、塑限试验结果的可靠性有待商榷;采用直线段试验数据确定的液、塑限进行分类可能出现相互矛盾甚至错误的结果。进一步试验结果表明:对于黏粒含量高于13%的粉土,由于其抗剪强度以凝聚分量为主,落锥法适用,所测塑性指数能够反映其可塑性;对于部分黏粒含量低于13%的粉土及外观接近粉土的粉砂,由于其抗剪强度以颗粒间摩擦分量为主,落锥法不再适用,所测塑性指数不能反映其可塑性。

pH值对桂林红黏土界限含水率的影响及其机理分析

液塑限是影响黏土抗渗透、抗冲切、抗冲刷、抗侵蚀、抗剪切的重要因素之一。为研究红黏土的界限含水率的影响因素及其作用机理,对不同pH值溶液作用下红黏土的液塑限进行测试。试验结果表明,酸性溶液中,随着pH值的减小,红黏土塑限降低,液限与塑性指数则先降低后增大;碱性溶液中,随pH值的增大,塑限、液限均表现为先减小后增大,塑性指数表现为折线变化。经分析表明,传统的扩散层厚度影响因素及双电层理论均不适用于分析不同pH值条件下的桂林红黏土稠度界限。根据相同土的液塑限对应电势一定的原则,在双电层模型的基础上,提出双电层结构模型定性分析红黏土稠度界限的方法。基于传统双电层理论,考虑多种成分溶液作用下,推导了适合桂林红黏土在酸碱液作用下的扩散层厚度计算公式,弥补常规扩散层厚度计算公式仅适用于对称电解质溶液作用的恒定电荷黏土的不足。

洗衣粉污染土压缩特性及电阻率的试验研究

采用人工拌和方法制备4种不同洗衣粉含量的污染粉土，通过常规土工试验、压缩试验和电阻率测试，研究洗衣粉含量对土体稠度指标和压缩性的影响以及电阻率变化特性。试验结果表明：洗衣粉污染土的液、塑限随洗衣粉含量的增加而增大；当洗衣粉质量分数〈9g／kg时，污染土的液、塑限值小于无污染土的液、塑限值，洗衣粉污染土的塑性指数均大于无污染土，塑性指数随洗衣粉含量增加而增大；当含量达到9g／kg时，塑性指数达到最大值；之后随洗衣粉含量进一步提高，塑性指数减小。压缩试验表明，除洗衣粉含量为1．5g／kg的污染土外，当压力区间在600kPa以内时，污染土的压缩性均高于无污染土；当压力小于400kPa时，随洗衣粉含量提高，污染土的压缩性先增大后减小；随着压力增大，污染土与无污染土的压缩性均表现出减小的趋势，当压力为600-800kPa时，污染土的压缩性与无污染土的压缩性趋于相同，后者略大于前者。污染土的电阻率与洗衣粉含量存在负指数相关，基于阿尔奇电阻率模型，建立了推广的洗衣粉污染土的电阻率模型。