含盐量对石灰固化滨海盐渍土力学强度影响试验研究

随含盐量的增加,滨海盐渍土中的盐分结晶形成了许多晶体颗粒,改变了土的颗粒级配和微结构形式,使土的力学强度发生变化。无侧限抗压试验和三轴压缩试验结果表明,随含盐量的增加,石灰固化土的无侧限抗压强度和抗剪强度降低;随养护龄期的增加,石灰固化土的无侧限抗压强度和抗剪强度增加;随含盐量的增加,固化土试样浸水和不浸水无侧限抗压强度之间的差值越来越小。工程应用滨海盐渍土时需控制土的含盐量。     

随机分布剑麻纤维加筋土力学性能试验研究

把剑麻纤维剪切为0.5、1.0、1.5cm,并分别按0.2%、0.4%、0.6%的质量百分含量掺入到粘土中,对剑麻纤维加筋土进行无侧限抗压试验和直接剪切试验,并与未掺入剑麻纤维的初始土样的无侧限抗压强度与直接剪试验结果进行对比。试验结果表明,剑麻纤维的掺入可以有效提高粘性土的无侧限抗压强度和抗剪强度;当剑麻纤维的含量和长度达到一定值后,其中1组的无侧限抗压强度值和抗剪强度值要大于另3组对应的无侧限抗压强度值和抗剪强度值。
     

pH值对湿陷性黄土物理力学性能及微观结构的影响

酸碱污染严重影响岩土工程长期稳定性。利用无侧限抗压强度、湿陷性试验、抗剪强度试验,研究不同pH值对黄土物理力学性能的影响,并采用XRD、SEM进一步探究不同pH值对黄土的影响机理。试验结果表明,与对照组相比（pH=7）,pH值降低导致矿物成分衍射峰强度明显下降,且pH=3与pH=5中孔与大孔分别占比93.3%、89.9%,进而使无侧限抗压强度、湿陷性、抗剪强度下降。随pH值增加,在碱性环境中会生成大量胶凝物质,矿物成分衍射峰强度提高,与pH=7相比,p H=9与pH=11微孔与小孔分别增加25.0%、59.96%,使黄土物理力学性能得到提升。酸污染会降低黄土物理力学性能,而碱污染可提高黄土物理力学性能,可为黄土地区酸碱污染防治提供参考依据。     

云母影响水泥软黏土强度的试验研究

软黏土具有压缩性强、承载能力低的特点,实际工程中多用水泥作为固化剂对软黏土进行加固。云母是软黏土中较为常见的一种片状矿物,其含量和颗粒大小会影响水泥加固后的软黏土即水泥软黏土的强度。通过无侧限抗压强度试验和直接剪切试验研究云母含量及目数对水泥软黏土抗压强度及抗剪强度的影响,提出了云母含量、目数与水泥软黏土抗压强度、抗剪强度指标值之间的关系。试验中云母目数设定为10,20,40,80目共4个梯度,云母含量设定为0%、8%、16%、24%、32%共5个梯度。试验结果表明,云母含量的增加以及云母目数的减小会导致水泥软黏土无侧限抗压强度和抗剪强度的降低,且其对无侧限抗压强度的不利影响更为显著。含10目32%云母的水泥软黏土的强度减少量最大,此时无侧限抗压强度为0.33 MPa,是不含云母水泥软黏土的25.5%;黏聚力为76.5 kPa,比不含云母时减少了12.24 kPa;内摩擦角由不含云母时的23.71°降低至21.77°。云母自身的片状形态及其对水泥水解水化作用、离子交换作用的阻碍是造成水泥软黏土强度降低的主要原因。     

电镀场地重金属铬污染土固化率及稳定性研究

为了解决宁波地区电镀场地重金属污染问题,研究利用自配固化剂开展铬污染土的毒性浸出试验、无侧限抗压强度试验、动荷载作用下的长期稳定性试验以及扫描电镜试验。在此基础上分析固化土的力学特性、浸出特性等随养护龄期、固化剂掺量、固化剂配比、铬污染水平的变化规律。结果表明：自配固化剂对铬污染土的固化率均达85%以上,固化率大体上随...     

碱渣改良膨胀土室内试验研究

通过室内试验,探讨利用碱渣作为添加剂对膨胀土改良的可行性和改良效果和碱渣改性土的基本物理力学性质和膨胀性。研究结果表明,随着掺渣率的增加,碱渣改性土的黏性成分的含量降低,粗颗粒含量增加,导致相对密度、液限、塑性指数、自由膨胀率、有荷膨胀量均呈明显减小趋势,这说明碱渣对膨胀土膨胀性的改良有显著效果;碱渣改性土可击实含水率范围较之膨胀土宽,这给碱渣改性土的施工带来很大方便;经过7 d养护后的土样无侧限抗压强度和抗剪强度都显著增加,并在掺渣率为30%时存在一个峰值点。抗剪强度增强主要体现在黏聚力显著增加,而内摩擦角变化不大。     

水泥固化锌污染土电阻率与强度特性研究

以标准砂及普通硅酸盐水泥为试验材料,制作水泥固化锌污染土样,进行了一系列电阻率和无侧限抗压强度试验。研究了交流电频率对水泥固化锌污染土电阻率的影响、不同含量锌离子对水泥缓凝作用的影响、锌离子含量和龄期分别对水泥土电阻率和强度的影响、电阻率与无侧限抗压强度的关系。结果表明：电阻率随电流频率的增加而明显降低,尤其当频率低于50 kHz时为甚;不同含量的锌离子对水泥土的缓凝作用影响明显,随着锌离子含量的增大,水泥土强度的充分发挥所需时间逐渐增长,但在锌离子含量为500 mg/kg时,缓凝作用表现异常;电阻率和强度均随龄期的增加而增长,随锌离子的含量的增加上下波动,电阻率在锌离子含量为50 mg/kg和500 mg/kg时出现极值,强度在锌离子含量为100 mg/kg和500 mg/kg时出现极值;在各个龄期下,电阻率与强度均呈现出很好的线性关系。     

基于最优含水率的聚丙烯纤维增强膨胀土强度研究

将不同长度的聚丙烯纤维按照0.0%、0.1%、0.2%、0.3%和0.4%的重量比分别掺入膨胀土中配制试样,通过大量的室内试验研究了聚丙烯纤维对膨胀土强度的影响规律。试验结果表明:随着纤维的加入,膨胀土的抗剪强度得到了明显的增强,且无侧限抗压强度也随着纤维含量的增加而急剧增加,但当纤维含量超过最优加筋量0.3%时,加筋膨胀土的无侧限抗压强度和抗剪强度反而呈现降低趋势。相同纤维含量的情况下,膨胀土的强度也会随着纤维长度的增加而明显增加,同时聚丙烯纤维还可以增加纤维复合膨胀土的峰值强度,延缓土样的破坏,其研究结果为膨胀土性质的改良提供一种可借鉴的方法。     

武汉地区一级阶地黏性土电阻率试验研究

通过电阻率原位测试和室内土工试验,研究黏性土电阻率特性及电阻率与岩土参数的相互关系。在武汉市轨道交通7号线勘察过程中,沿轨道走向,在长江一级阶地共布置完成电阻率测井22组,并于测井位置采取原状土样进行常规土工试验、无侧限抗压试验、直剪快剪试验及三轴UU试验。通过研究发现:黏性土电阻率随含水量及孔隙比的增加而增加,随无侧限抗压强度增加而减小。根据黏性土三轴UU试验结果,其电阻率随黏聚力、内摩擦角的增加而减小。通过拟合,给出了黏性土电阻率与岩土参数间的经验公式,其相关性显著。     

活性氧化镁−微生物固化黄土试验研究

以活性氧化镁和微生物共同作用固化的黄土试样为研究对象,通过含水率、无侧限抗压强度、X射线衍射（XRD）和扫描电镜（SEM）等试验,研究了活性氧化镁掺量、养护龄期和初始含水率对固化试样含水率、无侧限抗压强度、固化产物和微观结构等的影响。结果表明：固化试样含水率随氧化镁掺量增加和养护龄期增长而降低;无侧限抗压强度随活性氧化镁掺量（5%～20%）增加而增大,随龄期发展总体上不断增大,但当氧化镁掺量为10%和15%时,后期强度稍有降低;当氧化镁掺量为5%和10%时,无侧限抗压强度随初始含水率增加而减小,而当氧化镁掺量为15%和20%时,无侧限抗压强度随初始含水率增加先增大后减小。XRD和SEM结果显示,随着氧化镁掺量增加,水化后未进一步反应的氢氧化镁越多;反应生成的水合碳酸镁具有膨胀性和胶结性,对土颗粒间缝隙进行填充,并将土颗粒胶结在一起。     

黄土的构度指标及其试验确定方法

黄土的结构性是一个重要的物理性质指标,它与土的粒度、密度和湿度一起影响土的力学性质。依据加荷、扰动、浸水释放土结构势的方法,由土的无侧限抗压强度定义了黄土结构性的构度指标。通过多个场地不同黄土的无侧限单轴压缩试验,测试分析了不同含水率原状土、重塑土和饱和原状土的单轴压缩应力-应变曲线及无侧限抗压强度变化规律,由此得出土的构度指标的变化规律。并且,在粒度、密度、湿度相似条件下,比较分析了土的构度指标与其压缩性之间的关系。土的构度指标与粒度、密度和湿度指标一起能够合理描述土的物理力学基本性质。     

陕西延安Q_2原状黄土抗拉强度试验研究

对陕西延安新宝塔山隧道Q2原状黄土进行了不同加载速率的无侧限抗压与贯入抗拉试验,研究了Q2原状黄土抗压与抗拉强度的影响因素。结果表明:加载速率对宝塔山Q2原状黄土抗压和抗拉强度影响较大,抗压强度与抗拉强度随加载速率增大而增大;高径比对抗拉强度也有较大影响,试验时当高径比控制在1.0左右时,高径比对宝塔山Q2原状黄土的抗拉强度影响相对较小,因此采用轴向压裂法测量黄土的抗拉强度时,高径比宜控制在1.0;在试验加载速率范围内,加载速率对宝塔山Q2原状黄土的压拉比影响不大,其压拉比在9.88~13.68范围内变化。     

石灰改性红砂岩残积土工程性质试验研究

为研究石灰改性红砂岩残积土的工程性质并确定最佳掺量,以恩施地区红砂岩残积土为研究对象,制备不同石灰掺量的改良土试样,并进行击实、压缩、无侧限抗压试验。结果表明,随着石灰掺量的增大:改良土最优含水量逐渐增大,最大干密度逐渐减小;改良土压缩系数先减小后增大,压缩模量先增大后减小,对应的最优石灰掺量为7%;改良土无侧限抗压强度先提高后降低,对应的最优石灰掺量为9%。出现上述规律的主要原因是:石灰发生的水化、离子交换、碳酸化、结晶等作用,增强了砂土颗粒之间的黏结,提高了土的整体性,使石灰土压缩、强度特性得到改良。然而,过多的石灰会以自由灰的形式存在于土颗粒空隙之间,导致土体的压缩变形量增大,无侧限抗压强度降低。     

尾矿坝筑坝模袋力学性能试验研究

模袋法是解决上游法细粒尾矿堆坝难的一种新方法。为研究模袋法尾矿坝筑坝模袋的基本力学性能,采用与云南省某尾矿坝施工现场一样的土工布和尾砂,通过斜坡滑移、直剪、无侧限压缩试验,对固结不同时间的小尺寸尾矿坝筑坝模袋进行了摩擦和受压性能的试验研究。斜坡滑移试验表明,若含水率相对较低,则模袋间的摩擦系数较大;直剪试验测得固结8 d的模袋间内摩擦角约为28º,黏聚力约为40 kPa;在无侧限压缩条件下,固结1 d和3 d的模袋在受压过程中,其弹性模量都表现为“大-小-大”的变化形式。由于土工布和尾砂的共同作用,模袋的极限抗压强度远大于单纯尾砂堆积体的极限抗压强度。当压应力达到模袋所能承受的极限荷载时,通常会在模袋底部靠近模袋边缘处发生土工布的撕裂破坏,采用主动土压力理论分析了发生破坏的原因。本试验研究可以为模袋法尾矿坝的实践提供理论指导。     

Utilization of red mud as a stabilization material for the preparation of clay liners

Red mud is a waste material generated by the Bayer Process widely used to produce alumina from bauxite throughout the world. Approximately, 35% to 40% per ton of bauxite treated using the Bayer Process ends up as red mud waste. Because of storing issues, the waste negatively affects the environment. To solve this problem, it is essential to investigate different uses for red mud waste. The potential use of red mud for the preparation of stabilization material is presented in this study. This study examines the effects of red mud on the unconfined compressive strength, hydraulic conductivity, and swelling percentage of compacted clay liners as a hydraulic barrier. The test results show that compacted clay samples containing red mud and cement–red mud additives have a high compressive strength and decreased the hydraulic conductivity and swelling percentage as compared to natural clay samples. Consequently, it is concluded that red mud and cement–red mud materials can be successfully used for the stabilization of clay liners in geotechnical applications.     

Laboratory determination of mechanical and hydraulic properties of chemically grouted sands

The purpose of this paper is to investigate mechanical and hydraulic properties of sands treated with mineral-based grouts through the results of a laboratory test programme consisting of unconfined compression tests (UCS), triaxial bender element tests (BeT) and constant flow permeability tests in triaxial apparatus. An improved apparatus was set up for obtaining high quality, multiple grouted specimens from a single column. Two selected natural sands having different grain sizes were grouted with two mineral-based silica grouts, resulting in different levels of improvement. The behaviour of the sands treated by mineral grouts, in terms of strength, initial stiffness and permeability, was compared with that exhibited by more traditional silicate grouts. The results of this study indicate that sands treated with mineral grouts result in higher strengths, higher initial shear modulus and lower permeability values than the sands treated with the silicate solution. The effect of grout type, effective confining pressure, and sand particle-size on small-strain shear modulus of grouted sand specimens was evaluated. Based on test results, the small strain shear modulus increment from treated to untreated specimens has been correlated with the unconfined compressive strength, obtaining a unique relationship regardless of grout type and grain-size of tested sands.     

膨胀土与红黏土石灰改性对比试验研究

为探讨石灰改性膨胀土与红黏土的强度发展规律,以生石灰与消石灰改性的南阳膨胀土与郴州红黏土为研究对象,进行了无侧限抗压、固结快速直剪和固结压缩试验的对比研究。研究发现：在1 a养生龄期内,石灰改性的南阳膨胀土与郴州红黏土无侧限抗压强度与养生龄期的对数基本呈线性关系;按大于最佳含水率3%制样的强度在养生28 d以后高于按最佳含水率制样;生石灰改性效果比消石灰改性效果好,由于矿物成分不同,石灰改性南阳膨胀土的效果比石灰改性郴州红黏土好     

Deformation Modulus of Fly Ash Modified with Lime and Gypsum

Deformation modulus of fly ash is one of the most important mechanical properties generally used in different design problems and also as an input parameter to sophisticated numerical techniques employed to assess the response of different structures resting on fly ash fill or embankment made of fly ash. Deformation modulus is usually expressed in terms of compressive strength. This paper presents the deformation modulus of fly ash modified with lime alone or in combination with gypsum at different strain levels. The values of deformation modulus obtained from both unconfined compression test and unconsolidated undrained triaxial test results are presented herein. The specimens for unconfined compression test and for undrained triaxial tests were cured up to 90 and 28 days, respectively. The effects of addition of lime (4–10%) and gypsum (0.5 and 1.0%) on the deformation modulus of class F fly ash are highlighted. With addition of lime and gypsum, the class F fly ash achieved the deformation modulus in the range of 190 MPa in UCS test and up to 300 MPa in triaxial test specimens tested under all round pressure of 0.4 MPa. Based on the present test results empirical relationships are developed to estimate deformation modulus of modified fly ash from unconfined compressive strength and relationships between initial tangent modulus and secant modulus at different strain levels are also developed.     

Shear strength characteristics of Irbid clayey soil mixed with iron filling and iron filling–cement mixture

Iron filling and iron filling–cement mixture were used to improve the shear strength characteristics of Irbid clayey soil. For this purpose, five types of Irbid clay soils were obtained and mixed with iron filling and iron filling–cement mixture at different percentages. Two sets of prepared samples were mixed with the admixture. The first set was prepared by mixing the soil samples with iron filling alone at 2.5, 5.0, 7.5, and 10% by dry weight of the soil. The second set was prepared by mixing with iron filling–cement mixture at equal ratio of the same percentages of the first set. An unconfined compression test was performed in this study to measure the shear strength properties of the soils. The test results showed that the increase in the percentages of the iron filling and iron filling–cement mixture up to 10% will result in increasing the maximum dry density of the soil and increase the unconfined compressive strength and the secant of modulus of elasticity of the clayey soil. Also, the addition of iron filling–cement mixture increased the unconfined compressive strength and secant modulus of elasticity of the clayey soil higher than the addition of iron filling alone.     

饱和击实黄土的动力特性研究

通过进行不同固结条件下饱和击实黄土的动三轴试验,研究了饱和击实黄土的动模量、阻尼比、动强度、动孔压及抗液化特性。研究结果表明：饱和击实黄土的动应力-应变关系符合双曲线模型,模型中参数起始动剪切模量和最大动应力与轴向固结应力间均有良好的幂函数关系,且可以对不同固结应力状态归一,固结围压和固结比对阻尼比的影响较小。动剪应力比随固结围压的增大而减小,随固结比的增大而增大。固结围压、固结比以及动应力皆对动孔压比（ ）与振次比关系有显著的影响,而动孔压与破坏时动孔压之比与振次比关系只受固结围压变化的影响,基本上不受固结比和动应力变化的影响,可以用幂函数关系来模拟;在均压固结条件下,当破坏振次小于等于30时,饱和击实黄土不会产生液化,而当破坏振次较大（动应力较小）时可以产生液化;在偏压固结条件下不会产生液化。