不同水泥土力学性能试验研究

对不同龄期和不同水泥掺量的5种水泥土试样进行了无侧限抗压强度试验,得到了5种不同水泥土在不同水泥掺量和不同龄期时的无侧限抗压强度值及不同水泥土力学性能的规律。试验表明,水泥土在一定的水泥掺量范围内其抗压强度增加显著,超过此范围后,抗压强度增加幅度有限。水泥土龄期60d以前,水泥土强度增长较快,龄期60d后水泥土强度虽有所增加,但增长幅度不大。同时,对试验结果进行了回归分析,得到了不同龄期水泥土无侧限抗压强度的推算公式及水泥土无侧限抗压强度与水泥掺量、不同龄期水泥土无侧限抗压强度之比与水泥掺量之比和不同水泥掺量水泥土无侧限抗压强度之比与龄期之比间的推算公式。     

聚丙烯纤维掺量对水泥土强度特性的影响研究

水泥固化土中掺入聚丙烯纤维,可以对土体强度进行一定的改良。本文以聚丙烯纤维掺量为研究变量,掺入0%、0.1%、0.2%、0.4%的9mm长纤维和15%水泥,制备纤维水泥土,通过无侧限抗压强度试验和常规三轴试验,分析了聚丙烯纤维掺量对水泥土强度特性的影响。试验结果表明:纤维水泥土的无侧限抗压强度随纤维含量的增加而增强,纤维含量对纤维水泥土无侧限抗压强度的提高效果很明显。28d龄期掺入0.4%纤维的水泥土,其无侧限抗压强度是不掺纤维水泥土的1.60倍。纤维的掺入能提高水泥土的峰值应力和增大破坏应变,并且随纤维含量的增加,水泥土的粘聚力逐渐增大,而其内摩擦角却变化不大。纤维水泥土在受压过程中,纤维的掺入能够为土体提供一定的拉应力,从而能在一定程度上阻止试样裂缝的开展。     

水泥土无侧限抗压强度的试验研究

分析了土的塑性、水泥和外加剂掺量对水泥无侧限抗压强度的影响。试验结果表明,水泥土无侧限抗压强度随土的塑限增大而先减小后增大,随着水泥掺量的增加,水泥土无侧限抗压强度有明显增长,掺了减水剂的水泥土的7 d强度有所增加,但以后强度几乎没有增长。     

聚乙烯醇改性混杂纤维水泥土强度特性分析

为研究聚乙烯醇(PVA)对纤维水泥土强度的影响规律和作用机制,将占水泥质量2%,5%,10%的PVA分别与聚丙烯纤维水泥土、玻璃纤维水泥土及二者混杂纤维水泥土混合均匀,共配制16组试样进行无侧限抗压强度试验,并采用扫描电镜(SEM)观察PVA掺入后水泥土的形态特征。结果表明,掺入2种纤维均可显著提高水泥土无侧限抗压强度。PVA掺量对纤维水泥土的强度有重要影响,随PVA掺量的增加,纤维水泥土无侧限抗压强度先增加后减小。在PVA掺量为5%时纤维的加筋作用达到最优,此时无侧限抗压强度最大。水泥及PVA的水化产物使纤维表面粗糙,从而改善界面的黏结特性; 2种纤维的混杂在一定程度上增加了水泥土的无侧限抗压强度,表现出一定的混杂效应,掺入PVA会对混杂系数产生重要影响。     

硅粉对中低掺量水泥土早期强度的影响

以内蒙古河套地区粉质黏土为研究对象,通过对室内掺硅粉水泥土进行的无侧限抗压强度试验,探讨不同硅粉掺量、不同龄期对水泥土无侧限抗压强度的发展规律。试验研究表明:在水泥掺量一定的条件下,硅粉水泥土的无侧限抗压强度基本上是随龄期和硅粉掺量的增加而不断增加,可以明显地提高水泥土的强度。其中硅粉主要起微集料效应和形态效应。     

聚丙烯纤维与水泥固化广州南沙软土的试验研究

为了改善水泥固化软土存在的不足,采用聚丙烯纤维-水泥对广州南沙软土进行固化,分析探讨了纤维水泥固化土的受压破坏方式以及纤维掺量、纤维长度、水泥掺量、龄期对纤维水泥固化土无侧限抗压强度的影响。试验结果表明:在水泥土中掺入纤维能在一定程度上提高其无侧限抗压强度,且在一定范围内,无侧限抗压强度随纤维掺量和纤维长度的增加而增大;纤维水泥土中水泥的最优掺量为12%;纤维水泥土的无侧限抗压强度随着龄期的增长而增大,并且早期强度增长较快,后期增长较慢并趋于稳定;纤维能增加水泥土的抗拉强度,减少水泥土试样破坏时的裂缝宽度和数量,改善它们的脆性破坏形式。     

玻璃纤维水泥土强度及抗硫酸盐侵蚀性能试验研究

通过无侧限抗压强度试验,探究水泥、粉煤灰、玻璃纤维掺量、硫酸盐侵蚀对水泥土抗压强度的影响规律。研究发现:水泥掺量与水泥土抗压强度成正比关系。粉煤灰掺量适当时(不超过6%)可以提高水泥土抗压强度,粉煤灰对水泥土强度增长作用主要在于粉煤灰的微集料效应和活性效应。玻璃纤维掺量为0.2%时,水泥土抗压强度最高,玻璃纤维对水泥土强度的贡献主要在于玻璃纤维的加筋作用。受不同浓度Na2SO4溶液侵蚀作用后,随着侵蚀时间的延长,水泥土抗压强度均先提高后降低。     

掺加纳米SiO_2水泥土力学性能试验研究

通过对掺加纳米SiO_2水泥固化土室内无侧限抗压强度和劈裂强度的试验研究,探索纳米SiO_2对水泥土固化土力学性能的影响。研究结果表明:掺加合适的纳米SiO_2能提高水泥固化土的抗压强度和劈裂强度,随着水泥掺量的增加,无论是否掺加纳米SiO_2,水泥固化土的抗压强度和劈裂强度之间呈线性关系。     

双掺粉煤灰硅粉对水泥土抗压强度影响试验研究

以吉林省延吉市砂土作为研究对象,对双掺硅粉—粉煤灰水泥土进行了无侧限抗压强度试验,分析不同粉煤灰、硅粉掺量以及各龄期对硅粉—粉煤灰水泥土抗压强度的影响,结果表明:随粉煤灰与硅粉掺量的增加,水泥土后期强度基本呈增大趋势,随着粉煤灰掺量的增加,早期抗压强度逐渐减小,后期抗压强度则明显提高,掺硅粉不仅显著改善水泥土早期抗压强度,且明显提高其后期抗压强度。     

污染土对水泥土强度和电阻率影响的试验研究

为揭示污染土对水泥土的影响规律,引入电阻率法作为描述强度和污染特征的手段,分别以3种液体(自来水、生活污水、造纸厂污水)、粉质黏土、两种水泥(普通硅酸盐水泥、矿渣硅酸盐水泥)制作的水泥土为研究对象。首先对比分析3种液体对土体液塑限指标的影响,其次研究不同龄期、水泥类型、污染土类型等条件下水泥土抗压强度和电阻率的变化规律,最后建立电阻率和抗压强度的定量关系。结果表明:污染后土样的液限、塑限均增大,而塑性指数减小;水泥土抗压强度和电阻率均随龄期的增加而呈对数增长;污染土降低了水泥土的抗压强度和电阻率,但是相同龄期下矿渣硅酸盐水泥土的抗压强度和电阻率均高于普通硅酸盐水泥土,说明土体污染后,矿渣水泥对水泥土有一定的抗劣化能力;在不同龄期和污染土条件下,普通硅酸盐水泥土和矿渣硅酸盐水泥土的抗压强度均随着其电阻率线性增长;相比矿渣硅酸盐水泥土,电阻率对普通硅酸盐水泥土更敏感。     

水泥土搅拌桩止水帷幕工程特性研究

水泥土搅拌桩作为基坑止水帷幕已经得到了广泛应用,为了更深入的理解作为止水帷幕的水泥土的工程特性,通过对不同水泥掺入量的水泥土无侧限抗压强度和渗透系数的室内试验研究,利用CBR-1承载比试验仪和TSS-2柔性壁三轴渗透仪对水泥土进行了无侧限抗压强度和渗透试验,分析了养护龄期及水泥掺入量对水泥土的无侧限抗压强度和渗透系数的影响。试验结果表明,水泥土的无侧限抗压强度随养护龄期和水泥掺入量的增大而增大,并通过曲线的拟合,得出了无侧限抗压强度的预测公式;渗透系数随养护龄期和水泥掺入量的增大而减少,通过数据对比得出28天之后水泥土渗透系数主要是受水泥掺入量的影响。     

改善高塑性有机质红黏土强度试验研究

桂林石灰岩地区其基岩面处的红黏土常处于高塑性状态,含有机质时其强度低。通过对高塑性有机质红黏土的加固试验,研究其在有无外加高效减水剂的情况下,水泥掺量、养护时间及水灰比对其无侧限强度的影响。试验表明:高塑性有机质红黏土在水泥加固条件下,其无侧限抗压强度会随着水泥掺量及养护时间的增加而增加,随着水灰比的提高而减小;高效减水剂能明显提高和改善高塑性有机质红黏土的强度力学性质。该试验研究可为红黏土地区的水泥土加固优化设计及施工提供科学依据,以满足实际工程的需要。     

Fibre-reinforced cemented soils compressive and tensile strength assessment as a function of filament length

This study aims to develop a dosage methodology based on tensile and compressive strength for artificially cemented fibre reinforced soils considering filament length. The controlling parameters evaluated were the fibre length (l), the cement content (C), the porosity (η) and the porosity/cement ratio (η/C_iv). A number of unconfined compression and split tensile tests were carried out in the present work. The results show that fibre insertion in the cemented soil, for the whole range of cement content studied, and the increase of reinforcement length improve unconfined compressive and split tensile strengths. It was shown that the porosity/cement ratio, in which volumetric cementitious material content is adjusted by an exponent (0.28 for all the fibre-reinforced and non-reinforced cemented soil mixtures) to end in unique correlations for each mixture, is a good parameter in the evaluation of the unconfined compressive and split tensile strength of the fibre-reinforced and non-reinforced cemented soil studied. Analysis of variance (ANOVA) performed on the results of a factorial experiment considering the effect of adjusted cement content, fibre length and porosity showed that all of these factors are significant in affecting the measured changes in split tensile and unconfined compressive strength values. Finally, unique dosage relationships could be achieved linking the unconfined compressive strength (q_u) and the split tensile strength (q_t) of the sandy soil studied with porosity/cement ratio (η/C_iv) and fibre length (l).     

Effect of fiber-reinforcement on the strength of cemented soils

This study aims to verify the differences in the strength of an artificially cemented sandy soil with and without fiber reinforcement. The controlling parameters evaluated were the amount of cement, porosity, moisture content, and voids/cement ratio. A series of unconfined compression tests and suction measures were carried out. The results show that fiber insertion in the cemented soil, for the whole range of cement studied, causes an increase in unconfined compression strength. The UCS increased linearly with the amount of cement and reduced with the increase in porosity (η) for both the fiber-reinforced and unreinforced specimens. A power function fits well as the relation between unconfined compressive strength (UCS) and porosity (η). Finally, it was shown that the voids/cement ratio is a good parameter in the evaluation of the unconfined compressive strength of the fiber-reinforced and unreinforced cemented soil studied.     

Using fiber and liquid polymer to improve the behaviour of cement-stabilized soft clay

This work studies the effect of using two types of polymer (fibers and liquid) to enhance the strength of cemented soft clay. Four polymer contents were used (0, 0.1, 0.2, 0.5 and 1% by dry weight of the soil) to investigate the unconfined compressive strength, q_un of soft clay mixed with three cement contents (5, 10 and 15%). For wide understanding to the polymer/cemented soil behaviour several factors were considered in this study such as curing time, dry unit weight, the mixture workability and the behaviour after disturbance. This investigation revealed that both fibers and liquid polymers can improve the cemented soft clay strength, however the fiber mechanism in improving the mixture is totally different than the liquid. Increasing the fiber content shall increase q_un till a peak point at fiber content of 0.5%, where the strength started to reduce after. The mixture workability has been improved with increasing the liquid polymer content, and reduced with increasing the fiber content. Fibers can be used to raise up the strength of disturbed cemented soft clay up to 240% by using fiber content of 0.5%. Both fibers and liquid polymers showed a remarkable mechanically, economically and environmentally dominance to be used as additive to cement in improving the soft clay.     

棕榈丝加筋红黏土的无侧限抗压强度研究

红黏土是一种典型的特殊土,土体性质极不稳定,特别是遇水强度快速衰减,容易引发地基沉降或边坡坍塌等工程地质灾害。通过开展棕榈丝改良红黏土的无侧限抗压强度试验,研究不同棕榈丝掺量及长度对红黏土无侧限抗压强度的影响。结果表明,随棕榈丝掺量的增大,棕榈丝加筋土的无侧限抗压强度相应增加;随棕榈丝长度的增大,棕榈丝加筋土的无侧限抗压强度先增大后减小,棕榈丝加筋土的最优棕榈丝长度为20mm。棕榈丝可有效控制土体的变形,提高土体的残余强度。     

High-Strengthening of Cement-Treated Clay by Mechanical Dehydration

A technique called the cement-mixing and mechanical dehydration method (CMD) as one of recycling techniques for soft clay slurry is developed. In order to evaluate the effectiveness of the CMD for increasing the strength of soft clay, a series of unconfined compression tests and several durability tests were performed together with the literature review of unconfined compressive strength in cement-treated soils. Moreover, a series of constant strain rate consolidation tests were also performed to evaluate the effects of cement content and dehydration speed on the permeability of cement-treated clay. The following conclusions are obtained: 1) Literature review and theoretical considerations on the shear strength of cement-treated soils show that an additional treatment for the purpose of increasing the density of cement-treated specimen is effective for increasing the shear strength of cement-treated soil. 2) The mechanical dehydration of soft clay with high pressure is accelerated by cement mixing, where the coefficient of consolidation of cement-treated clay increases as the cement content increases. 3) The high-strength specimen having the unconfined compressive strength of more than 20 MPa can be created from soft clay treated by the CMD with the cement content of over 20% and the dehydration pressure of 20 MPa.     

Role of Fly Ash on Strength and Microstructure Development in Blended Cement Stabilized Silty Clay

This paper presents the role of fly ash on strength and microstructure development in blended cement stabilized silty clay. Its strength was examined by unconfined compression test and its microstructure (fabric and cementation bond) by a scanning electron microscope (SEM), mercury intrusion porosimetry (MIP), and thermal gravity (TG) analysis. The flocculation of clay particles due to the cation exchange process is controlled by cement content, regardless of fly ash content. It increases dry unit weight of the stabilized clay with insignificant change in liquid limit. This results in irrelevant difference in optimum water content (OWC) for the unstabilized and the stabilized clay since OWC of low swelling silty clay is mainly controlled by liquid limit. It is found from the microstructural and the strength test results that the reactivity of fly ash (pozzolanic reaction) is minimal, which is different from concrete technology. This is possibly due to less amount of Ca(OH)₂ to be consumed. The role of fly ash in cement stabilization is to disperse the large clay-cement clusters into smaller clusters. Consequently, the reactive surfaces to be interacted with water increase, and hence the cementitious products (inter-cluster cementation bond). To conclude, the strength development in the blended cement stabilized clay is controlled by cementitious products due to combined effect: hydration and dispersion. Cementitious products due to hydration are governed by cement content, while cementitious products due to dispersion by fly ash content and fineness. Water content of 1.2OWC and 10% replacement ratio are regarded as the effective mixing condition for the stabilization, exhibiting the highest cementitious products.     

红黏土置换作用对水泥固化泥炭土强度的影响

针对红黏土置换后的泥炭土进行了水泥加固试验,并从宏观和微观两个角度对其固化机理展开了分析.研究表明:在含水率一定的条件下,固化泥炭土的无侧限抗压强度随红黏土置换率的提高呈先增大后减小的趋势;红黏土的置换作用一方面能够使其颗粒作为骨架填充固化土体的孔隙,另一方面在减少土体有机质含量的同时增加了Al元素含量,激发水化反应的活性并促进了钙矾石的生成.红黏土置换作用能够使泥炭土的絮状结构变得密实,颗粒连接和孔隙填充得到优化.     

水泥加固酸污染土无侧限强度特征

污染土是利用水泥固化处理后,土体的强度得到提高。针对该项技术,采用水泥固化法处理酸污染土,通过两种试验方案,对水泥加固酸污染土的无侧限抗压强度特性进行研究。试验所用酸污染土用浓硫酸配置人工制备而成,并考虑了不同水泥掺量、不同硫酸浓度和不同龄期对水泥加固酸污染土强度的影响。试验表明:水泥固化酸污染土的强度与水泥掺量和硫酸含量有密切关系,二者共同作用决定其强度的变化。在一定硫酸浓度(2~16g/kg)条件下,伴随硫酸含量的升高,水泥掺量较低时,无侧限抗压强度整体呈明显下降的趋势;水泥掺量较高时,无侧限抗压强度呈缓慢上升的趋势。随着水泥掺量提高,土样的无侧限抗压强度达到峰值时所对应的硫酸含量也逐渐变大。