冻融循环对二灰和改性聚乙烯醇固化盐渍土力学性能的影响

随季节性变化的冻融循环作用对土体结构有显著的影响。为降低盐渍土对环境温度的敏感性并将其应用于工程中,提出以石灰、粉煤灰和改性聚乙烯醇(MPA)为固化材料的联合固化方法。先通过无侧限抗压强度(UCS)和微观扫描试验评价固化效果,构建固化材料的参数范围,再将抗剪强度(黏聚力和内摩擦角)与正交试验相结合,分析各因素的影响,明确最佳组合参数。结果表明:石灰+粉煤灰+MPA联合固化有助于提高盐渍土的强度,联合固化盐渍土的UCS为1 130.25 kPa,是盐渍土(218 k Pa)的5.18倍;联合固化盐渍土的冻融强度满足工程规范(JTG 3430-2020)要求。冻融循环作用下联合固化盐渍土的UCS稳定值为700k Pa,且3次循环后的波动范围在5%左右。适宜配比下联合固化盐渍土的抗剪强度(黏聚力和内摩擦角)在3次冻融循环后为208.2 kPa和38.56°。各因素的敏感性由高到低依次为养护时间、石灰掺量、MPA掺量、干密度、含盐量和冻融循环次数,随石灰、粉煤灰和MPA掺量的增加,联合固化盐渍土强度增大并趋于稳定,固化参数的优化可有效弱化冻融作用对滨海盐渍土的影响。结合抗压及抗剪强度试验结果,...

Mechanical properties of saline soil solidified with the mixture of lime,fly ash and modified polyvinyl alcohol under freeze-thaw cycles

The repeated freeze-thaw cycles with seasonal alternations have an obvious effect on soil structure. To reduce the sensitivity of saline soil to temperature and then use it in engineering, a combined treatment method is proposed, where lime, fly ash and modified polyvinyl alcohol(MPA) are used as solidified materials. Unconfined compressive strength(UCS) and microstructure characterization tests are firstly used to evaluate the solidified effect and obtain the parameters scope of solidified materials. Then the tests of shear strength(cohesion and internal friction angle) and the orthogonal experiment are used to analyze the influence of each factor, and then obtained the optimal combination of solidified parameters. The results indicate that the combination of lime, fly ash and MPA can improve the strength of saline soil. After combined treatment, the UCS is 1 130.25 kPa, which is 5.18 times than that of saline soil(218 kPa). The strength of combined solidified saline soil meets the requirements of engineering specification(JTG 3430-2020). The stable value of UCS of combined solidified saline soil under freeze-thaw cycles is 700 kPa. The fluctuation is about 5%after three freeze-thaw cycles. The cohesion and the internal friction angle of combined solidified saline under the most appropriate ratio can be 208.2 kPa and 38.56°, respectively after three freezing-thawing cycles. The sensitivity ranking of the factors is as follows:curing time, lime content, MPA content, dry density, salt content, and times of freeze-thaw cycles. With an increase in lime, fly ash and MPA content, the strength of combined solidified saline soil increases and then tends to become stable. The optimization of solidification parameters can effectively weaken the influence of freeze-thaw on coastal saline soil. Based on tests results of compressive strength and shear strength, it can be concluded that the optimal combination of solidified parameters is 14% of lime,30% of fly ash, 1% of MPA, 28 days of curing time, and a dry density of 1.65 g/cm³.