盐渍土的盐胀溶陷等不良工程特性对交通基础设施建设及其安全运行有着极其不利影响。现以南疆地区路基氯盐渍土为研究对象,开展了不同龄期改良氯盐渍土2种试验方案的无侧限抗压强度试验及SEM-EDS试验,研究水玻璃、水泥、石灰、粉煤灰及纤维等多种材料联合改良盐渍土的机理及其微观特征。研究结果表明:以28 d抗压强度作为评价标准,方案1中最优组合为水泥8%+石灰12%+纤维0.2%+纤维长度18 mm+含盐量3%,适用于中盐渍土改良;方案2中最优组合为粉煤灰20%+石灰6%+纤维0.2%+纤维长度12 mm+含盐量1%,适用于弱盐渍土改良。2种方案改良盐渍土越过应力峰值后仍能保持较高的抗压强度值,改良盐渍土应力-应变曲线呈应变软化型,试样呈脆性破坏。根据微观结构及EDS分析,改良盐渍土的矿物颗粒相对较大,颗粒完整性较好,胶凝物由絮状水化硅酸钙和针状钙矾石构成,其微观结构较致密,颗粒间接触方式以面-面接触方式为主;相比方案2,方案1内部结构排列致密,内部完整性好,强度性能优越。该研究成果丰富了氯盐渍土改良技术,为盐渍土在路基处理中再循环利用提供了技术参考。
Abstract
The unfavorable engineering characteristics of saline soil such as salt expansion and solution subsidence have extremely adverse effects on the construction of transportation infrastructure and its safe operation. The mechanism of improving saline soil by adding sodium silicate, cement, lime, fly ash and fiber and the microscopic characteristics of improved soil were investigated via unconfined compression test and SEM-EDS test on the chloride saline soil of subgrade in south Xinjiang. Results manifest that with the 28 d compressive strength as the evaluation standard, the optimal combination in scheme 1 (cement content 8%, lime content 12%, fiber content 0.2%, and fiber length 18 mm, with a salt content of 3%) is suitable for improving medium chloride saline soil; the optimal combination in scheme 2 (fly ash content 20%, lime content 6%, fiber content 0.2%, and fiber length 12 mm, with a salt content of 1%) is suitable for improving weak chlorine saline soil. The improved saline soil modified by the aforementioned two schemes could both retain high compressive strength after reaching stress peak, and the stress-strain curves display strain softening feature with brittle failure. Microstructure and EDS analysis illustrate that the mineral particles of the modified and solidified saline soil are relatively large with sound particle integrity. The cementitious material is composed of flocculent calcium silicate hydrate and acicular ettringite with dense microstructure. The contact mode between particles is mainly face-to-face contact. Compared with those in scheme 2, the improved soil specimen in scheme 1 is of dense internal structure, good internal integrity, and superior strength performance.
关键词
盐渍土 /
正交试验 /
无侧限抗压强度 /
微观特性 /
SEM-EDS
Key words
chloride saline soil /
orthogonal test /
unconfined compressive strength /
microscopic characteristics /
SEM-EDS test
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参考文献
[1] 温利强. 我国盐渍土的成因及分布特征[D]. 合肥:合肥工业大学, 2010.
[2] 牛玺荣, 李志农, 高江平. 盐渍土盐胀特性与机理研究进展[J]. 土壤通报, 2008(1):163-168.
[3] 李 敏, 王 宸, 杜红普, 等. 石灰粉煤灰联合固化石油污染滨海盐渍土的力学特性[J]. 岩石力学与工程学报, 2017,36(增刊1):3578-3586.
[4] 刘诚斌, 纪洪广, 刘娟红, 等. 矿渣复合胶凝材料固化滨海盐渍土的试验研究[J]. 建筑材料学报, 2015,18(1):82-87.
[5] 柴寿喜. 固化滨海盐渍土的强度特性研究[D]. 兰州:兰州大学, 2006.
[6] 柴寿喜, 王晓燕, 王 沛, 等. 六种固化滨海盐渍土的轴向应力应变特征[J]. 辽宁工程技术大学学报(自然科学版), 2009,28(6):941-944.
[7] MIN L, SHOU X C, HU Y Z,et al. Feasibility of Saline Soil Reinforced with Treated Wheat Straw and Lime[J]. Soils and Foundations,2012,52(2):228-238.
[8] 范礼彬, 章定文, 邓永锋, 等. 氯盐对水泥固化土应力应变特性影响分析[J]. 工程地质学报, 2012,20(4):621-626.
[9] 宫经伟, 王 亮, 慈 军, 等. 硫酸盐含量对全固废材料固化盐渍土抗压强度的影响[J]. 长江科学院院报, 2021,38(2):73-79.
[10] ZHANG Sha-sha, YANG Xiao-hua, XIE Shan-jie, et al. Experimental Study on Improving the Engineering Properties of Coarse Grain Sulphate Saline Soils with Inorganic Materials[J]. Cold Regions Science and Technology, 2020, 170: 1-10.
[11] 吕擎峰, 申 贝, 王生新, 等. 水玻璃固化硫酸盐渍土强度特性及固化机制研究[J]. 岩土力学, 2016,37(3):687-693.
[12] LV Qing-feng, JIANG Lu-sha, MA Bo, et al. A Study on the Effect of the Salt Content on the Solidification of Sulfate Saline Soil Solidified with an Alkali-activated Geopolymer[J]. Construction and Building Materials, 2018, 176:68-74.
[13] 吕擎峰, 孟惠芳, 王生新, 等. 改性水玻璃固化盐渍土强度及冻融循环耐久性试验研究[J]. 北京工业大学学报, 2017,43(1):108-112.
[14] 王 琦. 石灰-纤维改良盐渍土的路用性能研究[D]. 长春:吉林大学, 2019.
[15] 贺生云, 李宏波, 吴振华, 等. 粉煤灰-镁渣改良超盐渍土的工程性质研究[J]. 科学技术与工程, 2015,15(22):176-180.
[16] 于 新, 孙 强. 水泥石灰改良氯盐渍土强度特性试验研究[J]. 华东交通大学学报, 2011,28(5):29-34.
基金
新疆维吾尔自治区自然科学基金项目(2018D01B02)
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