粉煤灰-剑麻纤维复合改良膨胀土强度及裂隙发育特性  

Strength and cracking characteristics of expansive soil improved by fly ash and sisal fiber

作　　者：郝建斌[1] 张焕 李耕春 刘志云[1] 黄佳欣 蒋臻蔚[1] HAO Jianbin;ZHANG Huan;LI Gengchun;LIU Zhiyun;HUANG Jiaxin;JIANG Zhenwei(School of Geology Engineering and Geomatics,Chang’an University,Xi’an 710054,China)

机构地区：[1]长安大学地质工程与测绘学院,陕西西安710054

出　　处：《铁道科学与工程学报》2022年第9期2620-2628,共9页Journal of Railway Science and Engineering

基　　金：国家自然科学基金资助项目(41472266,42077260);中央高校基金资助项目(300102262204)。

摘　　要：为研究粉煤灰-剑麻纤维复合改良膨胀土的效果和机理,以汉中某地膨胀土为研究对象,分别开展了素膨胀土、粉煤灰改良土和粉煤灰-剑麻纤维复合改良土的无侧限抗压强度试验和干湿循环试验。试验结果表明:粉煤灰改良土和粉煤灰-剑麻纤维复合改良土均能有效提高土体的无侧限抗压强度和抗变形能力,但复合改良效果更好,且最优配比为:粉煤灰质量含量9%,剑麻纤维质量含量0.4%,长度20 mm。无侧限抗压强度试验中,素土和粉煤灰改良土试样均出现明显的宏观剪切破裂面,而复合改良土试样呈近似“塑性鼓胀破坏”特征,出现剪切破裂带。多次干湿循环后,素土发育的裂隙具有直、宽、长的特征,粉煤灰改良土和复合改良土发育的裂隙具有细、密、短的特征,其中复合改良土发育的裂隙最细小且再次吸湿后易闭合。相同干湿循环次数下,3种试样的表面裂隙率大小关系为:复合改良土<粉煤灰改良土<素土,说明膨胀土中掺入粉煤灰和剑麻纤维能有效抑制裂隙的发育及扩展,采用粉煤灰-剑麻纤维改良膨胀土是可行的。研究结论可为膨胀土路基工程和边坡防护等工程中的设计和施工提供参考。To study the effect and mechanism of fly ash and sisal fiber composite improved expansive soil,taking expansive soil in Hanzhong as the research object,the unconfined compressive strength tests and dry-wet cycling tests of plain expansive soils,fly ash improved soils and composite improved soils were carried out respectively.The tests show that adding fly ash alone and adding fly ash and sisal fiber can effectively improve the unconfined compressive strength and deformation resistance of soil,but the composite improved expansive soil has better effect.The optimal ratio is as follows.The content of fly ash is 9%,the content of sisal fiber is 0.4%,and the length of sisal fiber is 20 mm.In the unconfined compressive strength tests,both plain soil and fly ash improved soil samples showed obvious macro shear fracture surface,while the composite improved soil samples showed the characteristics of“plastic swelling failure”and shear fracture zone.After several dry-wet cycles,the cracks of plain soil were straight,wide and long,and the cracks of fly ash improved soil and composite soil were slim,dense and short.And the cracks of composite improved soil were the smallest and easy to close after moisture absorption.The relationship between the crack rate of the three soils is as follows.Composite improved soil<fly ash improved soil<plain soil.This indicats that adding fly ash and sisal fiber to expansive soil can effectively inhibit the development and expansion of cracks.It is feasible to use fly ash and sisal fiber to improve expansive soil.The results of this paper can provide reference for the design and construction of expansive soil subgrade engineering and slope protection.

关 键 词：膨胀土 粉煤灰 剑麻纤维 裂隙特性 干湿循环 

分 类 号：TU443[建筑科学—岩土工程]