麦秸秆加筋土的强度特性及细观结构分析
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摘要
为了分析麦秸秆加筋对土体抗剪强度的影响,开展了4种加筋率(0.1%,0.2%,0.3%,0.4%)和3种加筋长度(5,10,15 mm)下的三轴剪切试验.通过CT(计算机断层扫描)扫描图像,对比分析了加筋土和素土在加载过程中的细观结构变化.结果表明:麦秸秆加筋黏性土的抗剪强度和抗变形能力较素土都有显著提高,其中筋材长度为10 mm时加筋效果较好.所研究加筋条件下,土体黏聚力较素土黏聚力增大0.1～2.3倍,内摩擦角变化在±2°范围内.与素土相比,加筋土在剪切过程中无明显的宏观剪切破坏,均为鼓胀破坏.围压较小时,加筋作用明显,对土体的刚度影响较大,随着围压的增大,影响逐渐变小.CT扫描结果显示,麦秸秆加筋能够限制土体变形和裂纹扩展.因此,麦秸秆适宜作为黏性土的加筋材料.
This study presents results of an laboratory triaxial experimental program with respect to study the effect of wheat straw reinforcement on the shear strength of soil. Three-axis shear tests were carried out under four reinforcement rates(0.1%, 0.2%, 0.3%, 0.4%) and three reinforced lengths(5, 10, 15 mm). The mesostructure changes of reinforced soil and plain soil during loading are compared and analyzed by using computed tomography(CT) scan image. The results show that: the shear strength and deformation resistance of wheat straw reinforced soil are significantly improved than plain soil, and the reinforcement effect is better when the wheat straw length is 10 mm.In this condition, the cohesive forces of reinforced soil are 1.1 to 3.3 times that of unreinforced soil, the internal friction angle changes in the range of ±2 degrees. Compared with plain soil, the macroscopic shear failure of reinforced soil during shearing is not obvious, and all of them are bulging failure. When the confining pressure is small, the effect of reinforcement is significant, and the effect on the stiffness of soil is fine. With the increase of confining pressure, the effect becomes weaker. CT scanning results show that wheat straw reinforcement can restrict soil deformation and crack growth. It is concluded from this study that wheat straws are a suitable reinforced material for cohesive soil.
This study presents results of an laboratory triaxial experimental program with respect to study the effect of wheat straw reinforcement on the shear strength of soil. Three-axis shear tests were carried out under four reinforcement rates(0.1%, 0.2%, 0.3%, 0.4%) and three reinforced lengths(5, 10, 15 mm). The mesostructure changes of reinforced soil and plain soil during loading are compared and analyzed by using computed tomography(CT) scan image. The results show that: the shear strength and deformation resistance of wheat straw reinforced soil are significantly improved than plain soil, and the reinforcement effect is better when the wheat straw length is 10 mm.In this condition, the cohesive forces of reinforced soil are 1.1 to 3.3 times that of unreinforced soil, the internal friction angle changes in the range of ±2 degrees. Compared with plain soil, the macroscopic shear failure of reinforced soil during shearing is not obvious, and all of them are bulging failure. When the confining pressure is small, the effect of reinforcement is significant, and the effect on the stiffness of soil is fine. With the increase of confining pressure, the effect becomes weaker. CT scanning results show that wheat straw reinforcement can restrict soil deformation and crack growth. It is concluded from this study that wheat straws are a suitable reinforced material for cohesive soil.
引文
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[14] 卢浩,晏长根,杨晓华,等.麦秆纤维加筋土的抗冲蚀性及其防护效果试验研究[J].铁道科学与工程学报,2017,14(10):2138.LU Hao,YAN Changgen,YANG Xiaohua,et al.Experimental research on anti-eroding property and protection effect of reinforced soil with straw fibers[J].Journal of Railway Science and Engineering,2017,14(10):2138.
[15] 余沛,柴寿喜,王晓燕,等.麦秸秆加筋滨海盐渍土的加筋效应及工程应用问题[J].天津城市建设学院学报,2010,16(3):161.YU Pei,CHAI Shouxi,WANG Xiaoyan,et al.Reinforcement effect and engineering application problems of littoral saline soil reinforced with wheat straw[J].Journal of Tianjin Institute of Urban Construction,2010,16(3):161.
[2] 徐超,贾斌,罗玉珊,等.圬工与加筋土组合式挡墙离心模型试验[J].同济大学学报(自然科学版),2015,43(3):379.XU Chao,JIA Bin,LUO Yushan,et al.Centrifuge model tests of behavior of masonry and reinforced soil composite retaining wall[J].Journal of Tongji University(Natural Science),2015,43(3):379.
[3] 唐朝生,施斌,顾凯.纤维加筋土中筋/土界面相互作用的微观研究[J].工程地质学报,2011,19(4):610.TANG Chaosheng,SHI Bin,GU Kai.Microstructural study on interfacial interactions between fiber reinforcement and soil[J].Journal of Engineering Geology,2011,19(4):610.
[4] 施利国,张孟喜,曹鹏.聚丙烯纤维加筋灰土的三轴强度特性[J].岩土力学,2011,32(9):2721.SHI Liguo,ZHANG Mengxi,CAO Peng.Triaxial shear strength characteristics of lime-soil reinforced with polypropylene fiber inclusions[J].Rock and Soil Mechanics,2011,32(9):2721.
[5] TANG Chaosheng,SHI Bin,CUI Yujun,et al.Desiccation cracking behavior of polypropylene fiber–reinforced clayey soil[J].Canadian Geotechnical Journal,2012,49(9):1088.
[6] ANAGNOSTOPOULOS C,TZETZIS D,BERKETIS K.Shear strength behaviour of polypropylene fibre reinforced cohesive soils[J].Geomechanics and Geoengineering,2014,9(3):241.
[7] CHEGENIZADEH A,NIKRAZ H.Effective parameters on strength of fibre reinforced soil[J].Applied Mechanics and Materials,2012,166-169(1):1630.
[8] 吴燕开,牛斌,桑贤松.随机分布剑麻纤维加筋土力学性能试研究[J].水文地质工程地质,2012,39(6):77.WU Yankai,NIU Bin,SANG Xiansong.Experimental study of mechanical properties of soil randomly included with sisal fiber[J].Engineering Geology of Hydrogeology,2012,39(6):77.
[9] 钱叶琳,王洁,吕卫柯,等.黄麻纤维加筋土的强度特性及增强机理研究[J].河北工程大学学报(自然科学版),2016,33(2):19.QIAN Yelin,WANG Jie,LV Weike,et al.Research on strength characteristics and improving mechanism of Jute fiber-reinforced soil [J].Journal of Hebei University of Engineering(Natural Science),2016,33(2):19.
[10] 王元战,刘旭菲,张智凯,等.含根量对原状与重塑草根加筋土强度影响的试验研究[J].岩土工程学报,2015,37(8):1405.WANG Yuanzhan,LIU Xufei,ZHANG Zhikai,et al.Experimental research on influence of root content on strength of undisturbed and remolded grassroots-reinforced soil[J].Chinese Journal of Geotechnical Engineering,2015,37(8):1405.
[11] 李敏,柴寿喜,魏丽.麦秸秆的力学性能及加筋滨海盐渍土的抗压强度研究[J].工程地质学报,2009,17(4):545.LI Min,CHAI Shouxi,WEI Li.Mechanical properties of wheat straw and strength of its reinforced inshore saline soil[J].Journal of Engineering Geology,2009,17(4):545.
[12] 魏丽,柴寿喜,蔡宏洲,等.麦秸秆的物理力学性能及加筋盐渍土的抗压强度[J].土木工程学报,2010,43(3):93.WEI Li,CHAI Shouxi,CAI Hongzhou,et al.Physical and mechanical properties of wheat straw and unconfined compressive strength of reinforced inshore saline soil with wheat straw[J].China Civil Engineering Journal,2010,43(3):93.
[13] 璩继立,俞汉宁,江海洋,等.棕榈丝与麦秸秆丝加筋土无侧限抗压强度比较[J].地下空间与工程学报,2015,11(5):1216.QU Jili,YU Hanning,JIANG Haiyang,et al.Comparison of unconfined compressive strength of soil reinforced by palm fiber or wheat straw fiber[J].Chinese Journal of Underground Space and Engineering,2015,11(5):1216.
[14] 卢浩,晏长根,杨晓华,等.麦秆纤维加筋土的抗冲蚀性及其防护效果试验研究[J].铁道科学与工程学报,2017,14(10):2138.LU Hao,YAN Changgen,YANG Xiaohua,et al.Experimental research on anti-eroding property and protection effect of reinforced soil with straw fibers[J].Journal of Railway Science and Engineering,2017,14(10):2138.
[15] 余沛,柴寿喜,王晓燕,等.麦秸秆加筋滨海盐渍土的加筋效应及工程应用问题[J].天津城市建设学院学报,2010,16(3):161.YU Pei,CHAI Shouxi,WANG Xiaoyan,et al.Reinforcement effect and engineering application problems of littoral saline soil reinforced with wheat straw[J].Journal of Tianjin Institute of Urban Construction,2010,16(3):161.