Evaporation process and tensile behavior of fiber-reinforced rammed earth
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摘要: 土坯作为一种生态、低碳和环保的建筑材料,其力学性能是学界和工程技术人员关注的重点。为了提高土坯的综合抗拉特性,提出采用纤维加筋技术对土坯进行改性处理。通过模拟土坯的形成过程,制备了一系列不同纤维掺量（0～0.2%）、初始含水率（16.5%～20.5%）和干密度（1.50～1.70 g/cm3）的压实土坯试样,进行自然干燥处理,并对干燥后的土坯试样开展了一系列劈裂试验,重点分析了纤维掺量和初始压实状态对土坯干燥失水过程及抗拉强度的影响。结果表明：①纤维加筋对土坯的干燥失水过程没有明显影响,但加筋土坯的残余含水率随纤维掺量呈“先降后升”趋势；②纤维加筋能显著提高土坯的抗拉强度,但其对抗拉强度的贡献随掺量的参加呈“先升后缓”趋势,对南京地区的下蜀土而言,其最优纤维掺量为0.1%,且纤维加筋能有效抑制土坯的脆性破坏模式,改善土坯的残余抗拉强度和韧性；③提高土坯制作时的初始含水率和初始干密度对改善土坯的抗拉强度和纤维加筋效果有较好的正面作用；④纤-土界面的微观力学作用及纤维的“桥梁”作用是控制纤维加筋土坯综合抗拉特性的关键因素。Abstract: The rammed earth is an environmental-friendly building material. Its mechanical properties draw lots of attention among researchers and engineers in recent years. In order to improve the tensile performance of the rammed earth, the fiber-reinforcement is applied to better modify its properties. A series of compacted rammed earth samples with different fiber contents (0~0.2%), initial water contents (16.5%~20.5%) and dry densities (1.5~1.7 g/cm3) are prepared by simulating the natural air-drying process of rammed earthmaking. The splitting tensile tests are carried out on the air-dried rammed earth samples. The effects of fiber content and initial state on the evaporation process and tensile strength of rammed earth are analyzed. The results show that: (1) The fiber content has few influences on the evaporation rate of the reinforced rammed earth. But with the increase of the fiber content, the residual moisture content of the reinforced rammed earth decreases first and then increases. (2) The fiber inclusion can significantly improve the tensile strength of the rammed earth, but the contribution of fiber reinforcement to strength increment will be reduced beyond a certain fiber content. The optimum fiber content for Xiashu soil in Nanjing area is observed at 0.1%. The fiber inclusion can also modify the brittle failure mode of the rammed earth to ductile one so as to improve the residual tensile strength and toughness of the rammed earth. (3) Increase of the initial water content and the initial dry density can significantly improve the tensile strength and the fiber reinforcement benefit. (4) The micromechanical interaction of the fiber-soil interface and the "bridging" effect of the fiber are the key factors controlling the overall tensile behavior of the fiber-reinforced rammed earth.
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Keywords:
- rammed earth /
- fiber-reinforced soil /
- drying evaporation /
- tensile strength /
- water content /
- dry density
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图 2 不同纤维掺量试样平均含水率随时间变化
Figure 2. Variation of average water content versus time for samples with different fiber contents
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图 3 不同纤维掺量试样相对蒸发速率随时间变化
Figure 3. Variation of relative evaporation rate (Ea/Ep) versus time for samples with different fiber contents
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图 4 不同纤维掺量试样残余含水率
Figure 4. Residual water contents of samples with different fiber contents
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图 5 不同初始含水率试样蒸发过程
Figure 5. Evaporation process of samples with different initial water contents
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图 6 不同初始干密度试样蒸发过程
Figure 6. Evaporation process of samples with different initial dry densities
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图 8 纤-土界面作用示意图
Figure 8. Schematic diagram of interfacial mechanical interaction between soil particles and fiber
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图 9 不同初始状态下纤-土界面作用示意图
Figure 9. Schematic diagram of structure of fiber-reinforced rammed earth under different initial conditions
表 1 南京地区下蜀土基本物理性质
Table 1 Basic physical properties of Xiashu soil in Nanjing area
相对质量密度GS 液限wL/% 塑限wP/% 塑性指数IP 最大干密度ρd/(g·cm-3) 最优含水率wopt/% 2.71 34.5 18.4 17 1.70 16.5 
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表 2 聚丙烯纤维基本物理力学性质
Table 2 Physical and mechanical properties of polypropylene fiber
密度/(g·cm-3) 直径/mm 长度/mm 抗拉强度/MPa 弹性模量/MPa 熔点/℃ 燃点/℃ 0.91 0.048 12 ≥350 ≥3500 165 590
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表 3 各组试样的参数
Table 3 Parameters of different sets of samples
试样编号 纤维掺量/% 初始含水率/% 压实干密度/(g·cm-3) T1 0 16.5 1.70 T2 0.05 16.5 1.70 T3 0.10 16.5 1.70 T4 0.15 16.5 1.70 T5,S1 0.20 16.5 1.70 S2 0.20 18.5 1.70 S3,G1 0.20 20.5 1.70 G2 0.20 20.5 1.60 G3 0.20 20.5 1.50
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[1] PACHECO-TORGAL F, JALALI S. Earth construction: Lessons from the past for future eco-efficient construction[J]. Construction and Building Materials, 2012, 29: 512-519. doi: 10.1016/j.conbuildmat.2011.10.054
[2] HALL M, DJERBIB Y. Rammed earth sample production: context, recommendations and consistency[J]. Construction and Building Materials, 2004, 18(4): 281-286. doi: 10.1016/j.conbuildmat.2003.11.001
[3] 刘军, 袁大鹏, 周红红, 等. 狗尾草对加筋土坯力学性能的影响[J]. 沈阳建筑大学学报(自然科学版), 2010, 26(4): 720-723, 733. https://www.cnki.com.cn/Article/CJFDTOTAL-SYJZ201004022.htm LIU Jun, YUAN Da-peng, ZHOU Hong-hong, et al. Impact of green bristle grass on mechanical properties of reinforced rammed earth[J]. Journal of Shenyang Jianzhu University (Natural Science), 2010, 26(4): 720-723, 733. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-SYJZ201004022.htm
[4] EASTON D. The Rammed Earth House[M]. Vermont: Chelsea Green Publishing Company, 2007: 1-42.
[5] KOUAKOUC H, MORELJ C. Strength and elasto-plastic properties of non-industrial building materials manufactured with clay as a natural binder[J]. Applied Clay Science, 2009, 44(1/2): 27-34.
[6] SILVEIRA D, VARUM H, ANÍBAL Costa, et al. Mechanical properties of rammed earth bricks in ancient constructions[J]. Construction and Building Materials, 2012, 28(1): 36-44. doi: 10.1016/j.conbuildmat.2011.08.046
[7] JAQUIN P A, AUGARDE C E, GALLIPOLI D, et al. The strength of unstabilised rammed earth materials[J]. Géotechnique, 2009, 59(5): 487-490. doi: 10.1680/geot.2007.00129
[8] BUI Q B, MOREL J C, HANS S, et al. Effect of moisture content on the mechanical characteristics of rammed earth[J]. Construction and Building materials, 2014, 54: 163-169. doi: 10.1016/j.conbuildmat.2013.12.067
[9] BECKETT C, CIANCIO D. Effect of compaction water content on the strength of cement-stabilized rammed earth materials[J]. Canadian Geotechnical Journal, 2014, 51(5): 583-590. doi: 10.1139/cgj-2013-0339
[10] EL-NABOUCH R, BUI Q B, PLÉ O, et al. Characterizing the shear parameters of rammed earth material by using a full-scale direct shear box[J]. Construction and Building Materials, 2018, 171: 414-420. doi: 10.1016/j.conbuildmat.2018.03.142
[11] ARAKI H, KOSEKI J, SATO T. Tensile strength of compacted rammed earth materials[J]. Soils and Foundations, 2016, 56(2): 189-204. doi: 10.1016/j.sandf.2016.02.003
[12] 谢约翰, 唐朝生, 尹黎阳, 等. 纤维加筋微生物固化砂土的力学特性[J]. 岩土工程学报, 2019, 41(4): 675-682. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201904014.htm XIE Yue-han, TANG Chao-sheng, YIN Li-yang, et al. Mechanical behavior of microbial-induced calcite precipitation (MICP) - treated soil with fiber reinforcement[J]. Chinese Journal of Geotechnical Engineering, 2019, 41(4): 675-682. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201904014.htm
[13] TANG C S, WANG D Y, CUI Y J, et al. Tensile strength of fiber-reinforced soil[J]. Journal of Materials in Civil Engineering, 2016, 28(7): 04016031. doi: 10.1061/(ASCE)MT.1943-5533.0001546
[14] 唐朝生, 施斌, 高玮, 等. 纤维加筋土中单根纤维的拉拔试验及临界加筋长度的确定[J]. 岩土力学, 2009, 30(8): 2225-2230. doi: 10.3969/j.issn.1000-7598.2009.08.004 TANG Chao-sheng, SHI Bin, GAO Wei, et al. Single fiber pull-out test and the determination of critical fiber reinforcement length for fiber reinforced soil[J]. Rock and Soil Mechanics, 2009, 30(8): 2225-2230. (in Chinese) doi: 10.3969/j.issn.1000-7598.2009.08.004
[15] PATEL S K, SINGH B. Strength and deformation behavior of fiber-reinforced cohesive soil under varying moisture and compaction states[J]. Geotechnical and Geological Engineering, 2017, 35(4): 1767-1781. doi: 10.1007/s10706-017-0207-y
[16] CONSOLI N C, BASSANI M A A, FESTUGATO L. Effect of fiber-reinforcement on the strength of cemented soils[J]. Geotextiles and Geomembranes, 2010, 28(4): 344-351. doi: 10.1016/j.geotexmem.2010.01.005
[17] 王德银, 唐朝生, 李建, 等. 纤维加筋非饱和黏性土的剪切强度特性[J]. 岩土工程学报, 2013, 35(10): 1933-1940. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201310029.htm WANG De-yin, TANG Chao-sheng, LI Jian, et al. Shear strength characteristics of fiber-reinforced unsaturated cohesive soils[J]. Chinese Journal of Geotechnical Engineering, 2013, 35(10): 1933-1940. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201310029.htm
[18] TANG C S, SHI B, GAO W, et al. Strength and mechanical behavior of short polypropylene fiber reinforced and cement stabilized clayey soil[J]. Geotextiles and Geomembranes, 2007, 25(3): 194-202. doi: 10.1016/j.geotexmem.2006.11.002
[19] TANG C S, SHI B, ZHAO L Z. Interfacial shear strength of fiber reinforced soil[J]. Geotextiles and Geomembranes, 2010, 28(1): 54-62. doi: 10.1016/j.geotexmem.2009.10.001
[20] AN N, TANG C S, XU S K, et al. Effects of soil characteristics on moisture evaporation[J]. Engineering Geology, 2018, 239: 126-135. doi: 10.1016/j.enggeo.2018.03.028
[21] FRYDMAN S. Applicability of the Brazilian (indirect tension) test to soils[J]. Australian Journal of Applied Science, 1964, 15(4): 335-343.
[22] 王德银, 唐朝生, 李建, 等. 纤维加筋非饱和黏性土的剪切强度特性[J]. 岩土工程学报, 2013, 35(10): 1933-1940. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201310029.htm WANG De-yin, TANG Chao-sheng, LI Jian, et al. Shear strength characteristics of fiber-reinforced unsaturated cohesive soils[J]. Chinese Journal of Rock Mechanics and Engineering, 2013, 35(10): 1933-1940. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201310029.htm
[23] HILLEL D. Introduction to Environmental Soil Physics[M]. Massachusetts: Academic Press, 2003: 337-361.
[24] MILLERC J, RIFAI S. Fiber Reinforcement for waste containment soil liners[J]. Journal of Environmental Engineering, 2004, 130(8): 891-895. doi: 10.1061/(ASCE)0733-9372(2004)130:8(891)
[25] DELAGE P, AUDIGUIER M, CUI Y J, et al. Microstructure of a compacted silt[J]. Canadian Geotechnical Journal, 1996, 33(1): 150-158. doi: 10.1139/t96-030
[26] CHADUVULA U, VISWANADHAM B V S, KODIKARA J. A study on desiccation cracking behavior of polyester fiber-reinforced expansive clay[J]. Applied Clay Science, 2017, 142: 163-172.
[27] MILLOGO Y, MOREL J C, AUBERT J E, et al. Experimental analysis of pressed rammed earth blocks reinforced with Hibiscus cannabinus fibers[J]. Construction and Building Materials, 2014, 52: 71-78.
[28] TANG C S, SHI B, GAO W, et al. Strength and mechanical behavior of short polypropylene fiber reinforced and cement stabilized clayey soil[J]. Geotextiles and Geomembranes, 2007, 25(2): 194-202.
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