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Journal of ZheJiang University (Engineering Science)  2022, Vol. 56 Issue (1): 111-117    DOI: 10.3785/j.issn.1008-973X.2022.01.012
    
Deformation characteristics of fiber-reinforced foam lightweight soil under cyclic loading and unloading
Jiang-bo XU1,2,3(),Yuan-zhi WANG1,Yu QI1,Bao-hua CAO1,Yong-zhen LUO1,Chang-gen YAN1,Xiao-hua YANG1,Han BAO1,Yu-zhou XIANG4
1. Highway School, Chang’an University, Xi’an 710064, China
2. National Local Joint Engineering Laboratory for Road Engineering and Disaster Prevention and Reduction Technology in Mountainous Areas, Chongqing 400067, China
3. China Electronic Research Institute of Engineering Investigations and Design, Xi’an 710064, China
4. Chongqing Chengtou Road and Bridge Administration Limited Company, Chongqing 400015, China
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Abstract  

The UNSAT unsaturated soil triaxial instrument was used to conduct cyclic loading and unloading tests under 50 kPa confining pressure in order to analyze the damage and deformation characteristics of polypropylene fiber-reinforced foamed lightweight soil. The mechanical properties and deformation laws of polypropylene fiber reinforced foam lightweight soil under different fiber mass fraction conditions were analyzed by using Poisson’s ratio, elastic modulus increase rate and elastic-plastic deformation trend as parameters. The research results showed that the initial elastic modulus increase rate was 56.88%-69.43% when the fiber mass fraction reached 0.50% to 1.00%. The fiber has the best effect on improving the initial defects of the foamed lightweight soil. The elastic modulus increase rate of the fiber-reinforced foamed lightweight soil sample firstly increases and then decreases with the increase of the number of cycles. The Poisson’s ratio increases with the increase of the number of cycles, and tends stable after the first 2 and 3 cycles of loading until the sample is broken. The ratio of the axial elastic strain to the total strain of the fiber-reinforced foam lightweight soil gradually decreases as the number of cycles increases, and the internal damage and deformation of the sample gradually accumulate.



Key wordsfiber-reinforced foam lightweight soil      cyclic loading and unloading      elastic modulus      damage deformation      Poisson’s ratio     
Received: 06 March 2021      Published: 05 January 2022
CLC:  U 416  
Fund:  国家重点研发计划资助项目(2016YFC0802203-8);长安大学中央高校基本科研业务费专项资金资助项目(300102219213);国家自然科学基金资助项目(41790443);陕西省重点研发计划资助项目(2018ZDXM-SF-024);中国博士后科学基金资助项目 (2020M683244)
Cite this article:

Jiang-bo XU,Yuan-zhi WANG,Yu QI,Bao-hua CAO,Yong-zhen LUO,Chang-gen YAN,Xiao-hua YANG,Han BAO,Yu-zhou XIANG. Deformation characteristics of fiber-reinforced foam lightweight soil under cyclic loading and unloading. Journal of ZheJiang University (Engineering Science), 2022, 56(1): 111-117.

URL:

https://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2022.01.012     OR     https://www.zjujournals.com/eng/Y2022/V56/I1/111


循环加卸载下纤维增强泡沫轻质土变形特性

为了研究聚丙烯纤维增强泡沫轻质土的损伤变形特性,选用UNSAT非饱和土三轴仪开展50 kPa围压作用下的循环加卸载试验. 以泊松比、弹性模量提高率及弹塑性变形趋势为参数,分析不同纤维质量分数条件下聚丙烯纤维增强泡沫轻质土的力学特性和变形规律. 研究结果表明:当纤维质量分数达到0.50%~1.00%时,初次弹性模量提高率为56.88%~69.43%,纤维对泡沫轻质土内部初始缺陷的改善作用最佳;纤维增强泡沫轻质土试样的弹性模量提高率随着循环次数的增加呈先增大后减小的趋势,泊松比随着循环次数的增加而增大,在经历最初的2、3次循环荷载作用后趋于稳定直至试样破坏;随着循环次数的增加,纤维增强泡沫轻质土的轴向弹性应变与总应变之比逐渐降低,试样内部损伤变形逐渐累积.


关键词: 纤维增强泡沫轻质土,  循环加卸载,  弹性模量,  损伤变形,  泊松比 
l/mm d/μm ρ/(g·cm?3 tb/℃ tm/℃ a/% E/MPa $ \sigma $/MPa 纤维类型 分散性 抗酸碱性能
12 31 0.91 580 160~180 10-28 ≥3850 ≥500 束状单丝 极好 极高
Tab.1 Tab.1 Basic parameters of polypropylene fiber
序号 mw/mc mw/kg mc/kg mf/kg
01 1∶1.60 221.85 354.96 23.19
02 1∶1.65 217.63 359.09 23.29
03 1∶1.70 213.56 363.05 23.39
04 1∶1.75 209.64 366.88 23.48
05 1∶1.80 205.87 370.56 23.57
06 1∶1.85 202.23 374.12 23.66
07 1∶1.90 198.71 377.55 23.74
Tab.2 Design value of test mix ratio of foam light soil
Fig.1 Change curve of foam light soil flow value with water-cement mass ratio
Fig.2 Change curve of wet weight of foam light soil with water-cement mass ratio
Fig.3 Curve of 7 d unconfined compressive strength of foamed lightweight soil with water-cement mass ratio
Fig.4 GDS unsaturated soil triaxial apparatus
Fig.5 Sample state after test
Fig.6 Comparison diagram of top damage of different fiber mass fraction samples after test
Fig.7 Relation curve of Poisson's ratio and cycle loading and unloading times
序号 n/% En/%
01 0 154.97
02 0.25 107.75
03 0.50 56.88
04 0.75 65.76
05 1.00 69.43
06 1.25 138.38
07 1.50 185.78
Tab.3 Statistical table of increase rate of elastic modulus of foam light soil with different fiber mass fractionsunder initial loading
Fig.8 Relationship curve between elastic modulus and cycle loading and unloading times
Fig.9 Normalized curve of axial elastic strain of foamed lightweight soil with number of cycles under each fiber mass fraction
Fig.10 Normalized radial elastic strain of foamed lightweight soil with different fiber mass fractions as function of number of cycles
Fig.11 Normalized curve of radial plastic strain of foamed lightweight soil with number of cycles under different fiber mass fractions
Fig.12 Normalized curve of axial plastic strain of foamed lightweight soil with number of cycles under different fiber mass fractions
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