干湿循环对云南饱和重塑红土固结不排水剪切特性的影响
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摘要
以云南红土为研究对象,以反复的低温脱湿、浸泡增湿为干湿循环控制条件,考虑干湿循环次数、干密度和围压等影响因素,利用TSZ-2型全自动三轴仪,开展干湿循环作用下饱和重塑红土的固结不排水剪切试验,研究不同影响因素对干湿循环饱和重塑红土三轴剪切特性的影响。试验结果表明:固结不排水条件下,饱和重塑红土的应力-应变关系表现出应变软化的特征,孔压曲线呈S形变化。随着干湿循环次数的增多,饱和重塑红土的峰值应力、峰值应变、峰值孔压均出现减小,固结排水量、残余应力变化量、残余应变变化量均出现增大;随着干密度的增大,峰值应力、残余应力增大,饱和重塑红土的固结排水量、峰值应变、残余应变、峰值孔压减小;随围压的增大,饱和重塑红土的固结排水量、峰值应力、峰值应变、残余应力、残余应变、峰值孔压均出现增大。饱和重塑红土的总应力强度指标和有效应力强度指标随干湿循环次数的增多呈波动减小的变化趋势。反复的干湿循环对饱和重塑红土的微结构产生了损伤,影响了固结过程中的排水情况和试样的密实状态,相应地改变了剪切过程中的受力特性。
The influence of different factors on the shear characteristics of saturated remolded laterite after being subjected wetting-drying cycle was studied. Consolidated-undrained( CU) test,on Yunnan laterite after wettingdrying cycle was performed with TSZ-2 full automatic triaxial test apparatus. Repeated low-temperature dehumidification and soaking humidification were the control conditions. Frequencies of wetting-drying cycle,dry densities and confined pressures were taken as influence factors.The results showed that the stress-strain relationship of saturated remolded laterite under CU condition presented the characteristics of strain softening,and the pore water pressure curve changed in S-shaped. With the increase of wetting-drying cycles,the peak stress,peak strain and peak pore water pressure of saturated remolded laterite decreased,the consolidation drainage volume,residual stress and residual strain increased; with the increase of dry density,the peak stress and residual stress increased,the consolidation drainage volume,peak strain,residual strain and peak pore water pressure of specimens decreased;with the increase of confined pressure,the peak stress,peak strain,residual stress,residual strain and peak pore water pressure of specimens increased. The total stress and effective stress strength indexes of saturated remolded laterite presented a decrease tendency with the increase of wetting-drying cycles. Wetting-drying cycling damaged the microstructure of laterite,thus affecting the drainage and compactness of laterite,and correspondingly changed the mechanical properties.
The influence of different factors on the shear characteristics of saturated remolded laterite after being subjected wetting-drying cycle was studied. Consolidated-undrained( CU) test,on Yunnan laterite after wettingdrying cycle was performed with TSZ-2 full automatic triaxial test apparatus. Repeated low-temperature dehumidification and soaking humidification were the control conditions. Frequencies of wetting-drying cycle,dry densities and confined pressures were taken as influence factors.The results showed that the stress-strain relationship of saturated remolded laterite under CU condition presented the characteristics of strain softening,and the pore water pressure curve changed in S-shaped. With the increase of wetting-drying cycles,the peak stress,peak strain and peak pore water pressure of saturated remolded laterite decreased,the consolidation drainage volume,residual stress and residual strain increased; with the increase of dry density,the peak stress and residual stress increased,the consolidation drainage volume,peak strain,residual strain and peak pore water pressure of specimens decreased;with the increase of confined pressure,the peak stress,peak strain,residual stress,residual strain and peak pore water pressure of specimens increased. The total stress and effective stress strength indexes of saturated remolded laterite presented a decrease tendency with the increase of wetting-drying cycles. Wetting-drying cycling damaged the microstructure of laterite,thus affecting the drainage and compactness of laterite,and correspondingly changed the mechanical properties.
引文
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[3]何金龙,黄英,王琳,等.库水作用下库岸边坡红土的侵蚀模型试验研究[J].工程勘察,2015,43(9):1-7.
[4]朱建群,冯浩,龚琰,等.基于干湿循环作用的红黏土强度特征分析[J].常州工学院学报,2017,30(3):1-5.
[5]龚琰.干湿循环作用下红黏土的变形和强度特性研究[D].长沙:湖南科技大学,2015.
[6]陈开圣.干湿循环作用下红黏土抗剪强度特性研究[J].公路,2016,61(2):45-49.
[7]朱宝柱,刘盼,李文,等.干湿循环作用下长沙高速粉质黏土软化特性试验研究[J].湖南交通科技,2017,43(1):1-5,83.
[8]赵雄飞.荷载与干湿循环作用下红黏土变形特性研究[D].贵阳:贵州大学,2016.
[9]穆坤,孔令伟,张先伟,等.红黏土工程性状的干湿循环效应试验研究[J].岩土力学,2016,37(8):2247-2253.
[10]袁志辉.干湿循环下黄土的强度及微结构变化机理研究[D].西安:长安大学,2015.
[11]邓欣.干湿循环条件下云南红土的强度变形特性研究[D].昆明:昆明理工大学,2013.
[12]何金龙.库水作用下云南库岸红土干湿循环特性研究[D].昆明:昆明理工大学,2015.
[13]周志伟,黄英,程富阳,等.干湿循环下云南红土型坝坡模型试验研究[J].勘察科学技术,2017(5):1-7.
[14]中华人民共和国水利部.土工试验规程:SL 237-1999[S].北京:中国水利水电出版社,1999.
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