原状与重塑红黏土强度变化机理
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摘要
为了研究红黏土强度特性及其影响机理,对不同法向应力作用下的原状土样和重塑土样进行了直剪试验。采用扫描电子显微镜测试,对比分析原状土和重塑土颗粒单元间接触、连结状态、孔隙形态及分布等微观结构差异,揭示了土体微观结构对宏观力学性质的影响机理。研究结果表明:当法向应力σ小于临界应力时,原状土的剪应力τ高于重塑土;反之,原状土的τ低于重塑土。临界应力的大小取决于土体孔隙比,孔隙比越大,临界应力越大。原状土黏聚力高于重塑土,内摩擦角低于重塑土。重塑土与原状土力学性质存在明显差异,且差异性的大小取决于原状土微观结构性能的好坏。提出了红黏土闭孔孔隙和开孔孔隙的概念,并将其用于红黏土抗剪强度的机理分析,具有一定的工程指导意义。
In order to study the strength characteristics and influencing mechanism of red clay,direct shear tests were carried out on undisturbed soil samples and remolded soil samples under different normal stresses σ.Scanning electron microscopy( SEM) was used to compare and analyze the differences of microstructure between the undisturbed soil and remolded soil,such as particle unit contact,joint state,pore morphology and distribution. The influence mechanism of soil microstructure on macroscopic mechanical properties was revealed. The results show that when σ is less than the critical stress,the τof the undisturbed soil is higher than that of the remolded soil,otherwise,the undisturbed soil τis lower than the remolded soil.τThe critical value depends on the void ratio of the soil. The larger the void ratio is,the larger the critical value is. The cohesive force of the undisturbed soil is higher than that of the remolded soil,and the internal friction angle is lower than that of the remolded soil. There are significant differences in the mechanical properties between the remodeling soil and the undisturbed soil. The magnitude of the difference depends on the microstructure of the undisturbed soil. The concept of "closed pores and open pores"of red clay is proposed and applied to the mechanism analysis of shear strength of red clay,which has certain engineering guiding significance.
In order to study the strength characteristics and influencing mechanism of red clay,direct shear tests were carried out on undisturbed soil samples and remolded soil samples under different normal stresses σ.Scanning electron microscopy( SEM) was used to compare and analyze the differences of microstructure between the undisturbed soil and remolded soil,such as particle unit contact,joint state,pore morphology and distribution. The influence mechanism of soil microstructure on macroscopic mechanical properties was revealed. The results show that when σ is less than the critical stress,the τof the undisturbed soil is higher than that of the remolded soil,otherwise,the undisturbed soil τis lower than the remolded soil.τThe critical value depends on the void ratio of the soil. The larger the void ratio is,the larger the critical value is. The cohesive force of the undisturbed soil is higher than that of the remolded soil,and the internal friction angle is lower than that of the remolded soil. There are significant differences in the mechanical properties between the remodeling soil and the undisturbed soil. The magnitude of the difference depends on the microstructure of the undisturbed soil. The concept of "closed pores and open pores"of red clay is proposed and applied to the mechanism analysis of shear strength of red clay,which has certain engineering guiding significance.
引文
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[2]张龙起,陈景,曲朝雷.唐山岩溶区桩基施工中几个问题的分析与探讨[J].岩土工程学报,2011,33(S1):325-330.
[3]叶照桂.粤北灰岩地基岩溶发育的特征与对策[J].岩石力学与工程学报,2006,25(S2):3400-3404.
[4]刘之葵,邱晓娟,雷轶.水泥改良桂林红黏土的试验研究[J].公路工程,2016,41(1):7-9.
[5]王麒,陈筠,赵鹏,等.碱污染红黏土物理性质及微观结构试验研究[J].地下空间与工程学报,2017,13(6):1483-1492.
[6]陈学军,檀利波,白汉营,等.柴油污染重塑红黏土直剪力学特性试验研究[J].工程地质学报,2018,26(3):583-591.
[7]赵颖文,孔令伟,郭爱国,等.广西原状红黏土力学性状与水敏性特征[J].岩土力学,2003,24(4):568-572.
[8]史文兵,廖义玲,唐晓玲.贵阳红黏土抗剪强度与含水量关系的探讨[J].路基工程,2011(4):80-81,86.
[9]张添锋,孙德安,刘文捷.桂林压实红黏土抗剪强度与含水率关系[J].上海大学学报(自然科学版),2014,20(5):586-595.
[10]龙万学,陈开圣,肖涛,等.非饱和红黏土三轴试验研究[J].岩土力学,2009,30(S2):28-33.
[11]傅鑫晖,韦昌富,颜荣涛,等.非饱和红黏土的强度特性研究[J].岩土力学,2013,34(S2):204-209.
[12]王中文,洪宝宁,刘鑫,等.红黏土抗剪强度的水敏性研究[J].四川大学学报(工程科学版),2011,43(1):17-22.
[13]毕庆涛,姜国萍,丁树云.含水量对红黏土抗剪强度的影响[J].地球与环境,2005,33(3):144-147.
[14]王洋,汤连生,高全臣,等.水土作用模式对残积红黏土力学性质的影响分析[J].中山大学学报(自然科学版),2007,46(1):128-132.
[15]王继庄.游离氧化铁对红黏土工程特性的影响[J].岩土工程学报,1983,5(1):147-156.
[16]孔令伟,罗鸿禧,袁建新.红黏土有效胶结特征的初步研究[J].岩土工程学报,1995,17(5):42-47.
[17]董肖龙,胡小荣,陈晓宇.正常固结原状饱和黏性土的三剪统一结构性本构模型[J].土木建筑与环境工程,2018,40(3):86-93.
[18]中华人民共和国水利部.土工试验方法标准:GB/T 50123-1999[S].北京:中国计划出版社,1999.
[19]廖义玲,朱立军,周训华.土体中惰性孔隙及其物理力学属性的研究[J].工程勘察,2001(1):5-8.
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