水泥改良粉质粘土的冻土力学特性研究

发布时间：2018-05-18 21:44

  本文选题：水泥土 + 冻土　； 参考：《中国矿业大学》2017年硕士论文

【摘要】：水泥加固与人工冻结是岩土工程常用的两种施工方法,然而随着现实中遇到的越来越复杂的地质条件以及两种施工方法固有的缺点,开始有学者和工程师们提出将两者相结合的新方法,即先对地质条件较差的地层进行注浆加固,然后再进行人工冻结。该新工法源自两种工法但又与其有着明显的不同,而目前对水泥改良土的冻土特性的研究相对较少,本课题即在此背景下提出,通过室内试验和数值模拟两种研究手段,研究上海地区水泥改良粉质粘土的冻土力学特性。课题先进行了水泥改良粉质粘土冻土单轴压缩的室内试验,研究水泥掺量、水灰比、养护龄期、温度等对改良冻土的强度的影响,着重分析了强度、弹性模量等参数与各影响因素之间的关系,得到了对应的拟合关系式。试验结果发现,水泥改良粉质粘土的冻土强度随着水泥掺量的增加、水灰比的减小、养护龄期的延长、温度的降低而增大,同时还发现水泥的加入会使得冻土塑性降低、脆性增加,冻土的应力应变特性和破坏特征亦发生变化。研究还发现,当水泥掺量少于5%时,掺入水泥的效果不大,掺量达到20%,冻土的强度得到很大的提高,脆性明显增强;而当掺量达到40%时,冻土塑性消失,呈现出脆性,该水泥掺量的范围可以为实际工程提供参考。除了室内研究,本文还采用了颗粒流程序PFC2D对水灰比1.0、养护28d、冻结温度为-10℃的水泥土试样的冻土单轴压缩试验进行数值模拟,从细观的角度对试样内部的位移、应力、裂纹发展、试样破坏等进行分析。通过数值模拟的研究,找到了改良冻土的离散元模型,探索了PFC2D在冻土研究中的可行性。数值模拟结果表明,在水泥改良粉质粘土的冻土单轴加载过程中,试样内部的力不是均匀分布的,而是由一条条力链承担,这些力链主要分布在水泥和冰的胶结部分,证明了水泥加入是冻土强度提高的一个原因。利用数值模拟,还对加载过程中内部的裂纹发展、应力分布进行了分析,对冻土单轴压缩过程中的内部变化有了新的认识和理解。通过本课题的研究,可以得知水泥加固和人工冻结的结合是可行的,此外,软件PFC2D也可以在今后的水泥土冻土研究中加以运用,从细观的角度认识和研究冻土。
[Abstract]:Cement reinforcement and artificial freezing are two construction methods commonly used in geotechnical engineering. However, with the increasingly complex geological conditions encountered in reality and the inherent shortcomings of the two construction methods, At first, some scholars and engineers put forward a new method to combine the two, that is to say, to reinforce the strata with poor geological conditions first and then to freeze them artificially. The new method originates from two kinds of engineering methods but is obviously different from them. However, there are relatively few researches on the permafrost characteristics of cement modified soil at present. Under this background, this paper puts forward two kinds of research methods, namely, laboratory test and numerical simulation. The mechanical properties of frozen soil of cement modified silty clay in Shanghai area were studied. In this paper, the laboratory test of uniaxial compression of cement modified silty clay permafrost is carried out, and the influence of cement content, water-cement ratio, curing age and temperature on the strength of improved frozen soil is studied. The relationship between the parameters such as modulus of elasticity and the influencing factors is obtained. The test results show that the strength of frozen soil increases with the increase of cement content, the ratio of water to cement decreases, the curing age prolongs, and the temperature decreases. At the same time, it is found that the addition of cement will reduce the plasticity of frozen soil. With the increase of brittleness, the stress-strain characteristics and failure characteristics of frozen soil also change. It is also found that when the cement content is less than 5, the effect of mixing cement is not very good, the content of cement is 20 and the strength and brittleness of frozen soil are greatly improved, while when the cement content reaches 40, the plasticity of frozen soil disappears and presents brittleness. The range of cement content can provide reference for practical engineering. In addition to the laboratory study, this paper also uses the particle flow program PFC2D to simulate the uniaxial compression test of frozen soil samples with water-cement ratio 1.0, curing 28d and freezing temperature -10 鈩，

本文编号：1907324