本文選題：水泥土 + 凍土��； 參考：《中國礦業(yè)大學》2017年碩士論文

【摘要】：水泥加固與人工凍結(jié)是巖土工程常用的兩種施工方法,然而隨著現(xiàn)實中遇到的越來越復雜的地質(zhì)條件以及兩種施工方法固有的缺點,開始有學者和工程師們提出將兩者相結(jié)合的新方法,即先對地質(zhì)條件較差的地層進行注漿加固,然后再進行人工凍結(jié)。該新工法源自兩種工法但又與其有著明顯的不同,而目前對水泥改良土的凍土特性的研究相對較少,本課題即在此背景下提出,通過室內(nèi)試驗和數(shù)值模擬兩種研究手段,研究上海地區(qū)水泥改良粉質(zhì)粘土的凍土力學特性。課題先進行了水泥改良粉質(zhì)粘土凍土單軸壓縮的室內(nèi)試驗,研究水泥摻量、水灰比、養(yǎng)護齡期、溫度等對改良凍土的強度的影響,著重分析了強度、彈性模量等參數(shù)與各影響因素之間的關(guān)系,得到了對應(yīng)的擬合關(guān)系式。試驗結(jié)果發(fā)現(xiàn),水泥改良粉質(zhì)粘土的凍土強度隨著水泥摻量的增加、水灰比的減小、養(yǎng)護齡期的延長、溫度的降低而增大,同時還發(fā)現(xiàn)水泥的加入會使得凍土塑性降低、脆性增加,凍土的應(yīng)力應(yīng)變特性和破壞特征亦發(fā)生變化。研究還發(fā)現(xiàn),當水泥摻量少于5%時,摻入水泥的效果不大,摻量達到20%,凍土的強度得到很大的提高,脆性明顯增強;而當摻量達到40%時,凍土塑性消失,呈現(xiàn)出脆性,該水泥摻量的范圍可以為實際工程提供參考。除了室內(nèi)研究,本文還采用了顆粒流程序PFC2D對水灰比1.0、養(yǎng)護28d、凍結(jié)溫度為-10℃的水泥土試樣的凍土單軸壓縮試驗進行數(shù)值模擬,從細觀的角度對試樣內(nèi)部的位移、應(yīng)力、裂紋發(fā)展、試樣破壞等進行分析。通過數(shù)值模擬的研究,找到了改良凍土的離散元模型,探索了PFC2D在凍土研究中的可行性。數(shù)值模擬結(jié)果表明,在水泥改良粉質(zhì)粘土的凍土單軸加載過程中,試樣內(nèi)部的力不是均勻分布的,而是由一條條力鏈承擔,這些力鏈主要分布在水泥和冰的膠結(jié)部分,證明了水泥加入是凍土強度提高的一個原因。利用數(shù)值模擬,還對加載過程中內(nèi)部的裂紋發(fā)展、應(yīng)力分布進行了分析,對凍土單軸壓縮過程中的內(nèi)部變化有了新的認識和理解。通過本課題的研究,可以得知水泥加固和人工凍結(jié)的結(jié)合是可行的,此外,軟件PFC2D也可以在今后的水泥土凍土研究中加以運用,從細觀的角度認識和研究凍土。
[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，

本文編號：1907324