【摘要】：隨著國(guó)民經(jīng)濟(jì)的發(fā)展，粉煤灰的排放量和堆積量逐年增加。我國(guó)工業(yè)化、城鎮(zhèn)化的推進(jìn)導(dǎo)致土地資源愈發(fā)緊張，大量工程不得不建立在粉煤灰堆積地區(qū)。而粉煤灰地基屬于軟土地基，其承載力較低，往往不能滿足工程需要，因此必須對(duì)其進(jìn)行處理使其滿足承載力、穩(wěn)定性和抗變形能力的要求。強(qiáng)夯法憑借其施工工藝簡(jiǎn)單、經(jīng)濟(jì)性好、加固效果明顯等優(yōu)點(diǎn)在粉煤灰地基處治中應(yīng)用較多。 然而，與廣泛的工程應(yīng)用相比，強(qiáng)夯的理論研究稍顯滯后。強(qiáng)夯過(guò)程的復(fù)雜性決定了其難以用精確的解析方法求解。其加固機(jī)理和設(shè)計(jì)理論方面尚不成熟，現(xiàn)場(chǎng)施工主要依靠經(jīng)驗(yàn)公式和試驗(yàn)確定，大大限制了強(qiáng)夯法的發(fā)展和應(yīng)用。而傳統(tǒng)的數(shù)值方法均基于小變形假定，工程實(shí)際中夯擊區(qū)將產(chǎn)生較大破壞，其結(jié)果往往不盡如人意。隨著數(shù)值計(jì)算方法的發(fā)展，顯式動(dòng)力非線性有限元理論日趨成熟，為強(qiáng)夯這類非線性大變形問(wèn)題的求解提供了一種新的選擇。在常見(jiàn)土類如濕陷性黃土、碎石土、風(fēng)成砂的強(qiáng)夯研究中，顯式動(dòng)力非線性數(shù)值方法已經(jīng)占有一席之地，取得了一定的成果。相較而言，其在粉煤灰地基中的應(yīng)用目前尚屬空白。 鑒于此，本文首先綜合論述了顯式動(dòng)力非線性有限元數(shù)值理論，并比較了顯式與隱式理論的區(qū)別，然后基于顯式動(dòng)力非線性有限元分析方法，利用ANSYS/LS-DYNA軟件對(duì)強(qiáng)夯問(wèn)題進(jìn)行分析，得出了顯式動(dòng)力非線性數(shù)值模擬方法的一般步驟。結(jié)合某高速公路填土路基強(qiáng)夯實(shí)例建立三維立體模型，對(duì)夯擊碰撞過(guò)程進(jìn)行數(shù)值模擬，，得到了強(qiáng)夯加固范圍及夯后土體的應(yīng)力場(chǎng)、位移場(chǎng)。通過(guò)與現(xiàn)場(chǎng)實(shí)測(cè)數(shù)據(jù)的比對(duì)，驗(yàn)證了顯式動(dòng)力非線性有限元數(shù)值模擬方法在強(qiáng)夯問(wèn)題中的適用性。在此基礎(chǔ)上，研究了岳陽(yáng)地區(qū)強(qiáng)夯處治粉煤灰路基問(wèn)題。通過(guò)對(duì)兩種施工方案分別建模分析，對(duì)夯錘參數(shù)選取問(wèn)題進(jìn)行了探討，分析數(shù)值模擬結(jié)果，比較兩種方案的夯后土體沉降，得出了同能級(jí)下重錘低落距有更好的加固效果的結(jié)論。
[Abstract]:With the development of national economy, the quantity of fly ash discharge and accumulation increases year by year. Due to the development of industrialization and urbanization in China, land resources are becoming more and more tight, and a large number of projects have to be built in fly ash accumulation areas. The fly ash foundation belongs to the soft soil foundation, its bearing capacity is low, often can not meet the engineering needs, so it must be treated to meet the requirements of bearing capacity, stability and deformation resistance. The dynamic compaction method is widely used in the treatment of fly ash foundation with its advantages of simple construction technology, good economy and obvious reinforcement effect. However, compared with the extensive engineering applications, the theoretical research of dynamic compaction is slightly lagging behind. Because of the complexity of dynamic compaction process, it is difficult to solve it with accurate analytical method. The reinforcement mechanism and design theory are not mature, and the field construction mainly depends on the empirical formula and test, which greatly limits the development and application of the dynamic compaction method. However, the traditional numerical methods are based on the assumption of small deformation, and the tamping zone will be destroyed greatly in engineering practice, and the results are often not satisfactory. With the development of numerical methods, explicit nonlinear finite element theory is becoming more and more mature, which provides a new choice for solving nonlinear and large deformation problems such as dynamic compaction. In the dynamic compaction research of common soil such as collapsible loess, gravel soil and wind-formed sand, explicit dynamic nonlinear numerical method has occupied a place, and some achievements have been made. In contrast, its application in fly ash foundation is still blank. In view of this, the explicit dynamic nonlinear finite element numerical theory is firstly discussed, and the difference between explicit and implicit finite element theory is compared, and then based on explicit dynamic nonlinear finite element analysis method, The dynamic compaction problem is analyzed by using ANSYS/LS-DYNA software, and the general steps of explicit nonlinear numerical simulation method are obtained. Based on the example of dynamic compaction of embankment of a certain expressway, a three-dimensional model is established to simulate the impact process of compaction. The range of consolidation and the stress field and displacement field of soil after compaction are obtained. The applicability of explicit nonlinear finite element numerical simulation method in dynamic compaction problem is verified by comparing with field measured data. On this basis, the problem of treating fly ash roadbed with dynamic compaction in Yueyang area is studied. Through modeling and analysis of two construction schemes, the parameter selection of tamping hammer is discussed, the numerical simulation results are analyzed, and the settlement of soil after tamping is compared between the two schemes. It is concluded that the weight drop distance has better reinforcement effect at the same energy level.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：U416.1

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