【摘要】：西南地區(qū)基礎(chǔ)設(shè)施建設(shè)工程的蓬勃開展形成了眾多的填方工程,所用填料主要由挖方區(qū)爆破而來的碎石和土混合組成,往往具有含石量高(可達60%以上)、巨粒組土粒多(質(zhì)量百分比15%以上)、石塊粒徑大(最大可達1m)的特點,本文稱之為高含石量巨粒土填料。剪切特性作為評價填料工程性質(zhì)最為重要的依據(jù)之一,相關(guān)的抗剪強度指標及剪切變形特征受到工程技術(shù)人員的高度重視。為探究高含石量巨粒土填料的剪切特性,本文依托重慶江北國際機場四期擴建工程,以蒙特卡洛方法為理論基礎(chǔ),利用PFC內(nèi)置的FISH語言進行二次開發(fā),構(gòu)建了基于粒度成分及隨機多邊形石塊的顆粒流填料模型,研究了尺寸效應(yīng)、巨粒組土粒的粒徑及含石量對填料剪切特征的影響,研究成果對山區(qū)丘陵地帶的工程建設(shè)具有重要的參考價值。本文主要的研究內(nèi)容及成果如下:①通過現(xiàn)場槽探、室內(nèi)篩分與數(shù)字圖像處理獲得了高含石量巨粒土填料的粒度成分及表觀特征;石塊形態(tài)分析為構(gòu)建隨機多邊形石塊模型提供了統(tǒng)計依據(jù);對采集的試樣進行室內(nèi)直剪試驗,試驗結(jié)果為后續(xù)顆粒流數(shù)值模擬提供了微觀參數(shù)與宏觀參數(shù)標定的關(guān)鍵資料。②以蒙特卡洛方法為理論基礎(chǔ),構(gòu)建了描述石塊形態(tài)的隨機抽樣模型;利用PFC2D內(nèi)置的FISH語言進行二次開發(fā),構(gòu)建了基于粒度成分及隨機多邊形石塊的顆粒流填料模型,實現(xiàn)了對填料的粒度成分及不規(guī)則多邊形石塊較為準確的模擬。③構(gòu)建直剪試驗顆粒流數(shù)值模型,模擬了填料室內(nèi)直剪試驗的全過程,顆粒流數(shù)值模擬結(jié)果基本反映了填料的剪切特性。通過持續(xù)監(jiān)測并記錄模型中裂隙的位置,獲得了直剪試驗過程中隨著剪切位移的增加剪切面的發(fā)展歷程,并分析了剪切面的形態(tài)特征。④為擴大研究尺度,重新劃分了土石界限粒徑,并相應(yīng)改變模型最小顆粒粒徑,研究了高含石量巨粒土填料的尺寸效應(yīng)。結(jié)果表明,在試樣級配、加載條件均保持不變的情況下,模型尺寸增大,剪應(yīng)力峰值呈減小趨勢,剪應(yīng)力峰值對應(yīng)的剪切應(yīng)變有所減小,剪脹性逐漸減弱,粘聚力及內(nèi)摩擦角亦呈減小趨勢。這種變化在模型尺寸相對較大時趨于平緩。⑤運用等質(zhì)量代換法,保持粗細料的含量不變,設(shè)計了不同巨粒組土粒分布的數(shù)值模型。數(shù)值模擬結(jié)果表明:隨著模型中粒徑較大的石塊逐漸被粒徑小、數(shù)量多的石塊所取代,粘聚力逐漸降低,但內(nèi)摩擦角呈增大趨勢。以此指導(dǎo)工程實踐,填筑施工中應(yīng)按照相關(guān)規(guī)范控制石塊的粒徑,對于粒徑超出規(guī)范規(guī)定的石塊應(yīng)對其進行分解。⑥保持加載條件及各石塊粒組的相對比例不變,設(shè)計了含石量分別為10%、30%、40%、50%、60%、70%、80%、90%的數(shù)值模型。數(shù)值模擬結(jié)果表明:含石量越高,則剪應(yīng)力峰值越大,模型表現(xiàn)出更大的剛度,剪應(yīng)力-剪切應(yīng)變曲線近彈性段的斜率越大,剪應(yīng)力峰值對應(yīng)的剪切應(yīng)變越小,剪脹性逐漸增強。粘聚力及內(nèi)摩擦角隨不同含石量的變化曲線可分為三個部分:1)含石量10%~40%時,隨著含石量增大,內(nèi)摩擦角逐漸增大,粘聚力逐漸降低;2)含石量40%~70%時,隨著含石量增大,粘聚力增加到一定程度后逐漸穩(wěn)定,內(nèi)摩擦角變化較小;3)含石量70%~90%時,粘聚力隨含石量的增大顯著降低,而內(nèi)摩擦角明顯增大。根據(jù)以上結(jié)論,含石量大于70%時,隨著含石量的增大,填料的粘聚力大幅降低,加之夯實質(zhì)量難以得到保證,因此在填方工程中應(yīng)避免使用含石量大于70%的填料。
[Abstract]:The foundation of the infrastructure construction project in the southwest part of the Southwest has formed a large number of filling projects. The filler used mainly consists of crushed stone and soil mixed by blasting in the excavation area, and often has high stone content (up to 60%), and the large-grain group of soil particles (with a mass percentage of more than 15%). The size of the stone is large (up to 1m), which is referred to as the high-stone-containing large-particle soil filler. The shear characteristic is one of the most important bases for evaluating the properties of the filler, and the related shear strength and shear deformation characteristics are highly valued by the engineering and technical personnel. In order to study the shear characteristics of the high-stone-containing giant soil filler, this paper, based on the four-period expansion project of the Chongqing Jiangbei International Airport, based on the Monte-Carlo method, uses the FISH language built-in of the PFC to carry out secondary development. The particle flow packing model based on the particle size component and the random polygonal block is constructed, and the effect of the size effect, the particle size of the giant particle and the stone content on the shear characteristics of the filler is studied. The research results are of great reference value to the construction of the hilly land in the mountainous area. The main contents and results of this paper are as follows: The particle size composition and apparent characteristic of the high-stone-containing giant-particle soil filler are obtained through the on-site investigation, in-room screening and digital image processing, and the analysis of the stone shape provides a statistical basis for the construction of the random polygonal block model. An indoor direct shear test is carried out on the collected samples, and the experimental results provide the key data of the micro-parameter and macro-parameter calibration for subsequent particle flow numerical simulation. Based on the Monte-Carlo method, a random sampling model for describing the shape of the stone is constructed, and the particle flow packing model based on the particle size component and the random polygonal block is constructed by the secondary development of the FISH language built in the PFC2D. and the accurate simulation of the particle size component and the irregular polygonal block of the filler is realized. The numerical model of the particle flow of the direct shear test is constructed, and the whole process of the direct shear test in the packing chamber is simulated, and the numerical simulation results of the particle flow basically reflect the shearing characteristics of the filler. By continuously monitoring and recording the position of the fracture in the model, the development of the shear plane with the shear displacement in the course of the direct shear test is obtained, and the morphological characteristics of the shear plane are also analyzed. In order to enlarge the research scale, the particle size of the soil-rock boundary is re-divided, and the minimum particle size of the model is changed accordingly, and the size effect of the high-stone-containing giant-particle soil filler is studied. The results show that, under the condition that the sample stage and the loading condition are all the same, the size of the model is increased, the peak value of the shear stress is reduced, the shear strain corresponding to the peak value of the shear stress is reduced, the shear expansion is gradually reduced, and the viscosity and the internal friction angle are also reduced. this change tends to be gentle as the size of the model is relatively large. The numerical model of soil particle distribution in different macro-particle groups was designed by using the mass substitution method and other mass substitution method to keep the content of the coarse and fine material unchanged. The results of the numerical simulation show that, with the larger diameter of the stone in the model, the particle size is small, the number of stones is replaced, and the cohesive force is gradually reduced, but the internal friction angle is increasing. In order to guide the practice of the project, the particle size of the stone shall be controlled in accordance with the relevant specifications in the filling construction, and the stone shall be decomposed for the stone with the particle size exceeding the specification. In order to maintain the loading condition and the relative proportion of each block group, the numerical model with the stone content of 10%, 30%, 40%, 50%, 60%, 70%, 80% and 90%, respectively, was designed. The results of the numerical simulation show that the higher the stone content, the higher the shear stress peak, the higher the shear stress-shear strain curve near the elastic section, the smaller the shear strain corresponding to the shear stress peak, and the shear expansion. the viscosity and the internal friction angle can be divided into three parts along with the change curve of the different rock-containing quantity: 1) when the stone-containing amount is 10-40%, the internal friction angle is gradually increased with the increase of the stone-containing amount, and the viscous-accumulation force is gradually reduced; and 2) when the stone-containing amount is 40-70%, the stone-containing amount is increased, When the cohesive force is increased to a certain extent, the internal friction angle is small; 3) When the stone content is 70-90%, the adhesion force is significantly reduced with the increase of the stone content, and the internal friction angle is obviously increased. According to the above conclusion, when the stone content is more than 70%, with the increase of the stone content, the adhesion and accumulation force of the filler is greatly reduced, and the compaction quality is difficult to be guaranteed, so that the filler with the stone content of more than 70% shall be avoided in the filling project.
【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU751.4;TU432

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