本文選題：PFC　切入點(diǎn)：粗糙度效應(yīng)　出處：《吉林大學(xué)》2014年碩士論文

【摘要】：中國(guó)地形地貌復(fù)雜，在工程建設(shè)過(guò)程中，尤其是大型水電、高速公路工程中會(huì)遇到大量的高大邊坡。如何對(duì)這些邊坡進(jìn)行合理設(shè)計(jì)，就成了一個(gè)需要考慮的關(guān)鍵性問(wèn)題。由于巖土體本身的復(fù)雜性，采用常規(guī)的數(shù)學(xué)和物理方法會(huì)耗費(fèi)大量的精力和財(cái)力，在快速發(fā)展的今天，這些方法也慢慢被數(shù)值模擬方法取代。在數(shù)值方法中，一個(gè)最需要考慮，也是最為關(guān)鍵的問(wèn)題就是模型構(gòu)建問(wèn)題。能否構(gòu)建出較為合理的模型，將直接決定設(shè)計(jì)成果是否科學(xué)、可行。高速公路建設(shè)中，山區(qū)的路堤大多使用碎石或者隧道開(kāi)挖棄渣等散粒體材料進(jìn)行填筑。而對(duì)于散粒體材料，使用離散單元法進(jìn)行分析往往更加合適。 本文依托成都理工大學(xué)地質(zhì)災(zāi)害防治與地質(zhì)環(huán)境保護(hù)國(guó)家重點(diǎn)實(shí)驗(yàn)室開(kāi)放基金項(xiàng)目（GZ2009-21）和自然科學(xué)基金項(xiàng)目（41302218），在已有的室內(nèi)大三軸試驗(yàn)數(shù)據(jù)基礎(chǔ)上，使用PFC2D軟件進(jìn)行了顆粒粗糙度效應(yīng)研究。論文詳細(xì)介紹了樣本顆粒形態(tài)及粗糙度的模擬原理和級(jí)配碎石數(shù)值樣本的生成過(guò)程。在此基礎(chǔ)上，以雅瀘高速公路K112+908.16～K113+67段高填路堤橫斷面為基本輪廓，根據(jù)研究需要，對(duì)其進(jìn)行了一定的簡(jiǎn)化，構(gòu)建了不同比例的數(shù)值模型。為了獲取更大的變形值，使變形層次區(qū)分的更加明顯，在不考慮水和地震作用的情況下，本文分析了保持5倍重力作用下，應(yīng)力水平不變時(shí)各數(shù)值模型的應(yīng)力分布和變形情況，經(jīng)對(duì)比分析得出較為合理的模型構(gòu)建方法。本文在研究過(guò)程中，分別采用了Geo-studio中的SIGMA/W模塊和離散元軟件PFC2D為研究工具，分析了原比例模型，1:100模型在應(yīng)力水平相同時(shí)的應(yīng)力分布和變形模式，并分別從橫向和縱向進(jìn)行了對(duì)比分析。同時(shí)，為了探求縮小的倍數(shù)與數(shù)值結(jié)果的關(guān)系，文章應(yīng)用PFC軟件構(gòu)建并分析了1:80和1：60的團(tuán)粒模型。對(duì)于原比例模型，由于實(shí)際應(yīng)用較多，不再做對(duì)比試驗(yàn)。參數(shù)的選取上，使用有限元軟件進(jìn)行邊坡分析時(shí)，輸入的參數(shù)以項(xiàng)目數(shù)據(jù)為基礎(chǔ)，但做了一定的改變。PFC雙軸實(shí)驗(yàn)的數(shù)值模擬時(shí)，仍然采用項(xiàng)目過(guò)程中所做的各種室內(nèi)實(shí)驗(yàn)數(shù)據(jù)，包括顆分、擊實(shí)試驗(yàn)和大三軸實(shí)驗(yàn)等，通過(guò)擬合得到圓粒模型和團(tuán)粒模型的細(xì)觀參數(shù)。使用PFC軟件對(duì)邊坡進(jìn)行分析時(shí)，填石材料采用雙軸試驗(yàn)與室內(nèi)大三軸實(shí)驗(yàn)結(jié)果進(jìn)行擬合得到的數(shù)據(jù)，其他參數(shù)結(jié)合項(xiàng)目報(bào)告，并與有限元分析結(jié)果進(jìn)行擬合得到。主要結(jié)論如下： 1、通過(guò)對(duì)粗粒土的顆粒粗糙度效應(yīng)研究，得出了以下結(jié)論： 團(tuán)粒形態(tài)樣本可以更真實(shí)地模擬碎石材料的骨架-孔隙結(jié)構(gòu)，樣本加載前有著合理、均勻的接觸力分布形式；團(tuán)粒間的鑲嵌結(jié)構(gòu)可以極大的提高樣本強(qiáng)度，變形過(guò)程中體現(xiàn)出不規(guī)則顆粒間的咬合、滑動(dòng)特征；樣本強(qiáng)度與顆粒粗糙度（即D4值）有著線性正比關(guān)系；樣本初始平均接觸數(shù)是決定樣本內(nèi)摩擦角的決定性因素；團(tuán)粒形態(tài)樣本平均接觸數(shù)隨軸向變形發(fā)展的變化規(guī)律再現(xiàn)了顆粒材料彈性變形的微觀力學(xué)機(jī)制。 2、根據(jù)相似理論，本文在第三章分析了邊坡保持應(yīng)力水平不變時(shí)所應(yīng)該遵循的相似準(zhǔn)則，并通過(guò)有限元軟件進(jìn)行了驗(yàn)證。文章同時(shí)得到了不同PFC模型的細(xì)觀參數(shù)之間的關(guān)系。主要結(jié)論為： (1）一般情況下，，邊坡的尺寸與重力加速度乘積為常數(shù)，當(dāng)應(yīng)力水平相同時(shí)，保持其他條件不變，總位移量與模型尺寸的比值為一定值。 (2)對(duì)于PFC邊坡模型，在應(yīng)力水平保持不變的情況下，顆粒平均粒徑與顆粒模量成正比，顆粒法向剛度與切向剛度、法向剛度與顆粒平均半徑成正比，墻體法向和切向剛度成正比。 3、對(duì)于由粗粒土等散粒體材料組成的邊坡，離散單元法具有明顯的優(yōu)越性。 4、不管是采用放大顆粒半徑的原比例模型還是保持粒徑不變的縮小比例模型，其放大或縮小的倍數(shù)主要決定于L/R值、模型生成和加載的時(shí)間，以及模型單元數(shù)。模型單元數(shù)過(guò)少對(duì)運(yùn)算結(jié)果也會(huì)造成明顯影響。本文認(rèn)為在實(shí)際邊坡模型中，即便是縮小比例尺的模型，2000個(gè)圓粒單元對(duì)邊坡的模擬是不夠的。 5、綜合各種分析結(jié)果，一般情況下，團(tuán)粒模型要優(yōu)于圓粒模型。但實(shí)際應(yīng)用中，原比例的團(tuán)粒模型和圓粒模型都可以使用，在使用原比例模型時(shí)，建議用團(tuán)粒模型。 6、1：100比例的團(tuán)粒模型在應(yīng)力、變形兩方面都體現(xiàn)出非常好的優(yōu)越性，與實(shí)際情況吻合的非常好。但是，本文的研究中，1：80和1：60比例的模型x方向的應(yīng)力水平較有限元的結(jié)果偏大，而1：80團(tuán)粒模型的變形情況似乎也有其不合理之處。因此，合理的模型縮小比例尺及計(jì)算結(jié)果的影響因素，還有待進(jìn)一步研究。
[Abstract]:In the process of engineering construction , especially large - scale hydropower and highway engineering , large amount of energy and financial resources are encountered in the engineering construction process , which is a key problem that needs to be considered . In numerical method , these methods are also slowly replaced by numerical simulation methods .

In this paper , we use PFC2D software to study the stress distribution and deformation of the geological disaster prevention and geological environment protection in Chengdu University of Science and Technology ( GZ2009 - 21 ) and Natural Science Foundation ( 41302218 ) .

1 . By studying the effect of particle roughness on coarse grained soil , the following conclusions are drawn :

The morphology of aggregates can simulate the framework - pore structure of crushed stone material , which has a reasonable and uniform distribution of contact force before loading .
the mosaic structure between the granules can greatly improve the strength of the sample , and the meshing and sliding characteristics of irregular particles are reflected in the deformation process ;
The sample intensity is linearly proportional to the particle roughness ( i.e . D4 value ) .
The initial average contact number of samples is the decisive factor to determine the friction angle in the sample ;
The micro - mechanical mechanism of elastic deformation of granular material is reproduced according to the changing law of the average contact number of the aggregate form samples with the development of axial deformation .

2 . According to the similarity theory , the similarity criterion which should be observed when the stress level of the slope is not changed is analyzed in the third chapter , and the relationship between the parameters of different PFC models is obtained .

( 1 ) In general , the dimension of the slope and the product of the gravity acceleration are constant , and when the stress level is the same , other conditions are kept unchanged , and the ratio of the total displacement amount to the model size is a certain value .

( 2 ) For the PFC side slope model , the average particle size of the particles is proportional to the particle ' s modulus under the condition that the stress level is kept constant . The stiffness and tangential stiffness of the particles are directly proportional to the average radius of the particles , and the wall method is proportional to the tangential stiffness .

3 . For slopes composed of bulk materials such as coarse grained soil , the discrete unit method has obvious superiority .

4 . Whether the original scale model with the radius of the enlarged particle or the reduced scale model with the same particle size is adopted , the multiple of the amplification or reduction mainly depends on the L / R value , the time of the generation and loading of the model and the number of the model units .

5 . In general , the aggregate model is better than the round grain model , but in practical application , the original scale model and the round grain model can be used , and when using the original scale model , it is suggested to use the model of aggregates .

In this paper , 1 : 80 and 1 : 60 ratio of the model x - direction stress level is larger than that of the finite element , and the deformation of the 1 : 80 mass model appears to be unreasonable . Therefore , the reasonable model reduces the scale and the influence factors of the calculation results , and it is still to be further studied .

【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TU43

【參考文獻(xiàn)】

相關(guān)博士學(xué)位論文 前1條

1 馬建全;黑方臺(tái)灌區(qū)臺(tái)緣黃土滑坡穩(wěn)定性研究[D];吉林大學(xué);2012年

本文編號(hào)：1725881