本文選題：地震液化　切入點(diǎn)：含粘粒砂土　出處：《浙江大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：地震液化會(huì)導(dǎo)致巨大的財(cái)產(chǎn)損失和人員傷亡,液化評(píng)價(jià)的相關(guān)研究具有重要的科學(xué)意義和工程價(jià)值。目前,基于純凈砂和含粉粒砂土的液化相關(guān)研究已經(jīng)比較完善,而針對(duì)較高粘粒含量砂土液化行為的研究則比較匱乏,對(duì)于其液化規(guī)律和內(nèi)在實(shí)質(zhì)認(rèn)識(shí)不足。人們?cè)缙谡J(rèn)為僅純凈砂土?xí)l(fā)生地震液化,而具有塑性的較高粘粒含量砂土 /粉土則不發(fā)生地震液化。近些年全球范圍的多場(chǎng)重大地震中,都出現(xiàn)了細(xì)粒土的液化實(shí)例,這引起了相關(guān)學(xué)者對(duì)高粘粒含量砂性土液化問題的關(guān)注。大量的含粉粒土體液化研究和少量的含粘粒土體液化研究表明,含細(xì)粒土體的特性隨著細(xì)粒含量的變化呈現(xiàn)出不同的特點(diǎn)。低細(xì)粒含量時(shí)土體表現(xiàn)為類似純凈砂土的動(dòng)力特性;隨細(xì)粒含量增加,土體逐漸表現(xiàn)出粘性土特性;而在接近“類砂土”到“類粘土”轉(zhuǎn)換臨界細(xì)粒含量(TFC)時(shí),土體同時(shí)具備砂性土和粘性土的土體特性,這一細(xì)粒含量區(qū)間也被稱為“過渡帶”。本文主要針對(duì)高粘粒含量砂土,開展一系列室內(nèi)試驗(yàn)并結(jié)合課題組已有研究成果分析粘粒對(duì)于土體液化特性的影響。希望通過大量的室內(nèi)動(dòng)三軸試驗(yàn)和合理的對(duì)照分析,深入理解粘粒對(duì)土體液化特性的影響規(guī)律,揭示含粘粒砂土地震液化機(jī)制,通過建立能夠適用于不同粘粒含量的含粘粒砂土CRR-Vs1表征模型,為實(shí)際工程場(chǎng)地中含粘粒砂土的液化評(píng)價(jià)提供科學(xué)依據(jù)。主要的研究?jī)?nèi)容包括:1.提出利用超固結(jié)比OCR控制低塑性砂性土結(jié)構(gòu)性的試驗(yàn)方法:“點(diǎn)對(duì)點(diǎn)”的液化判別方法是通過室內(nèi)試驗(yàn)結(jié)果反應(yīng)原位土體特性的典型方法,合理設(shè)計(jì)試驗(yàn)的關(guān)鍵在于采用有效的方法使得室內(nèi)土體試樣的結(jié)構(gòu)性恢復(fù)至原位水平,并同時(shí)保證試樣的孔隙比及應(yīng)力狀態(tài)與原位土體保持一致。已有研究提出了一種預(yù)振的方法僅能夠有效地恢復(fù)純凈砂土試樣的結(jié)構(gòu)性,而本文所提出的超固結(jié)方法,則可以有效恢復(fù)較高粘粒含量且具備一定塑性土體試樣的結(jié)構(gòu)性。基于土體試樣的應(yīng)力路徑、Hardin公式和線彈性理論推導(dǎo),驗(yàn)證超固結(jié)方法的合理性并給出設(shè)計(jì)超固結(jié)比的計(jì)算方法。2.粘粒含量(CC)對(duì)砂性土剛度特征的影響規(guī)律:針對(duì)高粘粒含量(CC30、CC40)砂土開展測(cè)試剪切波速的分級(jí)固結(jié)試驗(yàn),分析試驗(yàn)數(shù)據(jù)得到CC30、CC40含粘粒砂土的Hardin曲線擬合結(jié)果,與已有的低粘粒含量砂土(CCO、CC10、CC15、CC20) Hardin曲線整合分析,擬合Hardin公式中參數(shù)(A,n)與粘粒含量(CC)之間的關(guān)系。發(fā)現(xiàn)以CC20為界限,Hardin公式中參數(shù)(A,n)在較低和較高兩段粘粒含量(CC)范圍內(nèi)差異較大且隨CC呈現(xiàn)不同的變化趨勢(shì)�？紤]本文所用含粘粒砂土(蕭山粘土福建細(xì)砂)的“類粘土”、“類砂土”轉(zhuǎn)換臨界粘粒含量(TFC)是20%左右,因而認(rèn)為類砂和類粘土的剛度特征差異較大且受粘粒含量影響變化規(guī)律不同,應(yīng)分開考慮。試驗(yàn)過程選擇同時(shí)考慮砂顆粒和粘土顆粒對(duì)土骨架貢獻(xiàn)的等效骨架孔隙比作為本次試驗(yàn)的對(duì)照標(biāo)準(zhǔn)。3.粘粒含量對(duì)砂性土動(dòng)強(qiáng)度的影響規(guī)律:針對(duì)CC30含粘粒砂土開展系統(tǒng)的動(dòng)三軸液化試驗(yàn),補(bǔ)充特定密實(shí)度CC10和CC20的動(dòng)強(qiáng)度試驗(yàn),并結(jié)合已有的低粘粒含量砂土(CCO、CC10、CC20)動(dòng)三軸液化試驗(yàn)結(jié)果,分析特定等效骨架孔隙比(e*)、不同CC含粘粒砂土的動(dòng)強(qiáng)度曲線,總結(jié)粘粒含量對(duì)于土體試樣動(dòng)強(qiáng)度曲線的影響規(guī)律。發(fā)現(xiàn)不同密實(shí)狀態(tài)(e*=1.0105,e*=0.7977,e*=0.6873)含粘粒砂土的動(dòng)強(qiáng)度隨粘粒含量變化規(guī)律不同,結(jié)合不同密實(shí)度砂土受動(dòng)荷載作用下的體變特性,分三種情況總結(jié)粘粒含量對(duì)于含粘粒砂土動(dòng)強(qiáng)度的影響規(guī)律。4.建立含粘粒砂土的動(dòng)強(qiáng)度剪切波速表征模型:基于不同密實(shí)度試樣動(dòng)三軸液化試驗(yàn)結(jié)果建立CC30含粘粒砂土的CRR-Vs1表征模型。根據(jù)前文的分析結(jié)果,將CRR-Vs1表征模型中重要參數(shù)(kN, emin, n,)以粘粒含量(CC)替代后得到能夠適用于不同粘粒含量含粘粒砂土液化評(píng)價(jià)的CRR-Vs1表征模型�；谶@一表征模型和原位土體的相關(guān)信息(剪切波速、飽和密度以及粘粒含量)可直接得到原位土體的抗液化強(qiáng)度,用于指導(dǎo)實(shí)際工程中的場(chǎng)地液化評(píng)價(jià)問題。5.細(xì)粒土液化判別工程實(shí)例:某工程地震災(zāi)害評(píng)價(jià)專題中粘質(zhì)粉土依據(jù)土性指標(biāo)被判定為“類粘-類砂土”,即土體特性既具有粘土特性,同時(shí)也具備砂土的部分特性。已有的規(guī)范方法在針對(duì)該層土體進(jìn)行液化判別的過程中得到了偏不安全的判別結(jié)果。本文采用三種液化詳判的方法對(duì)該層粘質(zhì)粉土進(jìn)行液化評(píng)價(jià):1)通過室內(nèi)“點(diǎn)對(duì)點(diǎn)”液化判別試驗(yàn)確定了該層粘質(zhì)粉土在實(shí)際設(shè)防烈度下的液化可能性;2)分別依據(jù)室內(nèi)試驗(yàn)結(jié)果和前面提出的含粘粒砂土 CRR-Vs1表征模型建立該層粘質(zhì)粉土的CRR-Vs1表征模型并對(duì)其進(jìn)行液化分析,得到了與方法1 一致的判別結(jié)果;3)基于原位標(biāo)準(zhǔn)貫入試驗(yàn)測(cè)試結(jié)果對(duì)該層粘質(zhì)粉土進(jìn)行液化分析確定其在罕遇地震情況的液化可能。對(duì)照液化詳判結(jié)果驗(yàn)證了CRR-Vs1表征模型在細(xì)粒土液化分析方面的適用性。
[Abstract]:Seismic liquefaction will lead to great loss of property and casualties, the related research of liquefaction evaluation has important scientific significance and engineering value. At present, the related research of pure sand liquefaction and powder sand has been more perfect based on the behavior of sand liquefaction high clay content is relatively scarce, for its lack of regularity and liquefaction the intrinsic essence understanding. People think that only happens early pure sand seismic liquefaction, and has a high content of clay sand / plastic silt is not the earthquake liquefaction. A number of major earthquakes in recent years in the world, there are examples of fine grained soil liquefaction, which caused the scholars attention to the high clay content of sand soil liquefaction problem. A large amount of silt liquefaction research and a small amount of clay soil liquefaction research shows that the characteristics of soil containing fine change with fine content is Show different characteristics. When the content of soil is low fine dynamic characteristics similar to pure sand; with fine content increased, the soil gradually showed the properties of clay; and when approaching the "sand" to "clay" conversion critical fine content (TFC), and soil soil characteristics of sandy soil and preparation clay, the zone of fine content is also known as the "transition zone". This article mainly aims at the sand high clay content, carry out a series of laboratory tests and based on the existing research results of clay soil liquefaction characteristics for dynamic analysis of three axis control. To test and reasonable through a large number of indoor, deep to understand the effect of clay on liquefaction characteristics of soil containing clay, reveal the sand liquefaction mechanism, the CRR-Vs1 model containing clay sand characterization can be applied to different clay content, for the actual project site To provide a scientific basis for evaluation of liquefaction of sand with clay. The main research contents include: 1. the overconsolidation ratio OCR control test method of low plastic sand soil structural: "liquefaction methods point" is the typical method through the laboratory test results of in situ soil characteristics, using effective methods to make the indoor soil sample structure restored to the in-situ experimental design is the key to a reasonable level, and at the same time to ensure void ratio and stress state of specimen and in situ soil is consistent. The research puts forward a method of pre vibration only can effectively restore the pure sand sample structure, over consolidation method proposed by this paper, you can the effective recovery of high clay content and have a certain plastic soil sample. The structural stress path of soil sample based on Hardin formula and linear elastic theory is verified The consolidation method is reasonable and the calculation method is proposed to design the overconsolidation ratio.2. clay content (CC) influence on sand soil stiffness characteristics for high clay content (CC30, CC40) classification of sand consolidation tests carried out to test the shear wave velocity analysis, the test data of CC30, Hardin curve fitting results of CC40 containing clay sand low clay content of sand, and the (CCO, CC10, CC15, CC20) Hardin curve analysis integration, parameter fitting formula Hardin (A, n) and clay content (CC). The relationship between the CC20 from the limits of parameter Hardin in the formula (A, n) in the low and high two the clay content (CC) in the range of differences and different trends of change with CC. This paper considers the clay containing sand (Xiaoshan Fujian clay fine sand) "clay", "sand" conversion critical clay content (TFC) is about 20%, so that the sand and clay of the first class Characteristics of the differences and changes of different clay content, should be considered separately. The test process selection considering equivalent skeleton pore sand particles and clay particles on the soil skeleton contribution ratio as control standard.3. clay content in the test of dynamic strength of sand soil was investigated. In three triaxial liquefaction test CC30 with the clay sand to carry out the system, the dynamic strength test of certain density CC10 and CC20, and combined with the low content of clay sand existing (CCO, CC10, CC20) three triaxial liquefaction test results, analysis of the specific equivalent skeleton void ratio (e*), different CC containing clay sand dynamic strength curve, summarize the content of clay the influence of soil sample dynamic strength curve. Different density (e*=1.0105, e*=0.7977, e*=0.6873) of the dynamic strength of clay containing sand changes with different clay content, combined with different density sands by The dynamic characteristics of variable loads, three kinds of dynamic strength of shear wave velocity characterization model summary of clay content for.4. effect of clay sand containing dynamic strength is set up with the clay sand samples with different densities: dynamic results of three liquefaction test to establish CRR-Vs1 representation model based on soil CC30 containing clay sand. According to the above analysis results the CRR-Vs1 representation model of important parameters (kN, Emin, n) with clay content (CC) can be obtained after alternative characterization of CRR-Vs1 model in different clay content evaluation of sand liquefaction clay. Information on this characterization model and in situ soil (based on shear wave velocity, saturation density and clay content) can be directly obtained in situ soil liquefaction strength, used to guide the evaluation of site liquefaction in actual engineering project.5. discriminant of fine grained soil liquefaction: a project of earthquake disaster assessment project price s. On the basis of silt soil index was determined as "viscous type sand", which has the characteristic of clay soil properties, but also have some characteristics of sand. The existing methods for the specification in the process of soil liquefaction are unsafe identification results. Liquefaction evaluation of the clay layer silt using three methods of liquefaction judgement mining in this paper: 1) through the indoor "point to point" liquefaction test to determine the liquefaction potential of the clayey silt layer in the fortification intensity; 2) CRR-Vs1 model establishment of the clayey silt clay sand layer containing CRR-Vs1 representation model respectively according to the indoor test results and proposed and liquefaction analysis on it, and got the consistent results of 1 methods; 3) in-situ standard penetration test results based on the layer of clay silt liquefaction analysis to determine the rare earthquake. The liquefaction possibility of the condition. The results of the comparison of the liquefaction test verify the applicability of the CRR-Vs1 characterization model in the analysis of the liquefaction of fine grained soil.

【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU435

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