【摘要】：近年來全球范圍內(nèi)長持時強震頻發(fā),長持時強震液化后產(chǎn)生過大沉降變形異常嚴重,是導致強震區(qū)地下基礎設施及生命線系統(tǒng)失效破壞的主要原因之一。本文針對長持時強震作用下場地液化后沉降機制問題,開展單元體固結(jié)試驗、動三軸振動試驗(包括液化工況和非液化工況)研究,了解砂土受振動荷載后的變形特性,并進一步提出了基于固結(jié)和循環(huán)應力歷史的再固結(jié)排水模型和沉降簡化計算方法。同時,開展了兩個離心機模型試驗(正弦波模型和地震波模型)模擬長持時強震后的液化沉降,對上述模型和計算方法加以驗證。本文還針對液化場地的邊值問題提出相應的累積剪應變比的計算方法,并做了現(xiàn)場實例沉降計算。具體內(nèi)容包括： (1)動三軸振動(包括液化工況和非液化工況)研究中采用累積剪應變比作為砂土結(jié)構(gòu)性損傷的表征指標,確定了單元體試樣中臨界累積剪應變作為液化判別的標準； (2)飽和砂土在振動非液化工況下排水體變僅由再固結(jié)機制控制,其再固結(jié)過程的規(guī)律與固結(jié)試驗中的回彈段的規(guī)律相似,其再固結(jié)指數(shù)在e-logp曲線中的斜率隨著有效應力的增大而增大,且再固結(jié)指數(shù)與相同條件下的回彈指數(shù)相當； (3)飽和砂土液化后體變由再沉積和再固結(jié)兩種機制組成：其中再沉積部分與所受振動歷史密切相關,土骨架累積剪應變比越大、再沉積體變越大；而再固結(jié)部分受先期固結(jié)歷史影響顯著,再固結(jié)曲線會沿原有正常固結(jié)曲線趨勢發(fā)展,其穩(wěn)定段再固結(jié)指數(shù)與相同條件下的壓縮指數(shù)稍大,前者大約為后者的1.3-1.5倍之間,于是,壓縮指數(shù)可以用于再固結(jié)指數(shù)的估算； (4)提出了考慮先期固結(jié)和振動歷史的砂土再固結(jié)模型和簡化算法,將再沉積和再固結(jié)兩者統(tǒng)一表達成再固結(jié)體變,該簡化后體變的規(guī)律可用累積剪應變比(γacm/γacm0)與假設起始應力比(σ1a：/σ1v0)的相關關系加以描述,并建議了再固結(jié)指數(shù)和假設初始應力的確定方法； (5)開展了系列水平場地地震液化離心機模型試驗,監(jiān)測模型固結(jié)和振動液化過程急排水過程的沉降,從模型尺度進一步揭示砂土在長持時強震作用下的液化工況下的體變規(guī)律,并初步驗證了本文模型與簡化算法在計算非液化工況和液化工況下沉降的有效性。 (6)根據(jù)模型場地累積剪應變數(shù)據(jù)給出了模型或現(xiàn)場等邊值問題下的臨界累積剪應變判別液化標準,提出了依據(jù)現(xiàn)場地表加速度記錄計算地表下各土層的累積剪應變的方法,并針對東日本地震中Urayasu地區(qū)某液化場地的液化進行沉降計算。
[Abstract]:In recent years, the long-lasting strong earthquakes occur frequently in the world, and the excessive settlement and deformation caused by the liquefaction of long-lasting strong earthquakes are very serious, which is one of the main reasons leading to the failure of underground infrastructure and lifeline system in strong earthquake areas. Aiming at the settlement mechanism of site liquefaction under the action of long-lasting strong earthquake, the consolidation test and dynamic triaxial vibration test (including liquefaction condition and non-liquefaction condition) are carried out to understand the deformation characteristics of sand under vibration load. Furthermore, a reconsolidation drainage model based on consolidation and cyclic stress history and a simplified settlement calculation method are proposed. At the same time, two centrifuge model tests (sinusoidal wave model and seismic wave model) were carried out to simulate the liquefaction settlement after long duration strong earthquake. In this paper, the corresponding calculation method of cumulative shear strain ratio is proposed for the boundary value problem of liquefaction site, and the settlement calculation of site example is made. The main contents are as follows: (1) in the study of dynamic triaxial vibration (including liquefaction and non-liquefaction), the cumulative shear strain ratio is used as the index to characterize the structural damage of sand. The critical cumulative shear strain in the unit sample is determined as the criterion of liquefaction. (2) the deformation of saturated sand is controlled only by the mechanism of reconsolidation under the condition of vibration and non-liquefaction. The law of the reconsolidation process is similar to that of the springback section in the consolidation test. The slope of the reconsolidation index in the e-logp curve increases with the increase of the effective stress, and the re-consolidation index is similar to the springback index under the same conditions. (3) the liquefaction of saturated sand consists of two mechanisms: redeposition and reconsolidation. The redepositional part is closely related to the vibration history, and the larger the cumulative shear strain ratio of soil skeleton is, the larger the redepositional body is; However, the reconsolidation part is significantly affected by the preconsolidation history, and the reconsolidation curve will develop along the trend of the original normal consolidation curve. The reconsolidation index of the stable section is slightly larger than that of the compression index under the same conditions, and the former is about 1.3-1.5 times of the latter, so, Compression exponent can be used to estimate the reconsolidation index. (4) A sand soil reconsolidation model and a simplified algorithm considering the pre-consolidation and vibration history are proposed. The simplified law of body deformation can be described by the correlation between the cumulative shear strain ratio (緯 acm/ 緯 acm0) and the assumed initial stress ratio (蟽 1a:/ 蟽 1v0), and the method of determining the reconsolidation index and the hypothetical initial stress is suggested. (5) A series of horizontal site seismic liquefaction centrifuge model tests were carried out to monitor the settlement of the model during consolidation and vibration liquefaction. Based on the model scale, the body deformation law of sand under the condition of liquefaction under the action of long-lasting strong earthquake is further revealed. The validity of the proposed model and the simplified algorithm in the calculation of settlement under non-liquefaction and liquefaction conditions are preliminarily verified. (6) based on the cumulative shear strain data of the model site, the impending problem of model or field isobaric value is given. Boundary cumulative shear strain criterion for liquefaction, A method for calculating the accumulated shear strain of each soil layer under the ground surface based on the field acceleration records is proposed and the settlement of a liquefaction site in Urayasu area during the East Japan earthquake is calculated.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TU441

【參考文獻】

相關期刊論文 前10條

1 張會榮,劉松玉;地震液化引起的地面大變形對橋梁樁基的影響研究綜述[J];防災減災工程學報;2004年03期

2 王麗艷;劉漢龍;蔡艷;;用液化度概念評價巖土結(jié)構(gòu)地震液化變形的探討[J];防災減災工程學報;2007年04期

3 王志華;周恩全;徐超;;土體液化大變形研究進展與討論[J];南京工業(yè)大學學報(自然科學版);2012年05期

4 周健,劉寧;離心模型試驗技術(shù)應用的新進展[J];上海地質(zhì);2002年01期

5 莊海洋;陳國興;;砂土液化大變形本構(gòu)模型及在ABAQUS軟件上的實現(xiàn)[J];世界地震工程;2011年02期

6 張建民;砂土的可逆性和不可逆性剪脹規(guī)律[J];巖土工程學報;2000年01期

7 劉漢龍,周云東,高玉峰;砂土地震液化后大變形特性試驗研究[J];巖土工程學報;2002年02期

8 張建民;王剛;;砂土液化后大變形的機理[J];巖土工程學報;2006年07期

9 王剛;張建民;;砂土液化大變形的彈塑性循環(huán)本構(gòu)模型[J];巖土工程學報;2007年01期

10 王剛;張建民;;砂土液化變形的數(shù)值模擬[J];巖土工程學報;2007年03期

相關博士學位論文 前1條

1 王富強;自然排水條件下砂土液化變形規(guī)律與本構(gòu)模型研究[D];清華大學;2010年

，

本文編號：2158665