本文選題：吹填砂 + 海積軟土��； 參考：《廣西大學(xué)》2015年碩士論文

【摘要】：吹沙填海場地與自然沉積地塊具有截然不同的成因?qū)傩约肮こ虒傩�。原深厚的海積軟土變成新陸域大面積的軟弱下臥層；各土層欠固結(jié)且持續(xù)受外界因素擾動,“邊成型、邊固結(jié)、邊承載”；海積軟土直接覆蓋在海底基巖之上,由基巖導(dǎo)入的地震波可直接進入,加之這類地塊處于地震頻發(fā)地區(qū),是遠場強震產(chǎn)生長周期震害的“高風(fēng)險區(qū)”。故研究其動力特性對吹填地塊陸后工程防震減災(zāi)具有指示防范作用。本文以北部灣吹填場地軟土層的固結(jié)度和吹填砂層的密實度為切入點,以廣西防城港企沙填海區(qū)的吹填砂及海積軟土為研究對象。采用實驗室模擬技術(shù)制備不同密實程度下的土樣,并通過固結(jié)等常規(guī)力學(xué)實驗獲取吹填場地各土層的基本性能指標。利用ANSYS有限元軟件,分析不同密實程度下,吹沙填海場地卓越周期的演化特征及對基底垂直入射水平剪切波的動力響應(yīng)。并在給定吹填各土層密實程度的介質(zhì)框架內(nèi),研究各土層厚度對其動力特性及動力響應(yīng)的影響機理,為陸后工程建設(shè)提供依據(jù)。本文主要研究內(nèi)容及成果如下：1、通過對不同密實程度下的吹填場地進行模態(tài)分析可知：吹填場地各階固有頻率是呈線性增長的,且增長曲率與密實程度呈指數(shù)正相關(guān)關(guān)系；高階振型對場地動力作用影響劇烈,然其振型參與系數(shù)較小。且隨著場地土層密實程度的增大其水平振動所占的比例逐漸增大,豎向振動則反之,當密實程度達到一定值,扭轉(zhuǎn)振動所占的比例劇增且分值較大。2、施加水平地震加速度反應(yīng)譜,經(jīng)譜分析可知：隨著場地土層剛度的增加,節(jié)點位移越來越顯著尤其表現(xiàn)在中間軟土層區(qū)域,并逐漸往基巖方向發(fā)展,而吹填砂層振動位移表現(xiàn)出逐步緩慢穩(wěn)定的趨勢；場地卓越頻率逐漸往高頻率成分方向發(fā)展,且隨著土層密度的增大呈指數(shù)增長趨勢。3、基底垂直入射水平剪切波,經(jīng)地震時程分析可知：吹填場地對水平地震作用的放大效應(yīng)隨土層深度的變化十分顯著,并在吹填砂層表面達到最大值,但并不是與土層深度呈正相關(guān)關(guān)系。對豎向地震動中的長周期成分具有明顯的過濾作用,且隨著密實程度的增大,過濾作用越顯著,而對V/H譜比的影響反之。故對高層建筑進行抗震設(shè)計,應(yīng)充分考慮土層密實程度對其豎向地震動的影響。4、對不同海積軟土層厚度場地進行時程分析可知：地表峰值加速度放大效應(yīng)與土層厚度呈線性負相關(guān)關(guān)系,這是由于較厚的海積軟土層具有更大的隔振、濾波功能所致。反應(yīng)譜曲線存在兩個馬鞍形的雙峰,且隨著土層厚度的增加主導(dǎo)頻率由單峰逐漸向多峰演變,卓越周期成分的地震能量逐漸減小,場地卓越周期逐漸增大,對地震波的高頻部分減震作用增強,豎向地震放大效應(yīng)逐漸減小。5、對不同吹填砂層厚度場地進行時程分析可知：地震放大效應(yīng)隨著吹填砂層厚度的增加而減小,場地卓越周期逐漸往短周期方向發(fā)展；當吹砂層厚度增大到某一值后,再繼續(xù)增加吹砂層厚度,地震響應(yīng)放大倍數(shù)反而會增加,此時場地會出現(xiàn)多個卓越周期,不利于工程抗震設(shè)防。
[Abstract]:The sand blowing site and the natural sedimentary block have distinct genetic attributes and engineering properties. The original deep sea soft soil is transformed into a weak subsurface layer with large area of the new land area; the soil layers are under consolidation and are constantly disturbed by external factors, "edge forming, side consolidation, side bearing", and the soft soil is covered by the base rock on the bottom of the bottom of the sea floor. The seismic waves introduced are directly entered, and this kind of block is in the area of frequent earthquake occurrence, which is a "high risk zone" for the earthquake damage of the long field strong earthquake production. Therefore, the study of its dynamic characteristics has a directive and preventive effect on the earthquake prevention and disaster reduction of the land after land engineering of the dredger fill massif. As the breakthrough point, taking the dredger sand and the soft soil in the Fangchenggang reclamation area of Guangxi as the research object, the soil samples with different compaction degree are prepared by the laboratory simulation technology, and the basic performance indexes of each soil layer in the filling site are obtained by the consolidation and other conventional mechanics experiments. The ANSYS finite element software is used to analyze the different compaction degree. The evolution characteristics of the excellent period of sand reclamation and the dynamic response to the horizontal shear wave of the vertical incident on the base, and the mechanism of the influence of the thickness of the soil layer on the dynamic characteristics and dynamic response of each soil layer in the medium frame of the density of the soil layers of the given fill, are provided for the construction of the post land engineering. The main contents and results of this paper are as follows 1, through the modal analysis of the filling site under different compaction degrees, it is found that the natural frequencies of each order of the filling site are linearly increasing, and the growth curvature and the degree of compactness are exponentially positively correlated; the high order modes have a strong influence on the dynamic action of the site, but the coefficient of the vibration mode is smaller. The proportion of the horizontal vibration increases gradually, and the vertical vibration is the opposite. When the density reaches a certain value, the proportion of the torsional vibration increases sharply and the value is larger.2. The horizontal seismic acceleration response spectrum is applied. The spectrum analysis shows that with the increase of the soil layer stiffness, the node displacement is becoming more and more obvious in the middle soft soil. The layer area is progressively developing in the direction of the bedrock, and the vibration displacement of the fill sand layer shows a gradual and steady trend; the site excellent frequency gradually develops to the high frequency component, and increases exponentially with the increase of the soil density. The vertical incident shear wave in the basement can be seen by the seismic time history analysis. The amplification effect of the horizontal earthquake is very significant with the depth of the soil layer, and the maximum value is reached on the surface of the sand layer, but it is not positively correlated with the depth of the soil layer. It has obvious filtration effect on the long period components in the vertical ground motion, and the effect of filtration is more significant with the increase of the density, and the effect on the V/H spectrum ratio On the contrary, the seismic design of high rise buildings should take full account of the influence of the degree of soil compaction on its vertical ground motion,.4. The time history analysis of different sea floor thickness sites shows that the amplification effect of the surface peak acceleration and the thickness of the soil layer has a linear negative correlation, which is due to the thicker soft soil layer. There are two saddle shaped Shuangfeng in the response spectrum curve. With the increase of the thickness of the soil, the dominant frequency gradually evolves from single peak to multi peak. The earthquake energy of the excellent periodic component gradually decreases, the site excellent period gradually increases, the high frequency part of the seismic wave is enhanced and the vertical seismic amplification effect is gradually increased. With the reduction of.5, the time history analysis of the thickness of different sand bed thickness shows that the seismic amplification effect decreases with the increase of the thickness of the dredger fill sand layer, and the excellent period of the site gradually develops to the short period. There will be many remarkable periods in the site, which will be unfavorable for earthquake protection.
【學(xué)位授予單位】：廣西大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU435

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本文編號：1907845