本文選題：軟土動(dòng)力特性 + 離心模型試驗(yàn)��； 參考：《中國(guó)地震局工程力學(xué)研究所》2016年博士論文

【摘要】：軟土在動(dòng)力作用下的非線性特征和地震動(dòng)放大效應(yīng)是地震工程界一直以來(lái)關(guān)注和研究的熱點(diǎn)問(wèn)題之一,由于當(dāng)前已獲取的強(qiáng)震動(dòng)觀測(cè)資料幾乎沒(méi)有軟土覆蓋的場(chǎng)地條件資料,使得軟土場(chǎng)地地震反應(yīng)分析結(jié)果無(wú)法用實(shí)際的強(qiáng)震記錄進(jìn)行檢驗(yàn),因此軟土地區(qū)的抗震設(shè)計(jì)存在潛在的風(fēng)險(xiǎn)。針對(duì)近年來(lái)軟土動(dòng)力特征以及自由場(chǎng)地震反應(yīng)分析存在的若干科學(xué)問(wèn)題以及不確定性,本文通過(guò)理論分析、數(shù)值模擬和試驗(yàn)研究相結(jié)合的手段,圍繞動(dòng)荷載作用下軟土的動(dòng)力特性及動(dòng)強(qiáng)度特征、軟土在地震作用下的非線性特征和表現(xiàn)行為、軟土自由場(chǎng)的動(dòng)態(tài)離心模型試驗(yàn)分析、離心模擬與數(shù)值模擬比較及其驗(yàn)證等四方面開(kāi)展了理論分析和試驗(yàn)研究。目標(biāo)是試圖揭示軟土的動(dòng)力學(xué)參數(shù)特征及在地震作用下的表現(xiàn)行為,評(píng)價(jià)軟土場(chǎng)地的抗震性能和動(dòng)力災(zāi)變過(guò)程,合理地估計(jì)軟土場(chǎng)地地震動(dòng)效應(yīng)問(wèn)題,彌補(bǔ)由于強(qiáng)震動(dòng)觀測(cè)資料的缺失導(dǎo)致理論計(jì)算無(wú)法驗(yàn)證的這一現(xiàn)狀,推動(dòng)軟土場(chǎng)地地震動(dòng)效應(yīng)這一領(lǐng)域的研究,為我國(guó)軟土地區(qū)工程抗震設(shè)防提供參考依據(jù)。在充分吸收總結(jié)前人已有成果的基礎(chǔ)上,本文以天津地區(qū)濱海相軟土為研究對(duì)象,圍繞上述科學(xué)問(wèn)題,開(kāi)展的主要工作及研究創(chuàng)新如下:1.開(kāi)展了軟土宏觀動(dòng)力特征及微觀結(jié)構(gòu)的室內(nèi)試驗(yàn)研究,分析了軟土的動(dòng)力學(xué)特性、動(dòng)強(qiáng)度特征以及微觀孔隙的定量化結(jié)果。針對(duì)典型軟土開(kāi)展了常規(guī)物理力學(xué)性質(zhì)試驗(yàn)、應(yīng)變控制和應(yīng)力控制條件下的循環(huán)動(dòng)三軸試驗(yàn)、微觀電子顯微鏡掃描試驗(yàn)等描述宏觀動(dòng)力特征和微觀結(jié)構(gòu)性的室內(nèi)試驗(yàn)。研究在循環(huán)荷載作用下固結(jié)時(shí)間、有效圍壓、固結(jié)比等因素對(duì)軟土動(dòng)力特性參數(shù),提出一套最優(yōu)化的擬合精度較高的試驗(yàn)數(shù)據(jù)擬合方法,給出了天津軟土的G/Gmax-γ和λ-γ經(jīng)驗(yàn)曲線;依據(jù)動(dòng)強(qiáng)度試驗(yàn)結(jié)果分析了軟土在不同動(dòng)應(yīng)力幅值作用下累積塑性應(yīng)變、雙幅應(yīng)變與循環(huán)振次的關(guān)系;利用電鏡掃描技術(shù)開(kāi)展軟土單元體試樣的微觀結(jié)構(gòu)分析,定量地描述軟土的微觀結(jié)構(gòu)特征。2.開(kāi)展典型軟土和硬土自由場(chǎng)的大型土工離心機(jī)振動(dòng)臺(tái)試驗(yàn),通過(guò)模擬強(qiáng)震臺(tái)站,獲取完整的加速度記錄,圍繞關(guān)鍵地震動(dòng)參數(shù)進(jìn)行數(shù)據(jù)分析,給出設(shè)定地震動(dòng)的場(chǎng)地效應(yīng)。設(shè)計(jì)并構(gòu)造了軟土和硬土兩個(gè)均質(zhì)成層場(chǎng)地的離心模型,開(kāi)展離心機(jī)振動(dòng)臺(tái)試驗(yàn),并以此來(lái)人工模擬強(qiáng)震動(dòng)觀測(cè)臺(tái)站,將天然地震波和人工地震波作為基底輸入,通過(guò)調(diào)整輸入峰值加速度來(lái)模擬不同強(qiáng)度的地震波,利用在模型箱中部和邊界布設(shè)加速度和位移傳感器,獲取軟土場(chǎng)地不同深度、不同層位監(jiān)測(cè)點(diǎn)的加速度峰值、時(shí)程、反應(yīng)譜、側(cè)向位移和沉降等量測(cè)結(jié)果,達(dá)到了利用離心模型試驗(yàn)?zāi)M強(qiáng)震臺(tái)站并獲取完整記錄的試驗(yàn)?zāi)繕?biāo)和效果。通過(guò)比對(duì)兩個(gè)離心模型試驗(yàn)結(jié)果,研究表明相比于硬土而言,軟土具有強(qiáng)濾波和非線性特性,地震動(dòng)從底部至地表能量和幅值有一定的損失和衰減,峰值加速度總體上呈現(xiàn)先增大后縮小的趨勢(shì)。試驗(yàn)結(jié)果可與理論計(jì)算進(jìn)行對(duì)比分析,進(jìn)而達(dá)到離心模型試驗(yàn)與數(shù)值模擬互為驗(yàn)證的目的。3.編制可嵌入多種非線性滯回本構(gòu)模型的一維時(shí)域非線性地震反應(yīng)分析程序,通過(guò)將離心模型還原至原型場(chǎng)地,開(kāi)展了軟土自由場(chǎng)非線性地震反應(yīng)分析。利用現(xiàn)有較為成熟的三種土體非線性動(dòng)本構(gòu)模型(Davidenkov骨架曲線模型、“阻尼比退化系數(shù)”模型、“動(dòng)態(tài)骨架曲線”模型),結(jié)合多次透射邊界條件和時(shí)域逐步遞推格式,編制可嵌入三種本構(gòu)模型的一維時(shí)域非線性地震反應(yīng)分析程序包,形成以不同本構(gòu)模型方案為基礎(chǔ)的數(shù)值模擬計(jì)算程序。依據(jù)離心模型,還原建立均質(zhì)成層的軟土場(chǎng)地和硬土場(chǎng)地原型,通過(guò)動(dòng)三軸試驗(yàn)給出與離心模型試驗(yàn)土一致的動(dòng)力學(xué)參數(shù),并以此建立軟土和硬土自由場(chǎng)的動(dòng)力計(jì)算模型,開(kāi)展多種算法的地震反應(yīng)數(shù)值模擬,計(jì)算給出典型自由場(chǎng)地表及地下層位的峰值加速度、時(shí)程、反應(yīng)譜以及地震動(dòng)放大系數(shù)等。4.對(duì)動(dòng)態(tài)離心模型試驗(yàn)與多種數(shù)值模擬結(jié)果進(jìn)行了互為比較和相互驗(yàn)證,通過(guò)模擬強(qiáng)震臺(tái)站的離心模型試驗(yàn)來(lái)驗(yàn)證選取動(dòng)本構(gòu)模型的合理性以及數(shù)值模擬方法的可行性。在上述研究成果的基礎(chǔ)上,將動(dòng)態(tài)離心模型試驗(yàn)與多種數(shù)值模擬結(jié)果進(jìn)行認(rèn)真對(duì)比及差異分析,重點(diǎn)考察地表及地下層位的峰值加速度、反應(yīng)譜以及地震動(dòng)放大系數(shù)的量測(cè)結(jié)果,比選和分析各土體時(shí)域非線性本構(gòu)模型的實(shí)效性,遴選出較適合軟土非線性特征的動(dòng)本構(gòu)模型,進(jìn)而達(dá)到與數(shù)值模擬互為驗(yàn)證的目的,為今后開(kāi)展軟土場(chǎng)地地震反應(yīng)分析提供新的思路和技術(shù)支撐。本文的學(xué)術(shù)貢獻(xiàn)和應(yīng)用價(jià)值:為軟土動(dòng)力學(xué)研究提供了新的路徑,對(duì)軟土的動(dòng)態(tài)離心模型試驗(yàn)提供了經(jīng)驗(yàn),給出的天津?yàn)I海軟土的動(dòng)力學(xué)參數(shù)對(duì)該地區(qū)工程抗震具有重要的應(yīng)用價(jià)值。
[Abstract]:The nonlinear characteristics of soft soil under dynamic action and the amplification effect of ground motion are one of the hot issues that have been concerned and studied by the earthquake engineering circle. Because there is almost no ground condition data of soft soil covered by the strong seismic observation data obtained at present, the results of the seismic response analysis of the soft soil site can not be recorded by the actual strong earthquake. The seismic design of soft soil area has a potential risk. Aiming at some scientific problems and uncertainties existing in the dynamic characteristics of soft soil and the analysis of the seismic response of free field in recent years, the dynamic characteristics and dynamic characteristics of soft soil under dynamic load are discussed by means of theoretical analysis, numerical simulation and experimental research. The characteristics of strength, nonlinear characteristics and behavior of soft soil under earthquake action, dynamic centrifugal model test and analysis of soft soil free field, comparison between centrifugal simulation and numerical simulation and its verification are carried out in four aspects. The aim is to reveal the characteristics of dynamic parameters of soft soil and its performance under earthquake action. In order to evaluate the seismic performance and dynamic catastrophe process of soft soil site, to estimate the ground motion effect in soft soil site, to make up for the present situation that the theoretical calculation can not be verified due to the lack of observation data of strong vibration, and to promote the research in the field of ground vibration effect in soft soil site, to provide reference for the seismic fortification of the soft soil area in China. On the basis of fully absorbing the previous achievements of the predecessors, this paper takes the coastal soft soil in Tianjin as the research object. The main work and research innovation around the above scientific problems are as follows: 1. the indoor experimental research on the dynamic characteristics and microstructure of the soft soil was carried out, and the dynamic characteristics and dynamic strength of the soft soil were analyzed. Characteristics and the quantitative results of microscopic pores. In the typical soft soil, the conventional physical and mechanical properties test, cyclic three axis test under strain control and stress control, micro electron microscope scanning test, and other indoor experiments describing macroscopic dynamic characteristics and microstructure are carried out, and the consolidation time under cyclic loading is studied. A set of optimal fitting methods of experimental data fitting is proposed for soft soil dynamic characteristic parameters, such as effective confining pressure and consolidation ratio, and the G/Gmax- gamma and lambda gamma experience curve of Tianjin soft soil is given. According to the dynamic strength test results, the cumulative plastic strain, double amplitude strain and cycle under the action of different dynamic stress amplitude are analyzed. The analysis of the microstructure of the soft soil unit samples by the scanning electron microscope and the quantitative description of the microstructure characteristics of the soft soil.2. to carry out the large geotechnical centrifuge shaking table test of the typical soft soil and the hard soil free field. Through the simulation of the strong seismic station, the complete acceleration records are obtained, and the key ground vibration parameters are carried out. A centrifuge model of two homogeneous layer sites of soft soil and hard soil is designed and constructed. The centrifuge shaking table test is carried out to simulate the strong vibration observation station. Natural seismic waves and artificial seismic waves are used as base inputs and the input peak acceleration is adjusted to simulate the input peak acceleration. The acceleration and displacement sensors are set up in the middle and boundary of the model box to obtain the acceleration peak, time history, response spectrum, lateral displacement and settlement of the monitoring points of different layers, and the test of simulating strong earthquake stations and obtaining a complete record by centrifugal model test is achieved. By comparing the results of two centrifuge models, it is shown that the soft soil has strong filtering and nonlinear characteristics compared with the hard soil, and the ground motion has a certain loss and attenuation from the bottom to the surface, and the peak acceleration tends to increase first and then reduce. The experimental results can be carried out with the theoretical calculation. Comparative analysis, and then to achieve the purpose of mutual validation between centrifugal model test and numerical simulation.3., a one-dimensional nonlinear seismic response analysis program which can be embedded in a variety of nonlinear hysteretic constitutive models is developed. By reducing the centrifuge model to the prototype site, the non linear seismic response analysis of soft soil free field is carried out. Three kinds of soil nonlinear dynamic constitutive models (Davidenkov skeleton curve model, damping ratio degradation coefficient "model," dynamic skeleton curve "model), combined with multiple transmission boundary conditions and time domain recursive scheme, a one-dimensional time-domain nonlinear seismic response analysis program which can be embedded into three constitutive models is developed to form different constitutive models. The model based numerical simulation program is based on the centrifuge model. Based on the centrifugal model, the soft soil site and the prototype of the hard soil site are reduced. The dynamic parameters consistent with the centrifuge model test soil are given by the dynamic three axis test, and the dynamic calculation model of the free field and the free field of the soft soil and the hard soil is established, and the seismic responses of various algorithms are carried out. The numerical simulation is used to calculate the peak acceleration, time history, response spectrum and seismic amplification factor of the surface and underground layers of the typical free field. The dynamic centrifugal model test and a variety of numerical simulation results are compared and verified each other. The dynamic model test is used to verify the selection of the dynamic constitutive model by simulating the centrifugal model test of the strong earthquake station. On the basis of the above research results, the dynamic centrifugal model test and a variety of numerical simulation results are carefully contrasted and different, and the peak acceleration, the response spectrum and the large coefficient of seismic dynamic discharge are investigated, which are compared to the selection and analysis of soil mass. The effectiveness of the domain nonlinear constitutive model is to select the dynamic constitutive model suitable for the nonlinear characteristics of the soft soil, and then to achieve the purpose of mutual validation with the numerical simulation, and provide new ideas and technical support for the seismic response analysis of soft soil sites in the future. The academic contribution and Application value of this paper provide a new method for the research of soft soil dynamics. The path has provided experience for the dynamic centrifugal model test of soft soil. The dynamic parameters of Tianjin coastal soft soil are of great value to the earthquake resistance in this area.

【學(xué)位授予單位】：中國(guó)地震局工程力學(xué)研究所
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TU435;P315.9

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本文編號(hào)：1882166