本文選題：軟土動力特性 + 離心模型試驗�。� 參考：《中國地震局工程力學研究所》2016年博士論文

【摘要】：軟土在動力作用下的非線性特征和地震動放大效應(yīng)是地震工程界一直以來關(guān)注和研究的熱點問題之一,由于當前已獲取的強震動觀測資料幾乎沒有軟土覆蓋的場地條件資料,使得軟土場地地震反應(yīng)分析結(jié)果無法用實際的強震記錄進行檢驗,因此軟土地區(qū)的抗震設(shè)計存在潛在的風險。針對近年來軟土動力特征以及自由場地震反應(yīng)分析存在的若干科學問題以及不確定性,本文通過理論分析、數(shù)值模擬和試驗研究相結(jié)合的手段,圍繞動荷載作用下軟土的動力特性及動強度特征、軟土在地震作用下的非線性特征和表現(xiàn)行為、軟土自由場的動態(tài)離心模型試驗分析、離心模擬與數(shù)值模擬比較及其驗證等四方面開展了理論分析和試驗研究。目標是試圖揭示軟土的動力學參數(shù)特征及在地震作用下的表現(xiàn)行為,評價軟土場地的抗震性能和動力災(zāi)變過程,合理地估計軟土場地地震動效應(yīng)問題,彌補由于強震動觀測資料的缺失導致理論計算無法驗證的這一現(xiàn)狀,推動軟土場地地震動效應(yīng)這一領(lǐng)域的研究,為我國軟土地區(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象,圍繞上述科學問題,開展的主要工作及研究創(chuàng)新如下:1.開展了軟土宏觀動力特征及微觀結(jié)構(gòu)的室內(nèi)試驗研究,分析了軟土的動力學特性、動強度特征以及微觀孔隙的定量化結(jié)果。針對典型軟土開展了常規(guī)物理力學性質(zhì)試驗、應(yīng)變控制和應(yīng)力控制條件下的循環(huán)動三軸試驗、微觀電子顯微鏡掃描試驗等描述宏觀動力特征和微觀結(jié)構(gòu)性的室內(nèi)試驗。研究在循環(huán)荷載作用下固結(jié)時間、有效圍壓、固結(jié)比等因素對軟土動力特性參數(shù),提出一套最優(yōu)化的擬合精度較高的試驗數(shù)據(jù)擬合方法,給出了天津軟土的G/Gmax-γ和λ-γ經(jīng)驗曲線;依據(jù)動強度試驗結(jié)果分析了軟土在不同動應(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.開展典型軟土和硬土自由場的大型土工離心機振動臺試驗,通過模擬強震臺站,獲取完整的加速度記錄,圍繞關(guān)鍵地震動參數(shù)進行數(shù)據(jù)分析,給出設(shè)定地震動的場地效應(yīng)。設(shè)計并構(gòu)造了軟土和硬土兩個均質(zhì)成層場地的離心模型,開展離心機振動臺試驗,并以此來人工模擬強震動觀測臺站,將天然地震波和人工地震波作為基底輸入,通過調(diào)整輸入峰值加速度來模擬不同強度的地震波,利用在模型箱中部和邊界布設(shè)加速度和位移傳感器,獲取軟土場地不同深度、不同層位監(jiān)測點的加速度峰值、時程、反應(yīng)譜、側(cè)向位移和沉降等量測結(jié)果,達到了利用離心模型試驗?zāi)M強震臺站并獲取完整記錄的試驗?zāi)繕撕托ЧＭㄟ^比對兩個離心模型試驗結(jié)果,研究表明相比于硬土而言,軟土具有強濾波和非線性特性,地震動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。試驗結(jié)果可與理論計算進行對比分析,進而達到離心模型試驗與數(shù)值模擬互為驗證的目的。3.編制可嵌入多種非線性滯回本構(gòu)模型的一維時域非線性地震反應(yīng)分析程序,通過將離心模型還原至原型場地,開展了軟土自由場非線性地震反應(yīng)分析。利用現(xiàn)有較為成熟的三種土體非線性動本構(gòu)模型(Davidenkov骨架曲線模型、“阻尼比退化系數(shù)”模型、“動態(tài)骨架曲線”模型),結(jié)合多次透射邊界條件和時域逐步遞推格式,編制可嵌入三種本構(gòu)模型的一維時域非線性地震反應(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)值模擬計算程序。依據(jù)離心模型,還原建立均質(zhì)成層的軟土場地和硬土場地原型,通過動三軸試驗給出與離心模型試驗土一致的動力學參數(shù),并以此建立軟土和硬土自由場的動力計算模型,開展多種算法的地震反應(yīng)數(shù)值模擬,計算給出典型自由場地表及地下層位的峰值加速度、時程、反應(yīng)譜以及地震動放大系數(shù)等。4.對動態(tài)離心模型試驗與多種數(shù)值模擬結(jié)果進行了互為比較和相互驗證,通過模擬強震臺站的離心模型試驗來驗證選取動本構(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,將動態(tài)離心模型試驗與多種數(shù)值模擬結(jié)果進行認真對比及差異分析,重點考察地表及地下層位的峰值加速度、反應(yīng)譜以及地震動放大系數(shù)的量測結(jié)果,比選和分析各土體時域非線性本構(gòu)模型的實效性,遴選出較適合軟土非線性特征的動本構(gòu)模型,進而達到與數(shù)值模擬互為驗證的目的,為今后開展軟土場地地震反應(yīng)分析提供新的思路和技術(shù)支撐。本文的學術(shù)貢獻和應(yīng)用價值:為軟土動力學研究提供了新的路徑,對軟土的動態(tài)離心模型試驗提供了經(jīng)驗,給出的天津濱海軟土的動力學參數(shù)對該地區(qū)工程抗震具有重要的應(yīng)用價值。
[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.

【學位授予單位】：中國地震局工程力學研究所
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TU435;P315.9

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