本文選題：樁基檢測 + 聲波透射法��； 參考：《南昌航空大學(xué)》2017年碩士論文

【摘要】：隨著我國建設(shè)工程的快速增長,大直徑、超長混凝土樁基在城市建設(shè)、橋梁工程中得到廣泛應(yīng)用,樁基質(zhì)量直接影響建筑物及橋梁的安全可靠性,因此樁基質(zhì)量檢測具有重要的現(xiàn)實意義。聲波透射法主要是通過聲波能量的衰減、波速和主頻的變化以及波形的畸變等來判斷聲波傳播路徑上的混凝土質(zhì)量,具有檢測高效、結(jié)果可靠、不受樁長限制等優(yōu)點,已成為樁基完整性檢測的重要手段。本文通過有限元波動法模擬聲波在樁身內(nèi)傳播,從而對獲得的多種聲學(xué)參數(shù)進行時域和頻域分析,研究缺陷混凝土樁基中聲波的傳播規(guī)律。將聲波層析成像技術(shù)應(yīng)用于大直徑樁基檢測中,利用聲時信息來反演樁基內(nèi)部質(zhì)量狀況,為聲波層析成像技術(shù)檢測樁基缺陷提供可靠依據(jù)。主要研究內(nèi)容及結(jié)論如下:(1)介紹了樁基透射波法檢測技術(shù)的基本原理和信號分析方法,對聲波層析成像技術(shù)在樁基檢測中的理論基礎(chǔ)、成像思路和成像反演算法進行了歸納總結(jié),為后續(xù)的有限元模擬研究提供理論依據(jù)。(2)通過ANSYS/LS-DYNA有限元軟件模擬聲波在大直徑樁基中傳播,避免了樁基聲波檢測過程中傳感器耦合不佳及噪音干擾的影響,通過波速的計算驗證了利用有限元法計算樁身波動問題的準確性;分析了聲波在缺陷混凝土中傳播特性與缺陷線性尺寸變化的關(guān)系;對不同缺陷類型樁基接收信號進行了時域、頻域分析,并對頻譜畸變系數(shù)進行了研究,探討豎向線性尺寸、水平方向線性尺寸、孔洞尺寸及材料參數(shù)對聲波接收信號時域及頻域的影響規(guī)律。研究表明:本文所選取的聲波震源頻譜能量集中,適用于大直徑樁基信號檢測分析;缺陷豎向線性尺寸、孔洞尺寸及材料參數(shù)對波速、波幅及主頻幅值影響較大,缺陷水平方向線性尺寸對波速、波幅及主頻幅值影響較小;頻譜畸變系數(shù)能夠靈敏地反映頻譜能量的衰減,不同缺陷類型之間頻譜畸變系數(shù)差異十分明顯。(3)針對樁基檢測的特殊性及復(fù)雜性,對樁基聲波層析成像檢測步驟進行了系統(tǒng)的介紹;利用有限元軟件建立不同樁徑的缺陷樁基模型,對聲波在混凝土樁基中的傳播進行模擬,以接收點首波走時為反演參數(shù)對樁身進行反演成像,對比分析聲波頻率分別為50kHz和100kHz的聲波層析成像反演結(jié)果;建立含不同尺寸缺陷的樁基模型,模擬聲波在缺陷樁基中的傳播,對比分析平測和斜測兩種觀測系統(tǒng)的聲波層析成像反演結(jié)果。研究表明:50kHz適合作為大直徑樁基聲波層析成像震源頻率,100kHz適合作為1m以下直徑樁基層析成像震源頻率;矩形缺陷水平方向尺寸在0.4m以內(nèi)時,采用平測觀測系統(tǒng)的聲波CT成像效果較好,當(dāng)缺陷水平方向尺寸大于0.4m時,宜采用斜測觀測系統(tǒng)進行聲波CT成像。
[Abstract]:With the rapid growth of construction projects in China, large diameter and super-long concrete pile foundation is widely used in urban construction and bridge engineering. The quality of pile foundation directly affects the safety and reliability of buildings and bridges. Therefore, pile foundation quality detection has important practical significance. The acoustic transmission method is mainly based on the attenuation of acoustic wave energy, the variation of wave velocity and main frequency, and the distortion of wave form to judge the quality of concrete on the sound wave propagation path. It has the advantages of high efficiency, reliable results and not limited by the length of pile, etc. It has become an important means to check the integrity of pile foundation. In this paper, the finite element wave method is used to simulate the sound wave propagation in the pile body, so as to analyze the acoustic parameters in time domain and frequency domain, and to study the propagation law of acoustic wave in the pile foundation of defective concrete. The acoustic tomography technique is applied to the detection of large diameter pile foundation, and the acoustic time information is used to retrieve the internal quality of the pile foundation, which provides a reliable basis for detecting the defect of the pile foundation by the acoustic wave tomography technology. The main research contents and conclusions are as follows: (1) the basic principle and signal analysis method of pile foundation transmission wave detection technology are introduced, and the theoretical basis of acoustic wave tomography technology in pile foundation detection is discussed. The imaging idea and imaging inversion algorithm are summarized, which provides a theoretical basis for the subsequent finite element simulation research. (2) the sound wave propagation in large diameter pile foundation is simulated by ANSYS/LS-DYNA finite element software. In order to avoid the influence of poor coupling of sensors and noise interference in the detection process of acoustic wave of pile foundation, the accuracy of calculating the wave problem of pile body by finite element method is verified by the calculation of wave velocity. The relationship between the propagation characteristics of acoustic waves in the defect concrete and the change of the linear size of the defect is analyzed, and the time domain and frequency domain analysis of the received signals of the pile foundation with different defect types are carried out, and the spectrum distortion coefficient is studied, and the vertical linear size is discussed. The influence of horizontal linear dimension, hole size and material parameters on the time domain and frequency domain of acoustic wave receiving signal. The results show that the frequency spectrum of the acoustic source selected in this paper is suitable for detecting and analyzing the signal of large diameter pile foundation, and the vertical linear size of defect, the size of hole and material parameters have great influence on the wave velocity, amplitude and amplitude of main frequency. The linear dimension of the horizontal direction of the defect has little effect on the wave velocity, amplitude and main frequency amplitude, and the spectrum distortion coefficient can reflect the attenuation of the spectrum energy sensitively. According to the particularity and complexity of pile foundation detection, this paper systematically introduces the detecting steps of pile foundation acoustic wave tomography. The finite element software is used to establish the defective pile foundation model with different diameter of pile. The propagation of acoustic wave in concrete pile foundation is simulated, and the inversion imaging of the pile body is carried out using the first wave travel time of the receiving point as the inversion parameter. The inversion results of acoustic wave tomography with frequency of 50kHz and 100kHz are compared and analyzed, and the model of pile foundation with different size defects is established to simulate the propagation of acoustic wave in the defective pile foundation. The inversion results of acoustic tomography in two observation systems, flat and oblique, are compared and analyzed. The results show that: 50 kHz is suitable for large diameter pile foundation acoustic tomography focal frequency and 100 kHz for pile foundation tomography source frequency below 1m, when the horizontal dimension of rectangular defect is less than 0.4 m, When the horizontal dimension of the defect is greater than 0.4 m, the oblique observation system is suitable for acoustic CT imaging.
【學(xué)位授予單位】：南昌航空大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU473.16

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