子波在節(jié)理巖體中的傳播規(guī)律及其應(yīng)用
發(fā)布時(shí)間：2018-10-13 10:09
【摘要】：準(zhǔn)確獲取巖體變形參數(shù)對(duì)于分析巖體工程的變形和穩(wěn)定性具有重要意義。子波在巖體中傳播時(shí)振幅譜和相位譜發(fā)生變化，綜合體現(xiàn)為波形變化，因而子波波形變化比波速、振幅和頻率等參數(shù)能更全面靈敏反映巖體力學(xué)參數(shù)。本文采用理論分析、現(xiàn)場(chǎng)試驗(yàn)和數(shù)值計(jì)算等多種研究手段，研究子波在黏彈性巖層、黏彈性節(jié)理、層狀巖體和節(jié)理巖體的傳播規(guī)律，提出了節(jié)理剛度的波動(dòng)測(cè)試方法，并討論了該方法的測(cè)試誤差和適用條件，研究的主要結(jié)論如下。 （1）Kelvin介質(zhì)的選擇性吸收引起子波的頻譜特性發(fā)生變化，隨傳播距離增加，子波的特征頻率和帶寬減小，特征頻率呈負(fù)指數(shù)規(guī)律減小，并趨于穩(wěn)定值，，進(jìn)而引起子波振幅減小和振動(dòng)持時(shí)增加；隨著彈性模量減小或者介質(zhì)的黏滯性增加，形成子波波形相對(duì)穩(wěn)定的距離減小。 （2）節(jié)理質(zhì)量對(duì)P波在節(jié)理的透射系數(shù)和反射系數(shù)有重要影響，不考慮節(jié)理質(zhì)量時(shí)，采用位移不連續(xù)模型計(jì)算得到的P波反射系數(shù)、SV波透射系數(shù)和反射系數(shù)都偏大，而P波透射系數(shù)明顯偏小，隨節(jié)理厚度增加，偏差增加；黏彈性節(jié)理的選擇性吸收引起透射波振幅減小，主瓣不突出，分辨率減小，波形相關(guān)系數(shù)和波形變化系數(shù)能夠有效反映子波傳過(guò)節(jié)理的波形變化，相對(duì)切向剛度和切向黏性系數(shù)，節(jié)理的法向剛度和法向黏性系數(shù)對(duì)子波波形變化影響更大。 （3）彈性層狀巖體具有多尺度梳狀濾波器的特性，隨巖層厚度與波長(zhǎng)之比增加，由層內(nèi)多重透、反射引起振幅透射系數(shù)和反射系數(shù)成大尺度周期性變化，大尺度周期為=0.5，在一個(gè)大尺度周期內(nèi)存在一個(gè)帶通和一個(gè)帶阻，在帶通內(nèi)又存在多個(gè)小尺度周期，是由層間多重透、反射形成的，黏彈性層狀巖體總體表現(xiàn)為低通濾波，在低通濾波范圍內(nèi)存在多個(gè)帶通和帶阻。 （4）不同頻率范圍內(nèi)的應(yīng)力波在巖體的傳播過(guò)程中，衰減系數(shù)對(duì)頻率的依賴性具有顯著差異，完整巖體總體上表現(xiàn)為低通濾波，在低通濾波范圍內(nèi)具有非等間距帶通濾波特性，在吸收頻率過(guò)渡帶，應(yīng)力波衰減系數(shù)隨頻率變化非常快，黏性系數(shù)非定常Maxwell模型能夠有效描述應(yīng)力波在完整巖體中的衰減系數(shù)變化規(guī)律；巖體越破碎，濾波能力越強(qiáng)，低通范圍越小，吸收頻率過(guò)渡帶陡度參數(shù)越小。 （5）根據(jù)子波傳過(guò)節(jié)理的波形變化規(guī)律提出節(jié)理剛度測(cè)試方法，該方法具有很好的重復(fù)性，當(dāng)節(jié)理厚度小于0.1m，測(cè)試誤差小于15.0%，研究結(jié)果表明，隨測(cè)點(diǎn)與節(jié)理間的距離增加，測(cè)試誤差先減小后增加，存在一個(gè)合理測(cè)點(diǎn)布置位置，通過(guò)數(shù)值計(jì)算和現(xiàn)場(chǎng)試驗(yàn)確定測(cè)點(diǎn)與節(jié)理間的合理距離為10~20cm。
[Abstract]:It is very important to obtain the deformation parameters of rock mass accurately for analyzing the deformation and stability of rock mass engineering. When wavelet propagates in rock mass, the amplitude spectrum and phase spectrum change, which is reflected by waveform change. Therefore, wavelet waveform can reflect more fully and sensitively the mechanical parameters of rock mass than the parameters of wave velocity, amplitude and frequency. In this paper, the propagation law of wavelet in viscoelastic strata, viscoelastic joints, layered rock mass and jointed rock mass is studied by means of theoretical analysis, field test and numerical calculation. The main conclusions are as follows: (1) selective absorption of Kelvin medium causes the variation of wavelet spectrum characteristics, and the characteristic frequency and bandwidth decrease with the increase of propagation distance. The characteristic frequency decreases exponentially and tends to be stable, which leads to the decrease of wavelet amplitude and the increase of vibration duration, with the decrease of elastic modulus or the increase of the viscosity of the medium. (2) the mass of joint has an important effect on the transmission coefficient and reflection coefficient of P wave in joint, and when the mass of joint is not considered, The reflection coefficient of P wave calculated by discontinuous displacement model, the transmission coefficient and reflection coefficient of SV wave are larger, but the transmission coefficient of P wave is obviously smaller, and the deviation increases with the increase of joint thickness. The selective absorption of viscoelastic joints causes the amplitude of transmission wave to decrease, the main lobe is not prominent, and the resolution decreases. The correlation coefficient and variation coefficient of waveform can effectively reflect the waveform changes of wavelet transmitted joints. Relative to tangential stiffness and tangential viscosity coefficient, normal stiffness and normal viscosity coefficient of joints have more influence on wavelet waveform change. (3) Elastic layered rock mass has the characteristics of multi-scale comb filter. With the increase of the ratio of rock thickness to wavelength, the amplitude, transmission coefficient and reflection coefficient change periodically on a large scale with a large scale period = 0.5. There is a bandpass and a band barrier in a large scale period. There are many small scale periods in the bandpass, which are formed by interlayer multiple permeation and reflection. The viscoelastic layered rock mass is characterized by low pass filtering. There are many bandpass and band-stop in the low pass filtering range. (4) in the propagation process of stress wave in different frequency range, there are significant differences in the dependence of attenuation coefficient on frequency, and the whole rock mass is characterized by low pass filter. In the range of low-pass filtering, it has the characteristic of non-equal-spacing band-pass filtering. In the transition zone of absorption frequency, the attenuation coefficient of stress wave changes very quickly with the frequency. The unsteady Maxwell model of viscosity coefficient can effectively describe the attenuation coefficient of stress wave in intact rock mass, the more broken rock mass, the stronger the filtering ability and the smaller the low pass range. The steepness parameter of the transition band of absorption frequency is smaller. (5) according to the variation law of wavelet transmitted joint waveform, the method of joint stiffness measurement is presented, which has good repeatability. When the thickness of joints is less than 0.1 m and the measurement error is less than 15.0, the results show that with the increase of the distance between the measured points and joints, the measurement errors decrease first and then increase, and there is a reasonable location of measuring points. The reasonable distance between the measured point and the joint is determined to be 10 ~ 20 cm by numerical calculation and field test.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)（北京）
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU452
本文編號(hào)：2268224
[Abstract]:It is very important to obtain the deformation parameters of rock mass accurately for analyzing the deformation and stability of rock mass engineering. When wavelet propagates in rock mass, the amplitude spectrum and phase spectrum change, which is reflected by waveform change. Therefore, wavelet waveform can reflect more fully and sensitively the mechanical parameters of rock mass than the parameters of wave velocity, amplitude and frequency. In this paper, the propagation law of wavelet in viscoelastic strata, viscoelastic joints, layered rock mass and jointed rock mass is studied by means of theoretical analysis, field test and numerical calculation. The main conclusions are as follows: (1) selective absorption of Kelvin medium causes the variation of wavelet spectrum characteristics, and the characteristic frequency and bandwidth decrease with the increase of propagation distance. The characteristic frequency decreases exponentially and tends to be stable, which leads to the decrease of wavelet amplitude and the increase of vibration duration, with the decrease of elastic modulus or the increase of the viscosity of the medium. (2) the mass of joint has an important effect on the transmission coefficient and reflection coefficient of P wave in joint, and when the mass of joint is not considered, The reflection coefficient of P wave calculated by discontinuous displacement model, the transmission coefficient and reflection coefficient of SV wave are larger, but the transmission coefficient of P wave is obviously smaller, and the deviation increases with the increase of joint thickness. The selective absorption of viscoelastic joints causes the amplitude of transmission wave to decrease, the main lobe is not prominent, and the resolution decreases. The correlation coefficient and variation coefficient of waveform can effectively reflect the waveform changes of wavelet transmitted joints. Relative to tangential stiffness and tangential viscosity coefficient, normal stiffness and normal viscosity coefficient of joints have more influence on wavelet waveform change. (3) Elastic layered rock mass has the characteristics of multi-scale comb filter. With the increase of the ratio of rock thickness to wavelength, the amplitude, transmission coefficient and reflection coefficient change periodically on a large scale with a large scale period = 0.5. There is a bandpass and a band barrier in a large scale period. There are many small scale periods in the bandpass, which are formed by interlayer multiple permeation and reflection. The viscoelastic layered rock mass is characterized by low pass filtering. There are many bandpass and band-stop in the low pass filtering range. (4) in the propagation process of stress wave in different frequency range, there are significant differences in the dependence of attenuation coefficient on frequency, and the whole rock mass is characterized by low pass filter. In the range of low-pass filtering, it has the characteristic of non-equal-spacing band-pass filtering. In the transition zone of absorption frequency, the attenuation coefficient of stress wave changes very quickly with the frequency. The unsteady Maxwell model of viscosity coefficient can effectively describe the attenuation coefficient of stress wave in intact rock mass, the more broken rock mass, the stronger the filtering ability and the smaller the low pass range. The steepness parameter of the transition band of absorption frequency is smaller. (5) according to the variation law of wavelet transmitted joint waveform, the method of joint stiffness measurement is presented, which has good repeatability. When the thickness of joints is less than 0.1 m and the measurement error is less than 15.0, the results show that with the increase of the distance between the measured points and joints, the measurement errors decrease first and then increase, and there is a reasonable location of measuring points. The reasonable distance between the measured point and the joint is determined to be 10 ~ 20 cm by numerical calculation and field test.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)（北京）
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU452
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