| For recognize deep engineering environment complex rock mass mechanics behavior, we carried out physical modeling experiment and infrared detection to study the layered sedimentary rock mass with different angle. We take horizontal stratified rock masses and 45? inclined stratified rock masses as the research object. Through to the infrared image processing, obtained averaged infrared radiation temperature curve to characterize the overall mechanical behavior of the stressed rock masses, the processed infrared image reveal the nonlinear structure of rock mass effect and the Fourier spectra describe the stress wave propagation in rock masses. Further reveals the stratified rock masses roadways deformation and failure processes mechanics behavior under the condition of high stress.In order to process the noisy and low-contrast infrared image, new image processing algorithm was proposed which consist of the following operations: image subtraction for removal of the environmental radiation noise, median filter for reduction of the pulsation noise, Gaussian high-pass filter, GHPF, for removing the additive-periodical noise, and multi-scale morphological enhancement filter, MIF, for enhancement the low-contrast infrared image. An image enhancement filter, MIF, was developed based on white top-hat transformation and principle of magnifying image foreground. A squared-formed structuring element was used with a multi-scale side length ? having values ranging from the smallest detectable crack to the largest object. Gray-scale peaks, i.e. the foreground of the infrared image are multiplied by a factor, 1/?, for magnifying small object to a larger magnitude while the larger one to a moderate level.The main reason of horizontal stratified rock masses roadways failure are the sides of roadways horizontal stress release, vertical stress increased. The sides of roadway formed no lateral restraint of compression stress zone. This area of rock masses under the concentration stress produces plastic deformation, or rupture along the weak joint surface. Eventually caused stratified rock deformation and broken. Almost no cohesive force exists between broken rocks. The sides of roadway compressive stress area only need to overcome the friction between the layers, can cause sliding deformation of rock strata. During the initial loading phase the sides of roadway moved towards roadway cross section, but the roadway itself has not damage. The floor strata of the roadway under the effect of in parallel to the bedding direction compressive stress appear flexure deformation show as the floor heave. Horizontal stratified physical model rock masses of floor is mainly coal seam, the strength is relatively low, easily happened floor heave phenomenon. The roof of the roadway can be seen as a rock beam, and the ends of the beam under enormous extrusion. The main reason of rock beam failure is the huge horizontal stress, but not failure in the form as a beam under vertical stress. With the larger horizontal pressure, the tensile stress area almost disappears in the rock beam. So in the experiment the roof of roadway was not failure under the smaller tensile stress level.Horizontal stratified rock mass physical model roadway response analysis using the new infrared images was performed. Comparison to the previous processing of the same images in earlier work and to the photographs illustrates the significant improvement using sequence of the noise-reduction filters and image enhancement filter. The forewarnings on rock failure represented by the new image is accurate, and deeper understanding of the failure mechanisms on the simulated tunnel in horizontally bedded rock masses was achieved. Can be seen from the analysis of characteristics of infrared and strain analysis the stress increase will have obvious effects on surrounding rock of roadway. The strain change in the sides and floor of roadway are bigger than change in the roof. Shows coal seam in the sides and floor are greatly influenced by the stress change. Infrared image reveals under the influence of loading, exist strong static friction and dynamic friction between rock strata and the sliding friction is the main reason of roadway deformation and failure.The averaged infrared radiation temperature field, <IRT>, represents the overall energy release rate for the stressed rock masses. The <IRT> curve has a short linear phase during the first loading stage, and after that oscillates with different periods and amplitude, illustrating the stick-slip behavior of the steeply inclined rock masses under stressing. Overburden depth and loading speed have a significant impact on the evolution pattern of the <IRT> curve. Under small overburden depth and low loading speed, the <IRT> curve oscillates with longer period and small amplitude; whereas, under great overburden depth and fast loading speed, with shorter period and large amplitude.The anisotropic behavior of the strata is well represented by the infrared image sequence. At the initial loading, the infrared image has an infrared temperature distribution with a scattering-random manner, indicating the elastic and intact state. Anisotropy of the rock behavior was observed early in the first loading stage by the belt-like infrared temperature distribution. During the subsequent loading, at static friction corresponding to the stick phase in <IRT> curve, the intense static friction between the blocks within rock stratum and the interface static friction between the strata are represented by high and low large-scale infrared temperature distribution. At low-level loading, the coal seam is deformed firstly with intense internal friction corresponding to high infrared temperature belts; while the mudstone has little deformation corresponding to low infrared temperature belts. At high-level loading corresponding to the slip phase in <IRT> curve, the infrared temperature distribution pattern is inversed, i.e. low infrared temperature belt represents the coal seam and high infrared temperature represents the mudstone, indicating the loosening of the coal rock due to fracture and slippage. Convergence of the two-side walls, detachment of the immediate roof and floor heave is also well represented by the infrared temperature distribution in the infrared image sequence.Through the analysis of 45? strata infrared image we can see the loading rate to the destruction of the model has a certain influence. At low-level loading and small loading rate, the rock masses are given priority to with static friction. At high-level loading and fast loading rate, the rock masses main appear dynamic friction, fracture, interlayer sliding phenomenon. The Fourier spectra analysis of the image matrix showed that: in the stage of small loading rate, low amplitude and no dominant frequency of the major component represents the deformation of surrounding rock elastic stage, major component on the high frequency represents the rock mass damage, the extent of the damage is inversely proportional to the frequency; in the stage of fast loading rate, amplitude of the major component are significantly higher than the former, the major component with highest amplitude represents the most critical damage. Illustrate the Fourier spectra are more sensitive to the external load: in the sticking phase, is represented by the high-band and high amplitude precursor component; in the slipping phase, represented by high-amplitude and low-band components is the precursory components predicting the major imminent fracture event.Compared with the <IRT> curve and infrared image, the Fourier spectra of the image matrix are more sensitive to the external load. The load increase and the stress variation are well represented by the major components(i.e. periodic components) with their frequencies and amplitude. In the most of the loading stages in this experiment, the horizontal stress is higher than the vertical stress with the lateral pressure coefficient is larger than 1. Accordingly, the horizontal spectrum has more major components with higher amplitude, representing the anisotropy of the rock very well. The sticking phase, corresponding to the peaks in <IRT> curve, is represented by the high-band and high amplitude single component in the horizontal spectrum. The slipping phase, i.e. the troughs in <IRT> curve, is represented by high-amplitude and low-band components, i.e. the so-called “frequency shift”. These abnormal components could be precursory warning information for the imminent rock failure events.The spatial Fourier spectra, |F(u)| and |F(v)|, and spatial frequency, are employed to characterize the frequency-spectra features of the infrared image. The ultra-high spatial frequency component with large amplitude is a precursor for predicting the imminent dynamic interlayer slip or fracture, and for indicating the dynamic nature of an on-going event. The low spatial frequency component may be served as 1) a precursor of a tunnel wide scale event such as the interlayer slip if the amplitude was high, and 2) an indicator of the tunnel-wide sphere of influence that the stress redistribution extends if the amplitude was small or moderate.The processed infrared image best represents rock behavior by two major infrared temperature distribution patterns. For loading cases with low-level, the coal strata were over stressed indicated by high infrared temperature distribution while the mudstone strata were less stressed represented by low infrared temperature. For loading cases with high-level, the infrared temperature distribution is inversed, i.e. the mudstone strata were over stressed indicated by high infrared temperature while the coal strata were less stressed indicated by low infrared temperature. The first infrared temperature pattern indicates the static interlayer friction and the second one indicates the dynamic interlayer friction.Comparison of the rock behaviors exhibited by the two different inclined rock masses, increased knowledge was gained by observing the infrared images which depict the structural effects of the stratified rock masses: for the horizontal strata, the infrared temperature distribution on the infrared images is localized with a plastic manner; for 45? strata, the faulting-like and localized infrared temperature distribution were seen on the infrared images. Infrared image with high contrast belt reflects strata dip leads to unstable sliding friction damage in the 45? strata physical model. The infrared images elucidate visually the structural effect and demonstrate the excavation-induced damage mechanisms which are closely related to the dips of the stratified rock masses.In this paper, the infrared detection technology applied in large scale physical model experiment, solve the problem of the identification of a thermal elastic and thermoplastic. We obtained the horizontal stratified and 45? inclined stratified roadway deformation and failure characteristics under external load. Have great significance for mechanical behavior and failure mechanism of complex rock mass structure. Both field geological detection and laboratory large-scale physical model experiments of infrared image technology have broad application prospects. |
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