本文選題：回采擾動 + 裂隙實測�。� 參考：《中國礦業(yè)大學(xué)(北京)》2017年博士論文

【摘要】：本論文的研究依托于國家自然科學(xué)基金面上項目(51374216)。瓦斯治理最重要的方法就是瓦斯抽采,而瓦斯抽采最關(guān)鍵的問題就是合理抽采參數(shù)的確定。工作面回采過程頂板的裂隙場是采空區(qū)瓦斯運移的主要通道,而回采過程又導(dǎo)致頂板裂隙場一直處于動態(tài)的變化置中,因此對工作面回采影響下頂板裂隙場的演化規(guī)律研究就十分重要,是確定頂板瓦斯抽放鉆孔與高位瓦斯抽放巷道等手段布置方式的主要依據(jù)。本文以工作面頂板圍巖在采動影響下的裂隙場演化規(guī)律為研究方向,通過實驗室力學(xué)實驗、分析宏細(xì)觀裂隙分布、現(xiàn)場鉆孔窺視觀測、頂板裂隙三維網(wǎng)絡(luò)重構(gòu)、真實地質(zhì)參數(shù)條件下數(shù)值模擬等研究方法,重點研究了受工作面采動應(yīng)力影響下,工作面頂板圍巖內(nèi)的裂隙場演化規(guī)律。通過研究,本文主要得到了如下結(jié)論:(1)采用了最大應(yīng)力逐漸升高的應(yīng)力路徑下的巖石循環(huán)加卸載實驗方案,該方案的應(yīng)力加卸載速度依據(jù)現(xiàn)場頂板受力特征確定,同時對實驗過程巖石聲發(fā)射進(jìn)行監(jiān)測。發(fā)現(xiàn)巖石的循環(huán)加卸載實驗可以根據(jù)聲發(fā)射信號的特征分為三個階段,分別是聲發(fā)射偶發(fā)階段、發(fā)展階段與高峰階段。以聲發(fā)射事件數(shù)率突然升高為標(biāo)志的高峰階段是最主要的階段,一般始于峰值強度的60%~70%左右。在高峰階段,高振幅信號出現(xiàn)更多,且聲發(fā)射定位也明顯集中,集中區(qū)域與最終的樣品破壞位置相對應(yīng)。巖石整個加載過程90%以上的聲發(fā)射事件都集中在這個階段,可以認(rèn)為巖石內(nèi)部的裂紋、孔隙等各類損傷都主要是在這個階段產(chǎn)生的,因此這也是巖石破壞的最主要階段。(2)聲發(fā)射信號有明顯的Kaiser效應(yīng)和Felicity效應(yīng),通過對Felicity比進(jìn)行計算,發(fā)現(xiàn)Kaiser效應(yīng)的準(zhǔn)確性隨著循環(huán)加卸載的過程而逐漸降低,聲發(fā)射越來越多地發(fā)生于Kaiser點之前。在對后幾個循環(huán)的卸載階段聲發(fā)射信號進(jìn)行詳細(xì)觀察后發(fā)現(xiàn),當(dāng)應(yīng)力小于上循環(huán)的最大值后,會產(chǎn)生明顯的聲發(fā)射信號,但振幅和事件數(shù)率都小于本循環(huán)加載階段。經(jīng)分析,認(rèn)為當(dāng)應(yīng)力小于上循環(huán)最大之后,巖石內(nèi)部產(chǎn)生了一定程度的塑性恢復(fù)而產(chǎn)生了聲發(fā)射信號;而在下一循環(huán)的加載階段,這些塑性恢復(fù)在達(dá)到本循環(huán)最大應(yīng)力之前就又被破壞而產(chǎn)生聲發(fā)射信號,表現(xiàn)出了Felicity效應(yīng),這個假設(shè)很好的解釋了Felicity效應(yīng)產(chǎn)生的原因。由于該現(xiàn)象也是在上一循環(huán)應(yīng)力最大值之后產(chǎn)生,因此定義為后Kaiser效應(yīng)。(3)在細(xì)觀尺度上,聲發(fā)射信號能量與釋放的彈性能相關(guān),進(jìn)而與產(chǎn)生裂隙所需消耗的總能量相關(guān),進(jìn)而與裂隙的面積相關(guān)。根據(jù)聲發(fā)射能量分布可以推斷,巖石在破壞過程中,首先是大量小規(guī)模裂隙隨機出現(xiàn);隨著小裂隙在數(shù)量上的增加,它們之間相互連接、貫通,同時產(chǎn)生較大能量的聲發(fā)射信號;隨著裂隙進(jìn)一步擴展,最終貫穿巖石,導(dǎo)致巖石的破壞,并在這個過程產(chǎn)生大能量的聲發(fā)射。在宏觀尺度上,根據(jù)裂隙面大小分布可以進(jìn)行類似的巖體內(nèi)的裂隙場演化分析。(4)在細(xì)觀尺度分析了巖石受載過程的彈性階段的平衡方程、幾何方程、變形控制方程、本構(gòu)方程等,歸納了以破壞面積占比、摩爾庫倫強度準(zhǔn)則與抗拉強度準(zhǔn)則、聲發(fā)射累積振鈴計數(shù)等不同參數(shù)為依據(jù)的損傷變量定義,最后結(jié)合上一章巖石循環(huán)加卸載條件下的聲發(fā)射能量累積的特征,定義了以聲發(fā)射累積能量為參數(shù)的損傷變量D,能夠更好的反映巖石在不同時刻的損傷規(guī)模。(5)在細(xì)觀尺度上,對聲發(fā)射不同振幅值對應(yīng)的事件總數(shù)、和不同能量對應(yīng)的事件總數(shù)之間的關(guān)系進(jìn)行分析,發(fā)現(xiàn)小振幅、小能量聲發(fā)射事件占據(jù)絕對的主導(dǎo),兩者呈現(xiàn)為=(6-(7形式的冪函數(shù);在宏觀尺度上,對現(xiàn)場地質(zhì)體宏觀裂隙面的尺寸進(jìn)行統(tǒng)計,發(fā)現(xiàn)其在某個尺寸所對應(yīng)的裂隙面數(shù)量之間,在對數(shù)圖上為一條直線,擬合規(guī)律也呈現(xiàn)負(fù)冪數(shù)關(guān)系,與細(xì)觀尺度巖石聲發(fā)射振幅、能量分布規(guī)律一致,可以認(rèn)為巖石在細(xì)觀上的損傷與宏觀上的裂隙破壞有一致性,同時驗證了巖石材料的自相似性與分形特性。(6)在宏觀尺度,分析了前視鉆孔窺視儀的工作原理,提出了前視鉆孔窺視視頻轉(zhuǎn)換為鉆孔全景圖片的方法,以及從中提取鉆孔裂隙產(chǎn)狀、位置等信息的原理。利用提出的轉(zhuǎn)換方法將現(xiàn)場的鉆孔窺視視頻轉(zhuǎn)換為鉆孔全景圖片,并對圖片中的裂隙信息進(jìn)行提取。進(jìn)一步地,從這些裂隙信息中提取了裂隙場三維重構(gòu)模擬所需要的裂隙組強度、產(chǎn)狀、大小等參數(shù)。(7)利用裂隙的相關(guān)參數(shù),基于不連續(xù)面三維網(wǎng)絡(luò)重構(gòu)原理,使用MoFrac軟件,進(jìn)行了基于現(xiàn)場鉆孔觀測基礎(chǔ)上的工作面頂板裂隙場時空演化三維模擬,并得到以下規(guī)律:(1)從空間位置分析,在沿工作面推進(jìn)方向,裂隙的分布空間主要位于采空區(qū)上方范圍;在沿工作面走向方向,回采25m及之前,裂隙主要集中在與巷道距離60m范圍內(nèi),回采達(dá)到并超過50m后,在走向方向就變得更平均了;在高度方向,回采6m時裂隙分布在高度10m的范圍內(nèi),隨著工作面的推進(jìn),裂隙在高度范圍的分布越來越大,例如回采25m時高度在15m左右,回采75m和100m時達(dá)到了35m左右,本次現(xiàn)場觀測最高距離僅有35m,因此認(rèn)為裂隙場的真實分布要超過35m;(2)工作面回采6m時,產(chǎn)生的頂板裂隙大小普遍偏小,而隨著工作面的回采,頂板內(nèi)的裂隙面積逐漸增大,老頂?shù)某醮闻c周期來壓導(dǎo)致的特大裂隙面會進(jìn)一步切割、連通之前產(chǎn)生的中、小裂隙面,進(jìn)而生成復(fù)雜的、相互連通的裂隙網(wǎng)絡(luò),成為采空區(qū)頂板內(nèi)主要的瓦斯?jié)B流通道;(3)頂板內(nèi)產(chǎn)生的裂隙的傾角主要以水平方向為主,而裂隙的傾向則沒有太明顯的特征;關(guān)于裂隙面的密度,可以看出也是隨著工作面的回采而逐漸增大,并在50m之后逐漸穩(wěn)定。(8)本構(gòu)模型的選擇與材料參數(shù)的賦值在數(shù)值模擬中非常重要,是決定數(shù)值模擬結(jié)果是否合理的關(guān)鍵因素。在FLAC3D中考慮殘余強度,將模型的煤、巖體都定義為更加符合實際情況的應(yīng)變軟化模型,同時依據(jù)碎漲系數(shù)等參數(shù)確定了采空區(qū)范圍,并將采空區(qū)定義為雙屈服模型;另外,按照Weibull分布對煤層上覆54m頂板巖層的體積模量K和剪切模量G進(jìn)行隨機賦值。(9)通過對回采過程圍巖內(nèi)的垂直應(yīng)力與塑性破壞區(qū)演化進(jìn)行分析,得出:工作面前方12~14m范圍內(nèi)煤體處于塑性破壞;頂板內(nèi)的塑性破壞最開始主要出現(xiàn)在采空區(qū)上方,回采超過30m后開始在工作面前方煤巖體頂板內(nèi)產(chǎn)生;工作面回采至72m后再推進(jìn),采空區(qū)上方出現(xiàn)了一層平面的塑性破壞區(qū)域,這是穩(wěn)定的裂隙帶最下層,同時工作面正上方靠前的位置產(chǎn)生大量的塑性破壞,這與頂板的大范圍來壓或破壞有關(guān),內(nèi)部可能生成大量的裂隙。頂板的塑性破壞范圍可以反映頂板內(nèi)的裂隙面產(chǎn)生與演化,經(jīng)過對比與現(xiàn)場觀測結(jié)果吻合度較高。(10)提出了通過現(xiàn)場頂板鉆孔窺視觀測來獲得頂板裂隙場演化規(guī)律,進(jìn)而確定工作面頂板高效瓦斯鉆孔抽采技術(shù)關(guān)鍵參數(shù)的方法。結(jié)合頂板裂隙場的多孔介質(zhì)特征與瓦斯的主要來源分類,分析了頂板裂隙場的瓦斯?jié)B流規(guī)律,進(jìn)一步結(jié)合頂板垮落帶與裂隙帶高度公式,分析了現(xiàn)場工作面頂板瓦斯抽放鉆孔的布置主要參數(shù)�？紤]鉆孔有效抽放長度情況下,對N3-7工作面的鉆孔布置方案進(jìn)行了優(yōu)化,分別確定了進(jìn)風(fēng)巷高位鉆孔的布置方案,以及回風(fēng)巷鉆孔組的布置方案。該方案可以為N3-7工作面及其周圍的工作面的頂板瓦斯抽放鉆孔布置提供參考。
[Abstract]:The research of this paper is based on the project of National Natural Science Foundation (51374216). The most important method of gas control is gas extraction, and the most important problem of gas extraction is the determination of reasonable extraction parameters. The fracture field at the roof of the working face is the main channel of gas migration in the goaf, and the recovery process leads to the roof. The fracture field is always in the dynamic change, so it is very important to study the evolution law of the roof fissure field under the influence of the working face recovery. It is the main basis for determining the layout mode of the roof gas drainage drilling and the high gas drainage tunnel. For the research direction, through the laboratory mechanics experiment, we analyze the distribution of macro and micro cracks, the field borehole peep observation, the three-dimensional network reconstruction of the roof fissures, the numerical simulation of the real geological parameters and other research methods, focusing on the evolution law of the fracture field in the wall rock of the working face under the influence of the working face's mining stress. The main conclusions are as follows: (1) the experimental scheme of rock cyclic loading and unloading under the stress path of the maximum stress is adopted. The stress loading and unloading velocity of the scheme is determined by the stress characteristics of the site roof, and the acoustic emission of the rock is monitored at the same time. The cyclic loading and unloading experiments of the present rock can be based on the acoustic emission. The characteristics of the signal are divided into three stages, which are the occasional phase of acoustic emission, the development stage and the peak stage. The peak stage marked by the sudden rise of the number of acoustic emission events is the most important stage, which usually begins at about 60%~70% of the peak intensity. At the peak stage, the high amplitude signal appears more, and the acoustic emission location is also concentrated obviously. The middle area is corresponding to the final damage position of the sample. The acoustic emission events above 90% of the whole rock loading process are concentrated at this stage. It is considered that all kinds of cracks, such as cracks and pores in the rock are mainly produced at this stage, so this is the most important stage of rock failure. (2) the acoustic emission signals have obvious Kaiser Effect and Felicity effect, by calculating the Felicity ratio, it is found that the accuracy of the Kaiser effect gradually decreases with the process of cyclic loading and unloading, and the acoustic emission is more and more occurring before the Kaiser point. After the detailed observation of the acoustic emission signals at the unloading stage of the later cycles, the stress is less than the maximum value of the upper cycle. After that, the amplitude and the number of events are less than the cyclic loading stage. After analysis, it is believed that when the stress is less than the maximum cycle, the interior of the rock produces a certain degree of plastic recovery and produces the acoustic emission signal, and the plastic recovery is the largest in the next cycle. The acoustic emission signal is produced before the stress is destroyed again, showing the Felicity effect. This hypothesis is a good explanation of the cause of the Felicity effect. Since this phenomenon is also produced after the maximum value of the last cycle stress, it is defined as the post Kaiser effect. (3) on the meso scale, the energy of acoustic emission signal and the elastic energy released by the acoustic emission signal. The correlation is related to the total energy consumed by the crevice, which is related to the area of the fissure. According to the distribution of the acoustic emission energy, it is inferred that in the course of the rock failure, the first is a large number of small fractures randomly appearing. With the increase in the number of small fissures, they are connected and connected, and the sound of larger energy is produced. With the further expansion of the crack, the rock eventually runs through the rock, causing rock destruction and producing large energy acoustic emission in this process. On the macro scale, the fracture field evolution in similar rock mass can be carried out in the same rock mass according to the size distribution of the fracture surface. (4) the equilibrium of the elastic phase of the rock loading process is analyzed in the meso scale. The equation, geometric equation, deformation control equation, constitutive equation, etc. are defined by the definition of damage variables based on different parameters such as damage area occupation ratio, mole Kulun strength criterion and tensile strength criterion, acoustic emission accumulative ringing count and so on. Finally, the characteristics of acoustic emission energy accumulation under the conditions of rock cyclic loading and unloading in the last chapter are defined. The damage variable D with the parameters of the acoustic emission accumulated energy can better reflect the damage scale of the rock at different times. (5) on the meso scale, the total number of events corresponding to the different amplitude values of acoustic emission and the relationship between the total number of events corresponding to different energy are analyzed, and the small amplitude and small energy acoustic emission events are found to be absolute. Leading, the two are presented as = (6- (7 form) power function; on the macroscopic scale, the size of the macroscopic fissure surface of the field geological body is counted, and it is found that it is a straight line between the number of fracture surfaces corresponding to a certain size, and the logarithmic diagram is a negative power relation, the amplitude of the acoustic emission from the meso scale, the energy distribution gauge. According to the law, it can be considered that the damage of the rock in the mesoscopic damage is consistent with the fracture failure in the macro. At the same time, the self similarity and fractal characteristics of the rock material are verified. (6) the working principle of the forward borehole peep is analyzed on the macroscopic scale, and the method of converting the visual frequency of the forward borehole to the borehole panoramic image is put forward and it is proposed from it. Using the proposed transformation method, the borehole peep video is converted into a borehole panoramic picture by using the proposed transformation method, and the fracture information in the picture is extracted. Further, the parameters of the fracture group strength, shape, size and so on are extracted from these fissure information. (7) using the related parameters of the fissure, based on the three-dimensional network reconstruction principle of discontinuities, using the MoFrac software, the three-dimensional simulation of the space-time evolution of the roof crack field on the working face based on the field borehole observation is carried out, and the following rules are obtained: (1) the spatial position analysis, the direction along the working face, the distribution space of the fissure is mainly located in the mining. In the direction of the air area, in the direction of the face along the face, the crack is mainly concentrated in the range of 60m in the range of distance from the roadway. After the recovery reaches and exceeds the 50m, the direction becomes more average in the direction. In the high direction, the crack is distributed in the range of high 10m when the 6m is mined, and the fracture is distributed in the height range with the advancing of the working face. It is getting bigger and bigger, for example, the height of 25m is about 15m, and 75m and 100m have reached about 35m. The maximum distance of the field observation is only 35m. Therefore, the true distribution of the crack field is more than 35m; (2) the size of the roof crack is generally small when the face is recovered to 6m, and the area of the crack in the roof is gradual with the mining of the working face. In addition, the large fissure surface caused by the initial and periodic pressure of the old top will further cut, and the small fissure surface which is generated before connecting, then generates complex and interconnected fracture networks, and becomes the main gas seepage channel in the roof of the goaf, and (3) the inclination of the fissure produced in the roof is mainly in the horizontal direction and the fracture is tilted. There is no obvious characteristic in direction; on the density of the fracture surface, it can be seen that it is gradually increasing with the recovery of the working face, and gradually stabilizes after 50m. (8) the selection of the constitutive model and the assignment of material parameters are very important in the numerical simulation, which is the key factor determining the rationality of the numerical simulation results. In the case of FLAC3D, the residue is considered to be residual. In addition, the coal and rock mass of the model are defined as the strain softening model which is more consistent with the actual situation. At the same time, the goaf range is determined according to the parameters such as the coefficient of fragmentation. The goaf is defined as a double yield model. In addition, the volume modulus K and the shear modulus G of the overlying 54m top slate are randomly assigned according to the Weibull distribution. (9) Through the analysis of the vertical stress in the surrounding rock and the evolution of the plastic failure zone in the surrounding rock, it is concluded that the coal body is in plastic damage in the range of 12~14m in front of the work, and the plastic failure in the roof is mostly above the goaf. After the recovery exceeds 30m, the roof of the coal rock mass is produced in front of the working face, and the working face is recovered to 72m. In addition, a plastic failure area of the plane appears above the goaf, which is the lower layer of the stable fracture zone, and a large number of plastic damage is produced at the top of the working face, which is related to the large pressure or failure of the roof. The interior of the roof may produce a large number of cracks. The plastic failure range of the roof can reflect the roof. The formation and evolution of the fracture surface are in good agreement with the field observation results. (10) the evolution law of the roof fissure field is obtained through the field roof drilling peep observation, and then the key parameters of the high efficient gas drilling technology are determined. The porous media characteristics of the joint roof fracture field and the main gas are main. According to the classification of the source, the gas seepage law of the roof fissures field is analyzed, and the main parameters of the gas drainage drilling in the roof are analyzed by combining the height formula of the roof caving zone and the fracture zone. Considering the effective drainage length of the drilling hole, the drilling layout scheme of the N3-7 working face is optimized. The layout of the high hole drilling in the wind tunnel and the layout of the drilling group in the return air lane can provide reference for the layout of the roof of the working face of the N3-7 and the roof of the working face.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)(北京)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TD712.61;TD31

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