【摘要】：隨著我國地下巖土工程建設(shè)的快速發(fā)展,人們對爆破施工破巖技術(shù)提出了更高的要求:一方面,盡可能使能量沿預(yù)爆破方向釋放,提高有效爆炸破巖能量的利用率,另一方面,有效控制爆生裂紋的發(fā)展方向,減少爆破對保留巖體的損傷和破壞�；谶@兩個目的,人們提出了切槽炮孔爆破、聚能藥卷爆破等定向斷裂控制爆破技術(shù)。然而,由于天然巖體中廣泛分布著大量的節(jié)理、裂隙、孔洞等結(jié)構(gòu)面,對爆炸應(yīng)力波的傳播和爆生裂紋的擴(kuò)展都有顯著的影響,極大地影響了爆炸破巖的效果。尤其在節(jié)理發(fā)育的巖體中,往往很難形成較好的爆破輪廓。要解決這一問題,最基本地,就要首先弄清爆炸應(yīng)力波與含結(jié)構(gòu)面巖體的相互作用及爆生裂紋的擴(kuò)展特性。本文針對爆炸應(yīng)力波在含結(jié)構(gòu)面巖體中的波形轉(zhuǎn)換機(jī)制、誘生裂紋與巖體中結(jié)構(gòu)面的相互作用及其動態(tài)斷裂特性開展了理論分析、實(shí)驗(yàn)研究和數(shù)值模擬“三位一體”的研究,主要得到以下結(jié)論:基于應(yīng)力波理論,對P波和S波分別沿不同方向入射到動態(tài)裂紋時產(chǎn)生的反射波的反射系數(shù)進(jìn)行了理論求解。當(dāng)爆炸P波的傳播方向與動態(tài)裂紋的擴(kuò)展方向垂直時,在裂紋面處產(chǎn)生的反射拉伸P波與入射P波相互疊加,使垂直于裂紋面方向的應(yīng)力場表現(xiàn)為拉、壓交替的動態(tài)演化,動態(tài)裂紋呈“波浪式”向前擴(kuò)展的斷裂形態(tài)。當(dāng)P波傾斜入射到動態(tài)裂紋處時,裂紋附近的應(yīng)力場由純拉伸應(yīng)力場轉(zhuǎn)變?yōu)?拉剪/壓剪)復(fù)合應(yīng)力場,使裂紋朝向P波波源的方向擴(kuò)展。當(dāng)爆炸P波的傳播方向與運(yùn)動裂紋的擴(kuò)展方向相反時,裂紋面處只產(chǎn)生反射P波,此時,P波對裂紋尖端應(yīng)力場的影響等效于在裂紋尖端的應(yīng)力場中施加一個平行于裂紋面方向的應(yīng)力常量,對裂紋的擴(kuò)展角度和材料的斷裂韌性都有較大影響。爆炸P波和S波在結(jié)構(gòu)面處的相互轉(zhuǎn)換顯著改變了巖體介質(zhì)中的應(yīng)力場分布特征,進(jìn)而決定了巖體中動態(tài)裂紋產(chǎn)生的位置及其擴(kuò)展的方向。數(shù)值模擬了爆炸P波和S波分別與0°、45°和90°三種不同角度裂紋相互作用的動態(tài)過程,直觀顯示了P波和S波在遇到不同角度裂紋時的波形轉(zhuǎn)換過程,得到了裂紋尖端附近顆粒質(zhì)點(diǎn)的振動規(guī)律、試件內(nèi)部應(yīng)力場的分布特征及其誘生裂紋的斷裂模式。開展了含張開裂紋介質(zhì)分別在切槽炮孔爆破和普通炮孔爆破中爆生裂紋斷裂機(jī)理的實(shí)驗(yàn)室實(shí)驗(yàn)。爆生裂紋擴(kuò)展到垂直張開裂紋時,張開裂紋阻礙了裂紋的擴(kuò)展,并沿張開裂紋兩端產(chǎn)生新的翼裂紋,其擴(kuò)展方向與爆生裂紋的擴(kuò)展方向近似同向。結(jié)合數(shù)值模擬結(jié)果可知,爆炸應(yīng)力波在遇到張開裂紋后,張開裂紋阻隔了爆炸應(yīng)力波的傳播,并在張開裂紋端部發(fā)生衍射,產(chǎn)生應(yīng)力集中,誘導(dǎo)翼裂紋沿張開裂紋端部起裂。張開裂紋背面的應(yīng)力是爆炸應(yīng)力波在張開裂紋端部產(chǎn)生的衍射波繞射到張開裂紋背面引起的。與普通炮孔爆破相比,采用切槽炮孔爆破時,切槽方向爆生裂紋的起裂時間較非切槽方向早10ms,促使爆炸能量沿切槽方向優(yōu)先釋放;切槽爆破中翼裂紋起裂以Ⅰ型拉伸破壞為主,而普通炮孔爆破時翼裂紋起裂以Ⅱ型剪切破壞為主;切槽爆破中爆生翼裂紋的擴(kuò)展速度和裂紋尖端的應(yīng)力強(qiáng)度因子K_Ⅰ~d的衰減速率下降,較普通炮孔爆破時翼裂紋的擴(kuò)展時間和擴(kuò)展長度分別增加了22.7%和17.8%。實(shí)驗(yàn)分析了Ⅰ型動態(tài)裂紋與張開孔洞相互作用過程中裂紋的動態(tài)斷裂特性。當(dāng)Ⅰ型動態(tài)裂紋朝向鄰近孔洞擴(kuò)展時,孔洞對動態(tài)裂紋的擴(kuò)展速度和裂紋尖端的動態(tài)應(yīng)力強(qiáng)度因子有抑制作用,且孔洞直徑越大,抑制作用越強(qiáng);當(dāng)Ⅰ型動態(tài)裂紋與孔洞貫通后,孔洞的存在阻礙了動態(tài)裂紋的擴(kuò)展,表現(xiàn)為裂紋尖端被“鈍化”,裂紋的起裂韌度提高了9.58%~13.87%;裂紋由孔洞處再次起裂時的擴(kuò)展速度和動態(tài)應(yīng)力強(qiáng)度因子出現(xiàn)明顯的跳躍。裂紋斷裂面分析表明,裂紋與孔洞貫通前,斷裂面較為光滑,擴(kuò)展路徑平直;裂紋從孔洞處起裂后,斷裂面的粗糙程度顯著增加,擴(kuò)展路徑也更為彎曲。存在臨界孔洞直徑dc,使動態(tài)裂紋與臨界孔洞貫通后,孔洞吸收的彈性變形能最多,應(yīng)力集中程度最大,“鈍化效應(yīng)”最顯著。開展了閉合結(jié)構(gòu)面與動態(tài)裂紋相互作用的實(shí)驗(yàn)研究。結(jié)果表明由于應(yīng)力加載率和結(jié)構(gòu)面傾角的不同,動態(tài)裂紋與閉合結(jié)構(gòu)面相遇后,產(chǎn)生三種可能的擴(kuò)展形態(tài):(1)動態(tài)裂紋直接穿過弱面向基質(zhì)擴(kuò)展;(2)動態(tài)裂紋沿弱面擴(kuò)展;(3)動態(tài)裂紋沿弱面擴(kuò)展一段距離后再偏向基質(zhì)擴(kuò)展。在節(jié)理巖體爆破中,由于應(yīng)力加載率和結(jié)構(gòu)面傾角的變化,爆生裂紋遇到閉合結(jié)構(gòu)面后的擴(kuò)展形態(tài)在時間上的不斷演化和在空間上的不斷疊加共同構(gòu)成了節(jié)理巖體中密集的爆破裂隙。結(jié)合霍普金森桿實(shí)驗(yàn)系統(tǒng)和數(shù)字圖像相關(guān)法定量分析了動態(tài)應(yīng)力波強(qiáng)度、結(jié)構(gòu)面傾角及其強(qiáng)度對動態(tài)裂紋的影響;獲得了動態(tài)裂紋與結(jié)構(gòu)面相互作用過程中的位移場和應(yīng)變場隨時間的動態(tài)演化云圖。隨著應(yīng)力加載率的提高,動態(tài)裂紋在閉合結(jié)構(gòu)面中的擴(kuò)展速度增大,偏移距離下降,穿過弱面擴(kuò)展的裂紋數(shù)量不斷增多。隨著閉合結(jié)構(gòu)面傾角的增加,裂紋沿閉合結(jié)構(gòu)面擴(kuò)展的偏移距離呈非線性下降的特點(diǎn):當(dāng)閉合結(jié)構(gòu)面傾角在30°~60°之間時,動態(tài)裂紋的偏移距離基本保持不變,當(dāng)閉合結(jié)構(gòu)面傾角大于60°或小于30°時,動態(tài)裂紋的偏移距離隨結(jié)構(gòu)面傾角的增加呈線性下降的特點(diǎn)。當(dāng)結(jié)構(gòu)面的抗拉強(qiáng)度高于加載力沿結(jié)構(gòu)面方向的拉應(yīng)力時,裂紋沿結(jié)構(gòu)面的偏移距離受沿裂紋面方向的能量釋放率的控制;當(dāng)結(jié)構(gòu)面的抗拉強(qiáng)度不足以抵抗加載力沿結(jié)構(gòu)面方向的拉應(yīng)力時,裂紋沿結(jié)構(gòu)面的偏移距離受結(jié)構(gòu)面方向的拉應(yīng)力的控制。研究了應(yīng)力波作用下相向擴(kuò)展兩條裂紋的動態(tài)斷裂特性及其相互作用機(jī)理。焦散線實(shí)驗(yàn)結(jié)果表明相向擴(kuò)展兩條裂紋在擴(kuò)展過程中呈“同性(裂紋尖端與裂紋尖端)相斥,異性(裂紋尖端與裂紋面)相吸”的特點(diǎn)。結(jié)合動光彈性實(shí)驗(yàn)和數(shù)值模擬結(jié)果可知,相向擴(kuò)展的兩條裂紋在相互作用的過程中,平行于裂紋面方向的應(yīng)力常數(shù)項(xiàng)(T應(yīng)力)顯著增大,改變了裂紋的擴(kuò)展角度、擴(kuò)展速度、材料的斷裂韌度。當(dāng)T應(yīng)力為負(fù)時,裂紋的擴(kuò)展角度減小,裂紋沿豎直方向的擴(kuò)展距離減少;反之,正的T應(yīng)力,對裂紋擴(kuò)展角度有促進(jìn)作用,增大裂紋擴(kuò)展的豎向距離。在分析多裂紋相互作用時,應(yīng)采用三參數(shù)(K_Ⅰ、K_Ⅱ和T應(yīng)力)來確定裂紋的擴(kuò)展角度、擴(kuò)展距離等斷裂參數(shù)。在實(shí)際工程中,通過改變爆破介質(zhì)的受力,增加負(fù)的T應(yīng)力,有助于控制裂紋的走向,實(shí)現(xiàn)精細(xì)爆破施工;相反,若增加正的T應(yīng)力,則有利于增大爆破破巖的范圍,提高松動爆破的效果。數(shù)值分析了主應(yīng)力比值、裂紋豎向間距和材料力學(xué)特性對相向擴(kuò)展裂紋斷裂行為的影響。當(dāng)兩裂紋尖端相距較大時,隨著遠(yuǎn)場主應(yīng)力比值的增大,裂紋尖端的Tresca應(yīng)力由對稱的蝴蝶狀向扁平狀發(fā)展,擴(kuò)大了多裂紋相互影響的作用區(qū)域。當(dāng)兩裂紋尖端水平間距較小時,主應(yīng)力比值的改變對裂紋尖端的應(yīng)力場參數(shù)(K_Ⅰ、K_Ⅱ和T應(yīng)力)和裂紋擴(kuò)展軌跡影響較小。裂紋偏離初始方向擴(kuò)展的最大豎向距離隨裂紋初始豎向間距的增加呈非線性下降的特點(diǎn)。存在臨界初始豎向間距S_c,當(dāng)兩條裂紋的初始豎向距離S小于臨界豎向間距S_c時,裂紋沿豎直方向的最大偏移距離W_(max)基本穩(wěn)定。當(dāng)S大于S_c時,W_(max)隨S的增大呈線性降低的趨勢。隨著材料彈性模量的增大,泊松比的減小,材料的臨界豎向間距S_c下降。對于大理巖、花崗巖和有機(jī)玻璃三種材料而言,在相同的初始豎向間距下,相向擴(kuò)展裂紋的擴(kuò)展軌跡相互影響的顯著程度依次是:大理巖花崗巖有機(jī)玻璃。結(jié)合T應(yīng)力理論,分析了爆炸應(yīng)力波與爆生裂紋的相互作用機(jī)理。當(dāng)爆生裂紋的擴(kuò)展方向與爆炸P波的傳播方向相反時,爆炸P波對爆生裂紋的作用等效于在裂紋尖端施加負(fù)的T應(yīng)力,增大了材料的斷裂韌度,阻礙了裂紋的擴(kuò)展,使裂紋的擴(kuò)展速度急劇下降。反之,當(dāng)爆生裂紋的擴(kuò)展方向與爆炸P波的傳播方向同向時,材料的斷裂韌度下降,擴(kuò)展速度上升。從實(shí)驗(yàn)的角度看,S波與裂紋的相互作用可使裂紋的擴(kuò)展速度下降,顯著改變了裂紋的擴(kuò)展方向。
[Abstract]:With the rapid development of underground geotechnical engineering construction in our country, people put forward higher requirements for rock breaking technology in blasting construction: on the one hand, as far as possible to release energy along the direction of pre-blasting, improve the utilization rate of effective blasting rock breaking energy, on the other hand, effectively control the development direction of blasting cracks, reduce blasting damage to retained rock mass and Destruction. For these two purposes, directional fracture controlled blasting techniques such as notched blasting and shaped charge blasting have been proposed. However, a large number of joints, cracks, holes and other structural planes are widely distributed in natural rock mass, which have a significant impact on the propagation of explosive stress waves and the propagation of explosive cracks, greatly affecting the explosion. It is difficult to form a good blasting profile, especially in jointed rock mass. To solve this problem, the interaction between explosive stress wave and rock mass with structural plane and the propagation characteristics of explosive cracks must be clarified firstly. The interaction between induced cracks and structural planes in rock mass and their dynamic fracture characteristics are analyzed theoretically. The experimental study and numerical simulation of "trinity" are carried out. The main conclusions are as follows: Based on the stress wave theory, the reflection coefficients of P wave and S wave incident to dynamic cracks in different directions are calculated. When the propagation direction of explosive P-wave is perpendicular to the propagation direction of dynamic crack, the reflected tensile P-wave and incident P-wave are superimposed on the crack surface, so that the stress field perpendicular to the crack surface exhibits the dynamic evolution of tension and compression alternately, and the dynamic crack exhibits the fracture pattern of "wave-like" propagation forward. The stress field near the crack changes from pure tensile stress field to (tension-shear/compression-shear) composite stress field, which makes the crack propagate toward P-wave source. When the propagation direction of explosive P-wave is opposite to the propagation direction of moving crack, only reflective P-wave is produced at the crack surface, and then the effect of P-wave on the stress field near the crack tip is also discussed. When a stress constant parallel to the crack plane is applied to the stress field at the crack tip, both the crack propagation angle and the fracture toughness of the material are greatly affected. The dynamic process of explosive P-wave and S-wave interacting with cracks at different angles of 0, 45 and 90 was simulated. The waveform transformation process of P-wave and S-wave when they encounter cracks at different angles was visualized. The vibration law of particle near the crack tip and the stress field in the specimen were obtained. The distribution characteristics and fracture mode of cracks induced by cracks are studied. Laboratory experiments are carried out on the fracture mechanism of explosive cracks in notched blasthole blasting and ordinary blasthole blasting respectively. The propagation direction of explosive stress wave is approximately the same as that of explosive crack. According to the numerical simulation results, the propagation of explosive stress wave is blocked by the tensile crack, and diffraction occurs at the end of the tensile crack, which results in stress concentration and induces the crack initiation along the end of the tensile crack. The diffraction wave produced by the explosive stress wave at the end of the tensile crack is diffracted to the back of the tensile crack. Compared with the ordinary blasting, the initiation time of the explosive crack in the notched direction is 10 ms earlier than that in the non-notched direction when the notched blasting is used, which makes the explosive energy release preferentially along the notched direction. Tensile failure is dominant, while type II shear failure is dominant for wing crack initiation in ordinary blasting. The propagation velocity of wing crack and the attenuation rate of stress intensity factor K_ I~d at crack tip in notched blasting decrease, and the propagation time and length of wing crack increase by 22.7% and 17.8% respectively. The dynamic fracture characteristics of crack in the interaction between mode I dynamic crack and open hole are analyzed. The crack initiation toughness increases by 9.58%~13.87%. The crack propagation velocity and dynamic stress intensity factor appear obvious jump when the crack starts again from the hole. The analysis of crack fracture surface shows that the crack tip is "passivated" and the crack initiation toughness increases by 9.58%~13.87%. It is smooth and the propagation path is straight; the roughness of fracture surface increases significantly and the propagation path is more curved after the crack initiation from the hole. There is a critical hole diameter dc, which makes the elastic deformation energy absorbed by the dynamic crack and the critical hole pass through, and the stress concentration is the greatest, and the "passivation effect" is the most significant. The results show that there are three possible propagation modes after the dynamic crack meets the closed structural plane due to the difference of stress loading rate and inclination angle of the structural plane: (1) the dynamic crack propagates directly through the weak face to the matrix; (2) the dynamic crack propagates along the weak face; (3) the dynamic crack propagates along the weak face. In the blasting of jointed rock mass, due to the change of stress loading rate and dip angle of structural plane, the continuous evolution of blasting crack propagation form after encountering closed structural plane in time and the continuous superposition in space constitute a dense blasting crack in jointed rock mass. The influence of dynamic stress wave intensity, dip angle and strength of structural plane on dynamic crack is analyzed quantitatively by system and digital image correlation method. With the increase of the inclination angle of the closed structure plane, the offset distance of the crack propagating along the closed structure plane decreases nonlinearly. When the inclination angle of the closed structure plane is between 30 and 60 degrees, the offset distance of the dynamic crack remains basically unchanged, while that of the closed structure is between 30 and 60 degrees. When the inclination angle is greater than 60 degrees or less than 30 degrees, the offset distance of dynamic crack decreases linearly with the increase of the inclination angle of structural plane. The displacement distance of cracks along the structural plane is controlled by the tensile stress along the structural plane when the degree of stress is not enough to resist the tensile stress along the structural plane. The results of dynamic photoelasticity experiment and numerical simulation show that the stress constant term (T stress) parallel to the direction of the crack surface increases remarkably during the interaction between the two cracks, and the crack propagation is changed. When the T stress is negative, the propagation angle of the crack decreases and the propagation distance along the vertical direction decreases; on the contrary, the positive T stress promotes the propagation angle of the crack and increases the vertical distance of the crack propagation. In practical engineering, by changing the force of blasting medium and increasing negative T stress, it is helpful to control the direction of crack and realize fine blasting construction; on the contrary, if the positive T stress is increased, it is helpful to enlarge the range of blasting rock breaking and improve the effect of loose blasting. The effects of principal stress ratio, crack vertical spacing and material mechanical properties on the fracture behavior of a phase-propagating crack are investigated. When the two crack tips are separated greatly, the Tresca stress at the crack tip develops from a symmetrical butterfly to a flat shape with the increase of the far-field principal stress ratio, and the interaction region of multiple cracks is enlarged. When the horizontal spacing between crack tips is small, the change of the ratio of principal stress has little effect on the stress field parameters (K_I, K_II and T stress) and crack propagation trajectory. When the initial vertical distance S is less than the critical vertical distance S_c, the maximum deviation W_ (max) along the vertical direction of the crack is basically stable. When S is greater than S_c, W_ (max) decreases linearly with the increase of S. With the increase of elastic modulus, the Poisson's ratio decreases and the critical vertical distance S_c decreases. With the same initial vertical spacing between rock and plexiglass, the significant degree of the interaction between the propagation trajectories of phase-propagating cracks is: marble granite plexiglass. Combining with T-stress theory, the interaction mechanism between explosive stress wave and explosive crack is analyzed. When the propagation direction of explosive P-wave is opposite, the effect of explosive P-wave on explosive crack is equivalent to applying negative T-stress at the crack tip, which increases the fracture toughness of material, hinders the propagation of crack, and makes the propagation speed of crack decrease sharply. From the experimental point of view, the interaction between S wave and crack can decrease the crack propagation velocity and change the crack propagation direction significantly.
【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】：TU45
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本文編號：2180226