【摘要】：近年來,隨著我國經(jīng)濟建設的持續(xù)發(fā)展,地下巖土工程的規(guī)模不斷擴大,各種復雜的巖體力學問題越來越受到重視。許多大型結構工程的失穩(wěn)破壞都與爆炸、沖擊等動荷,載密切相關,如礦山開采、隧道爆破等。巖石是一種典型的準脆性材料,具有顯著的非均勻性,當動荷載達到巖石的強度極限時,能量會瞬間釋放并引發(fā)應力重分布,使局部力學性質迅速劣化,裂隙高速擴展,工程中如處理不當將可能引起重大工程事故并造成巨大的經(jīng)濟損失。因此,研究動荷載作用下巖體裂隙的擴展具有重要的理論價值和實踐意義。本文采用巖石動態(tài)過程破裂分析系統(tǒng)RPPA-dynamic,通過建立數(shù)值模型,對巖體在動荷載作用下裂紋擴展機制進行數(shù)值模擬研究。具體內容包括以下幾個方面：1.通過閱讀相關文獻,歸納、概括了國內外學者對于動荷載作用下巖體的破壞形式與裂隙擴展在理論、物理試驗和數(shù)值模擬等方面的研究現(xiàn)狀。2.建立地應力作用下巖體受到爆炸作用的二維數(shù)值模型,模擬了巖體在爆破荷載作用下裂紋萌生、擴展、貫通破壞的過程。討論了爆破應力波峰值強度、應力比和圍壓值大小對巖體破壞形式和裂紋擴展規(guī)律的影響。研究結果表明：(1)隨著K值由0、0.25、0.5、0.75逐漸增大,巖體的破壞模式是近似的,最終都是形成與最大壓應力方向一致的兩條豎直方向的主裂紋,但是裂紋最終長度逐漸減小,說明應力比越大,巖體越不容易發(fā)生破壞。(2)爆炸應力波峰值對裂紋擴展有重要影響,峰值越大,裂紋擴展能力越強。(3)當應力比K=1時,孔洞周圍出現(xiàn)四條互相垂直的主裂紋,且隨著圍壓值不斷增大,巖體內初始應力場改變,破壞由拉剪破壞轉變?yōu)榧羝茐臑橹?最終裂紋長度逐漸減小,圍壓大小對爆破裂紋擴展能力有明顯的抑制作用。3.建立含單條預制裂隙巖石試樣的數(shù)值模型,模擬了在動荷載作用下巖石試樣中預制的單條裂隙擴展過程,研究了應力波波長、峰值以及預制裂紋傾角對裂紋擴展方式的影響,并討論了動力與靜力作用下的裂隙擴展差異。研究結果表明：(1)當應力波波長相對很短時,在平行于預制裂紋上方萌生新的裂紋,長度與預制裂紋一致；當應力波波長逐漸增大,在預制裂紋兩尖端產(chǎn)生垂直于預制裂紋的翼裂紋并逐漸向巖石試樣上下兩端發(fā)展；當應力波波長增大到一定程度,巖石試樣的破壞模式與靜荷載作用下頗為接近。(2)巖石試樣的破壞程度隨著應力波峰值的增大而增大。(3)預制裂隙角度越大,巖體越不容易發(fā)生破壞,巖體強度呈現(xiàn)逐漸提高。(4)當應力波很短時,裂紋擴展方式主要由應力波波長控制,預制裂紋傾角的影響不明顯。(5)動、靜荷載作用下,巖石試樣的破壞模式有很大區(qū)別。應力波在平行于節(jié)理面迎波面方向產(chǎn)生反射拉伸波,出現(xiàn)層裂現(xiàn)象,而靜力條件下更容易出現(xiàn)翼型裂紋。
[Abstract]:In recent years, with the sustainable development of economic construction in China, the scale of underground geotechnical engineering continues to expand, and a variety of complex rock mechanics problems have been paid more and more attention. The instability and failure of many large-scale structural projects are closely related to explosion, impact and other dynamic loads, such as mining, tunnel blasting and so on. Rock is a typical quasi-brittle material, which has remarkable inhomogeneity. When the dynamic load reaches the strength limit of rock, the energy will release and cause stress redistribution, which makes the local mechanical properties deteriorate rapidly and the cracks expand at high speed. If handled improperly in the project, it may cause major engineering accidents and cause huge economic losses. Therefore, it is of great theoretical value and practical significance to study the expansion of rock mass cracks under dynamic load. In this paper, the rock dynamic process fracture analysis system RPPA-dynamic, is used to simulate the crack propagation mechanism of rock mass under dynamic load by establishing a numerical model. The specific contents include the following aspects: 1. By reading the relevant literature, this paper summarizes the research status of failure forms and fracture propagation of rock mass under dynamic load in theory, physical test and numerical simulation. 2. A two-dimensional numerical model of rock mass subjected to explosion under ground stress is established, and the process of crack initiation, propagation and penetration failure of rock mass under blasting load is simulated. The effects of blasting stress wave peak strength, stress ratio and confining pressure on the failure form and crack propagation of rock mass are discussed. The results show that: (1) with the increase of K value from 0, 0.25, 0.5, 0.75, the failure mode of rock mass is approximate, and finally two main cracks in vertical direction consistent with the direction of maximum compressive stress are formed. However, the final crack length decreases gradually, which indicates that the larger the stress ratio is, the less likely the rock mass will be destroyed. (2) the peak value of explosion stress wave has an important influence on crack propagation, and the larger the peak value is, the stronger the crack propagation ability is. (3) when the stress ratio is K 鈮，

本文編號：2483298