第十章I節(jié)理和斷層的力學(xué)基礎(chǔ)：巖石的脆性破裂和摩擦滑動

1、第十章節(jié)理和斷裂的力學(xué)基礎(chǔ):巖石的脆性破裂和摩擦滑動參考書目：Fossen, Structural Geology, Chapter 7巖石的脆性破裂（fracture）破裂（fracture）破裂構(gòu)造的兩方面特征：1）斷裂存在裂隙，地質(zhì)體不再連續(xù)；2）位移（沿破裂面）a）沒有位移節(jié)理節(jié)理b）有位移斷層斷層如果裂隙被礦物充填脈體脈體節(jié)理（joint）斷層（fault）脈體（vein）斷層斷層節(jié)理節(jié)理周口店龍門口周口店龍門口破裂的方式A. 拉張破裂（模式I）：相對運動方向垂直于破裂面B. 剪切破裂（模式II）：相對運動方向平行于破裂面，但垂直于破裂邊緣C. 剪切破裂（模式III）：相對運動方向平

2、行于破裂面和破裂邊緣破裂的方式巖石的破裂方式破裂的力學(xué)分析3 31 12 2物體中與3垂直的平面內(nèi)任意截面的應(yīng)力狀態(tài)都可以用左側(cè)應(yīng)力莫爾圓上的一點來表示。12破裂的力學(xué)分析45 vs. 30 巖石斷裂準(zhǔn)則斷裂是指由于外力作用在物體中產(chǎn)生的介質(zhì)不連是指由于外力作用在物體中產(chǎn)生的介質(zhì)不連續(xù)面。續(xù)面。v斷裂準(zhǔn)則：在極限應(yīng)力狀態(tài)下各點極限應(yīng)力分量所應(yīng)滿足的條件，稱為斷裂條件或者準(zhǔn)則。v莫爾包絡(luò)線：就是材料破壞時的各種極限應(yīng)力狀態(tài)應(yīng)力圓的公切線。判別條件：當(dāng)一點的應(yīng)力狀態(tài)的應(yīng)力圓與莫爾包絡(luò)線相切，這點就開始破裂。張裂的破裂準(zhǔn)則庫侖準(zhǔn)則庫侖準(zhǔn)則，又稱最大剪應(yīng)力準(zhǔn)則，其表達式其表達式為為 max=(1-3)

3、/2=0。022庫侖納維葉(Coulomb-Navier)破裂準(zhǔn)則格里菲斯破裂準(zhǔn)則 該準(zhǔn)則認(rèn)為該準(zhǔn)則認(rèn)為, 任何脆性材料任何脆性材料, 都存在大都存在大量的微小裂縫量的微小裂縫, 脆性材料的斷裂就是由脆性材料的斷裂就是由這些微小的、無定向裂縫擴展的結(jié)果。這些微小的、無定向裂縫擴展的結(jié)果。當(dāng)材料受力時當(dāng)材料受力時, 在微裂縫周圍在微裂縫周圍, 特別是特別是在裂縫尖端發(fā)生應(yīng)力集中在裂縫尖端發(fā)生應(yīng)力集中, 使裂縫擴展使裂縫擴展, 最后導(dǎo)致材料完全破壞。為此最后導(dǎo)致材料完全破壞。為此, 格里菲格里菲斯提出了雙軸應(yīng)力狀態(tài)下裂縫開始擴斯提出了雙軸應(yīng)力狀態(tài)下裂縫開始擴展的判別式展的判別式: 2=4t (t

4、-) 式中式中為斷裂面上的剪應(yīng)力為斷裂面上的剪應(yīng)力, 為斷裂面為斷裂面上的正應(yīng)力上的正應(yīng)力, t為巖石的抗張強度。該為巖石的抗張強度。該式表明式表明, 斷裂的所有極限應(yīng)力圓的包絡(luò)斷裂的所有極限應(yīng)力圓的包絡(luò)線是一條拋物線。線是一條拋物線。格里菲斯破裂準(zhǔn)則vs.庫倫納維葉破裂準(zhǔn)則格里菲斯庫倫破裂準(zhǔn)則斷裂（fault）的微觀機制Lockner, 1991Scholz, 1968脆性破裂的聲發(fā)射脆性破裂的聲發(fā)射斷裂的微觀機制：張裂隙的增生和自組織斷裂的微觀機制：張裂隙的增生和自組織脆性破裂的微觀機制：微破裂？脆性破裂的微觀機制：微破裂？缺陷導(dǎo)致的應(yīng)力集中缺陷導(dǎo)致的應(yīng)力集中張裂張裂(mode I)(mo

5、de I)的產(chǎn)生和傳播的產(chǎn)生和傳播張裂張裂Scholz, 1990剪裂（剪裂（mode IImode II）的產(chǎn)生和傳播的產(chǎn)生和傳播巖石的摩擦滑動（friction sliding）脆性破裂脆性破裂 vsvs摩擦滑動摩擦滑動摩擦（Friction） Once a fault has been formed its further motion is controlled by friction, which is a contact property rather than a bulk property. Friction is the resistance to motion that o

6、ccurs when a body is slid tangentially to a surface on which it contacts another body. Friction is not a fundamental force, as it is derived from electromagnetic force between charged particles, including electrons, protons, atoms, and molecules, and so cannot be calculated from first principles, bu

7、t instead must be found empirically. When contacting surfaces move relative to each other, the friction between the two surfaces converts kinetic energy into thermal energy, or heat. Contrary to earlier explanations, kinetic friction is now understood not to be caused by surface roughness but by che

8、mical bonding between the surfaces. Surface roughness and contact area, however, do affect kinetic friction for micro- and nano-scale objects where surface area forces dominate inertial forces.突起（asperities) & 接觸面（contact area）摩擦的本質(zhì)：突起相互作用庫倫（Coulomb）摩擦 Coulomb friction, named after Charles-Augus

9、tin de Coulomb, is a model used to calculate the force of dry friction. It is governed by the equation: = n is either the force exerted by friction or in the case of equality, the maximum possible magnitude of this force; is the coefficient of friction, which is an empirical property of the contacti

10、ng materials;n is the normal force exerted between the surfaces.There are two different types of Coulomb frictions: static friction and kinetic friction.Byerlees lawByerlees law粘滑（粘滑（Stick slipStick slip）和穩(wěn)滑（）和穩(wěn)滑（stable slidingstable sliding）粘滑粘滑穩(wěn)滑穩(wěn)滑彈簧滑塊模型彈簧滑塊模型摩擦滑動實驗粘滑和穩(wěn)滑的觀測粘滑和穩(wěn)滑與溫度和空隙水壓力關(guān)系Rate and

11、 state (dependent friction) law- Dieterich-Ruina lawRate and state (dependent friction) law- Dieterich-Ruina lawDieterich, J. 1994. A constitutive law for rate of earthquake production and its application to earthquake clustering. JGR, vol. 99, 2601-2618.實習(xí)作業(yè)實習(xí)作業(yè)基本格式基本格式圖名比例尺比例尺方位圖例02004006002004006000（m）AB125452.5cm地層分界線長1.5cm一般巖性符號長注意：方位、比例尺、圖名、圖例是圖切剖面及一切野外素描圖件注意：方位、比例尺、圖名、圖例是圖切剖面及一切野外素描圖件中必不可少的基本要素。中必不可少的基本要素。通知通知期末考試時間：期末