本文選題：砂巖表層 + 溫度效應(yīng)��； 參考：《中國(guó)地質(zhì)大學(xué)》2012年碩士論文

【摘要】：云岡石窟是依據(jù)自然崖壁山體開(kāi)鑿營(yíng)建而成,既是建筑體(或構(gòu)筑物),又是地質(zhì)體。石窟賦存于地質(zhì)環(huán)境之中,在漫長(zhǎng)的歷史時(shí)期受地質(zhì)構(gòu)造和各種地質(zhì)營(yíng)力的影響,產(chǎn)生了各種環(huán)境地質(zhì)病害,導(dǎo)致石窟巖體發(fā)生破壞,嚴(yán)重威脅了石窟的保存�，F(xiàn)場(chǎng)調(diào)查發(fā)現(xiàn),石窟立壁巖體表層片狀開(kāi)裂是云岡石窟的主要病害之一。石窟巖體表層是雕刻藝術(shù)品的載體,表層的開(kāi)裂剝落既破壞了石窟的雕刻藝術(shù),同時(shí)又會(huì)弱化巖體的物理力學(xué)性質(zhì),導(dǎo)致洞窟失穩(wěn),如窟前立柱表層的不斷剝落最終會(huì)導(dǎo)致洞窟失穩(wěn)破壞。 云岡石窟砂巖表層溫度效應(yīng)劣化研究,是國(guó)家科技支撐計(jì)劃項(xiàng)目“石質(zhì)文物保護(hù)關(guān)鍵技術(shù)”之“石窟巖體穩(wěn)定性分析研究”課題(編號(hào)：2009BAK53B03)的重要內(nèi)容。本文的主要研究成果如下： (1)溫差變化在云岡石窟巖體風(fēng)化中的物理作用機(jī)制,分為巖體的熱脹冷縮和含水巖體的冰劈作用�，F(xiàn)場(chǎng)調(diào)查發(fā)現(xiàn),在巖體總體穩(wěn)定性完好的石窟區(qū),巖體表層的失穩(wěn)破壞形式主要表現(xiàn)為崖壁巖體表層的片狀開(kāi)裂以及剝落。此類(lèi)開(kāi)裂體通常是溫差應(yīng)力下巖體表層沿原生微結(jié)構(gòu)面拉裂擴(kuò)展而成。因此,有必要研究環(huán)境氣溫變化對(duì)云岡石窟巖體的影響深度及巖體表層溫度場(chǎng)隨季節(jié)的變化規(guī)律。由巖體熱物理參數(shù)測(cè)試可知,云岡砂巖的主要熱物理參數(shù)：λ=3.516[W/(m·k)],0℃-35℃內(nèi),云岡石窟砂巖比熱為0.63[J/(m3·℃],35℃-60℃內(nèi),比熱為0.85[J/(m3.℃]；線膨脹系數(shù)α為11.7×10-6(1/K)。由溫度的現(xiàn)場(chǎng)監(jiān)測(cè)結(jié)果可知,云岡石窟砂巖表面溫度與環(huán)境溫度成正相關(guān),呈現(xiàn)周期性變化。巖體內(nèi)部各處溫度隨深度的變化也具有一定的周期性,同時(shí)反映了巖體在日夜交替環(huán)境下存在一定深度的熱量交換,得出云岡砂巖日變溫帶范圍為0-50cm。監(jiān)測(cè)表明在0-5cm范圍內(nèi)溫度梯度最大,是溫度應(yīng)力較明顯部位。采用熱傳導(dǎo)微分方程解算溫度場(chǎng)時(shí)需要進(jìn)行適當(dāng)假定。采用Maple軟件能解決偏微分方程計(jì)算工作量大的問(wèn)題。 (2)云岡石窟地區(qū)屬于寒區(qū),由現(xiàn)場(chǎng)溫度監(jiān)測(cè)結(jié)果可知,冬季石窟巖體溫度長(zhǎng)期低于0℃。巖體裂隙中水分在低溫下發(fā)生相變,水結(jié)冰的過(guò)程中對(duì)巖體形成凍脹力。試驗(yàn)凍融前后在形態(tài)上出現(xiàn)顆粒脫落甚至斷裂破壞,體積普遍膨脹,質(zhì)量下降,縱波波速下降。且隨著凍融循環(huán)次數(shù)的增加,上述物理指標(biāo)也隨之降低。試驗(yàn)凍融巖樣的單軸抗壓強(qiáng)度降低,隨著凍融循環(huán)次數(shù)增加,強(qiáng)度衰減加劇。依據(jù)巖樣的波速與單軸抗壓強(qiáng)度建立了二者關(guān)系曲線。試驗(yàn)中對(duì)巖樣S-6-1/S-6-2/S-2-3分別進(jìn)行實(shí)時(shí)變形監(jiān)測(cè)。通過(guò)監(jiān)測(cè)結(jié)果發(fā)現(xiàn)原生缺陷(縱向裂隙或水平裂隙)對(duì)巖樣的軸向應(yīng)變和徑向應(yīng)變影響較大。試驗(yàn)凍融前后巖樣的微觀結(jié)構(gòu)發(fā)生明顯變化。隨著凍融循次數(shù)的增加,巖樣內(nèi)部結(jié)構(gòu)愈疏松,微裂紋不斷擴(kuò)展。通過(guò)對(duì)試驗(yàn)結(jié)果的分析,得出云岡石窟砂巖的凍融循環(huán)破壞機(jī)理。砂巖的凍融破壞主要是由巖體所含水分的相變引起。根據(jù)現(xiàn)場(chǎng)破壞情況及室內(nèi)試驗(yàn)損傷情況總結(jié)出云岡石窟砂巖凍融循環(huán)破壞呈現(xiàn)片狀剝落和裂紋擴(kuò)展兩種劣化模式。 (3)對(duì)于溫度場(chǎng)對(duì)巖體的影響要分為低溫和高溫進(jìn)行處理分析。高溫時(shí)主要考慮巖體自身的熱應(yīng)力,低溫時(shí)要同時(shí)考慮巖體中水分相變產(chǎn)生的凍脹力。邊界條件的設(shè)置與荷載的施加準(zhǔn)確的前提下,采用ANSYS進(jìn)行溫度場(chǎng)分布的數(shù)值模擬是較切合現(xiàn)場(chǎng)監(jiān)測(cè)試驗(yàn)結(jié)果的。在高溫條件下,進(jìn)行巖體的熱力耦合時(shí),巖體的應(yīng)力、應(yīng)變均出現(xiàn)增大趨勢(shì)。在升溫和降溫循環(huán)反復(fù)作用下,巖體出現(xiàn)應(yīng)力反復(fù)變化,導(dǎo)致巖體出現(xiàn)一定的損傷。在云岡石窟地區(qū)的窟檐立柱長(zhǎng)期處于應(yīng)力調(diào)整中,不僅對(duì)立柱本身產(chǎn)生損傷,對(duì)其上的砂巖窟檐也會(huì)出現(xiàn)拉壓破壞。在低溫條件下,進(jìn)行巖體的熱力耦合時(shí),巖體的應(yīng)力、應(yīng)變均出現(xiàn)增大趨勢(shì)。尤其在低溫下含水裂隙處出現(xiàn)相變,導(dǎo)致該部位出現(xiàn)相對(duì)的應(yīng)力集中、應(yīng)變?cè)龃蟆?本文的創(chuàng)新點(diǎn)主要表現(xiàn)在： (1)采用自主研制的溫度現(xiàn)場(chǎng)監(jiān)測(cè)設(shè)備,獲取了云岡石窟砂巖淺層溫度一個(gè)氣象年的完整數(shù)據(jù),為今后該地區(qū)巖體淺層溫度場(chǎng)的研究工作奠定了數(shù)據(jù)基礎(chǔ)。首次對(duì)云岡石窟大氣及淺層巖體的溫度變化規(guī)律進(jìn)行分析。結(jié)合云岡砂巖熱物理參數(shù),建立了該地區(qū)淺層巖體的溫度分布統(tǒng)計(jì)學(xué)公式。 (2)課題組自主研制變形監(jiān)測(cè)設(shè)備,在常規(guī)凍融試驗(yàn)的基礎(chǔ)上增加凍結(jié)過(guò)程的徑向、軸向的位移監(jiān)測(cè),揭示云岡砂巖的凍結(jié)劣化過(guò)程。 (3)采用ANSYS軟件對(duì)高溫下石窟立柱進(jìn)行熱力耦合分析,揭示該立柱風(fēng)化的熱力學(xué)本質(zhì)。在巖體裂隙水低溫相變的條件下,對(duì)石窟區(qū)某邊坡進(jìn)行熱力耦合分析,得出凍結(jié)條件下巖體局部穩(wěn)定性降低的結(jié)論。
[Abstract]:Yungang Grottoes is built on the basis of the excavation of the natural cliff mountain, which is both the building body (or structure) and the geological body. The grottoes are located in the geological environment. In the long historical period, the geological structures and various geological camping forces have caused various environmental geological diseases, resulting in the destruction of the grotto rock mass and the serious threat to the grottoes. It is found that the crack in the surface layer of the Grottoes is one of the main diseases of the Yungang Grottoes. The surface of the grotto rock mass is the carrier of the sculptured art. The cracking and peeling of the surface not only destroys the carving art of the grottoes, but also weakens the physical and mechanical properties of the rock mass, which leads to the instability of the grottoes, such as the continuous stripping of the surface of the front column of the grottoes. The collapse of the cave eventually leads to the failure of the caves.
The study on the surface temperature effect deterioration of the Yungang Grottoes sandstone is the important content of the "rock mass stability analysis study" (number: 2009BAK53B03) of the national science and technology support project "key technology of stone cultural relic protection" (number: 2009BAK53B03). The main achievements of this paper are as follows:
(1) the physical mechanism of the variation of the temperature difference in the weathering of the rock mass of the Yungang Grottoes is divided into the thermal expansion and contraction of the rock mass and the ice splitting of the hydrous rock mass. So it is necessary to study the influence depth of the environmental temperature change on the rock mass of the Yungang Grottoes and the change law of the surface temperature field of the rock mass with the season. It is known that the main thermal physical parameters of Yungang sandstone are lambda =3.516[W/ (M. K)], 0 C -3. Within 5 C, the specific heat of the Yungang Grottoes sandstone is 0.63[J/ (M3. C), the specific heat is 0.85[J/ (m3. C) and the coefficient of linear expansion is 11.7 * 10-6 (1/K) within 35 C -60 C. It is known that the temperature of the sandstone surface has a positive correlation with the environmental temperature, and shows a periodic change. At the same time, it reflects a certain depth of heat exchange in the rock mass in the environment of day and night. It is concluded that the range of 0-50cm. monitoring shows that the temperature gradient of the diurnal temperature zone of Yungang sandstone is the largest in the range of 0-5cm, and the temperature stress is more obvious. Maple software can solve the problem of heavy computation of PDE.
(2) the Yungang Grottoes area belongs to the cold region. It is known from the field temperature monitoring results that the temperature of rock mass in the winter Grottoes is lower than 0 C. the moisture of the rock mass in the rock fracture occurs at low temperature, and the frost heave force is formed in the process of water freezing. With the increase of the freezing thawing cycle times, the above physical indexes also decrease. The uniaxial compression strength of the test freeze-thaw rock decreases. With the increase of the freezing thawing cycle times, the intensity attenuation increases. According to the wave velocity and the uniaxial compressive strength of the rock samples, the two relation curves are set up. In the test, the rock sample S-6-1/S-6-2/S-2-3 is respectively in the test. Real time deformation monitoring is carried out. Through monitoring results, it is found that primary defects (longitudinal fissures or horizontal fractures) have great influence on the axial and radial strain of rock samples. The microstructure of rock samples changes obviously before and after freezing and thawing. With the increase of freezing thawing times, the internal structure of rock samples is looser and the micro cracks continue to expand. The failure mechanism of the freeze-thaw cycle of the Yungang Grottoes sandstone is analyzed. The frost thawing failure of the sandstone is mainly caused by the phase change of the water content in the rock mass. According to the damage of the site and the damage of the indoor test, it is concluded that the damage of the freeze-thaw cycle of the Yungang Grottoes is two deterioration patterns of flake flake and crack growth.
(3) the influence of temperature field on rock mass should be divided into low temperature and high temperature. The thermal stress of rock mass is mainly considered at high temperature. At low temperature, the frost heaving force produced by water phase change in rock mass should be considered at the same time. Under the premise of setting the boundary condition and applying the load accurately, the numerical simulation of the distribution of temperature field is carried out by ANSYS. Under the thermal coupling of rock mass, the stress and strain of rock mass appear to be increased under the thermal coupling of rock mass under the condition of high temperature. Under the repeated action of heating and cooling cycle, the rock mass appears repeated changes, which leads to a certain damage in the rock mass. The grotto column in the Yungang Grottoes area is in the stress adjustment for a long time. At low temperature, the stress and strain of rock mass appear to increase, especially in the water cut cracks at low temperature, which leads to the relative stress concentration and strain increase.
The main innovation points of this paper are as follows:
(1) to obtain the complete data of a meteorological year of the shallow temperature of the sandstone in the Yungang Grottoes by using the self developed temperature field monitoring equipment, which has laid the data foundation for the study of the shallow temperature field of the rock mass in the area in the future. The temperature change law of the atmosphere and shallow rock in the Yungang Grottoes is analyzed for the first time. The statistical formula for the temperature distribution of shallow rock mass in this area is established.
(2) the project group independently developed the deformation monitoring equipment. On the basis of the conventional freezing and thawing test, the radial and axial displacement monitoring of the freezing process was added to reveal the freezing and deterioration process of the Yungang sandstone.
(3) ANSYS software is used to analyze the thermomechanical coupling of the grottoes at high temperature to reveal the thermodynamic essence of the column weathering. Under the condition of the low temperature phase change of the fractured water in the rock mass, the thermodynamic coupling analysis of a slope in the Grottoes is carried out, and the conclusion that the local stability of the rock mass is reduced under the freezing condition is obtained.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2012
【分類(lèi)號(hào)】：K879.22;P642

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