本文選題：高山 + 河谷　； 參考：《山東大學》2015年碩士論文

【摘要】：高山河谷地區(qū)具有特殊的地質地貌特征。復雜的地質構造作用和河谷表面長期受到的風化作用,使高山河谷地區(qū)原有的應力場重新分布和調整,形成了該地區(qū)現(xiàn)今特殊的地應力場分布。另外,由于河谷地區(qū)地質構造復雜,現(xiàn)代構造活動強烈,邊坡巖體內節(jié)理裂隙發(fā)育。節(jié)理裂隙的存在,使巖體表現(xiàn)出很強的非均質性、不連續(xù)性和各向異性,影響巖體的強度和變形特性。在高山河谷地區(qū)進行地下工程,必然引起影響范圍內巖體的變形,隨之發(fā)生地應力的釋放和調整,對節(jié)理圍巖的穩(wěn)定性產生影響。因而,針對修建于高山河谷地區(qū)的地下工程,需要結合地應力場的分布規(guī)律和節(jié)理巖體的力學特性來分析工程的穩(wěn)定性。本文首先利用有限差分軟件FLAC-3D對高山河谷地區(qū)地應力場的分布特征進行了研究。分別考慮了地形地貌、自重作用、構造應力、風化等因素對高山河谷地區(qū)地應力場的影響：(1)不同的山體坡度會對初始地應力的分布產生十分重要的影響。通過數(shù)值分析研究了當山體坡度不同時,在重力場條件下以及不同地應力側壓力系數(shù)時山體中水平向典型剖面中初始地應力的大小與分布的特點。得到了在水平方向上距坡體表面一定范圍內存在坡面效應的結論,且此效應隨山體坡地的增大以及水平向構造應力的增大而越發(fā)明顯。并指出在此區(qū)域內修建地下工程時,不能簡單的取其直接埋深算出的垂直向地應力作為該處的地應力值。(2)在第一步的基礎上,考慮河流下切作用,建立呈“V”字型對稱分布形式的不同坡度河谷模型,同時在河谷表面設置四層不同風化程度的分化帶來模擬風化作用產生的卸荷作用,得到了在考慮風化作用下的河谷地區(qū)地應力分布的特征。將得到的結果與前人通過現(xiàn)場實測得到的地應力場的規(guī)律進行了對比,驗證了河谷地區(qū)地應力場的“駝峰型”分布特征。同時將通過數(shù)值模擬得到的45°河谷在2.25倍水平向地應力作用下的地應力場與二灘水電站現(xiàn)場實測的地應力場相對比,結果十分吻合,驗證了數(shù)值計算結果的正確性。其次,詳細介紹了如何利用模型試驗和數(shù)值方法研究節(jié)理巖體的強度和變形特性。通過對包含有30°、45°、60°三種裂隙傾角的節(jié)理試件和完整試件進行單軸壓縮室內試驗,研究了節(jié)理的存在對巖體的強度及變形特性的影響；結合現(xiàn)場調查的巖體節(jié)理裂隙分布規(guī)律,利用蒙特卡洛方法,生成了隨機節(jié)理數(shù)值試件,并利用數(shù)值加載試驗研究了裂隙隨機分布對節(jié)理巖體強度的影響,研究了巖體特征單元體的REV尺寸和等效力學參數(shù)。第三,提出了一種基于二次型包絡線的巖體強度準則。對滿足REV尺寸的數(shù)值試件模擬不同圍壓下的加載試驗,利用試驗得到的應力應變曲線求解試件的二次包絡線,并以此作為節(jié)理巖體的強度準則,為工程算例的計算奠定了基礎。最后,將通過模型試驗和巖體特征單元體得到的節(jié)理巖體力學參數(shù)與高山河谷地區(qū)地應力場的分布特征將結合,研究了高山河谷地區(qū)地應力場的分布特征對節(jié)理圍巖工程穩(wěn)定性的影響。在V字型河谷地區(qū)和高山地區(qū)山體中不同高程距坡腳3個不同距離分別開挖1個洞室,采用了節(jié)理巖體的等效力學參數(shù)以及室內試驗得到的巖體力學參數(shù)做數(shù)值分析,比較各方案洞室的圍巖穩(wěn)定性狀況,得到以下結論：(1)水平向地應力的作用是影響節(jié)理圍巖穩(wěn)定性的重要因素。一般來說,隨著水平向地應力作用的增大,洞室開挖后,塑性區(qū)體積會增大。不過當洞室處于山體深處時,垂直向成為最大主應力的方向,隨著水平向地應力作用的增大,最大主應力和最小主應力的差值會減小,這對洞室開挖后圍巖的穩(wěn)定性有利,塑性區(qū)會隨著水平向地應力作用的增大而減小。(2)山體的坡面效應是影響節(jié)理圍巖穩(wěn)定性的重要因素。開挖洞室距坡腳越近,塑性區(qū)體積越大,對節(jié)理圍巖穩(wěn)定性越不利。同時也說明了地應力的計算常規(guī)的做法——一律取其上部巖體的直接埋深h作為該點初始垂直向地應力的計算方法——在山體內接近坡面一定距離內是不妥的。(3)在河谷地區(qū),洞室開挖應盡量避開應力峰值區(qū)和應力升高區(qū)。應力升高區(qū)通常為風化區(qū),該區(qū)域內盡管應力水平較低,但由于巖體受到外界的風化作用,巖體力學參數(shù)較低,不利于圍巖穩(wěn)定；而應力峰值區(qū)在同高程應力水平最高,最大主應力與最小主應力的差值也最大,對洞室開挖后圍巖的穩(wěn)定性十分不利；相反,在原巖應力區(qū),最大主應力與最小主應力之間的差值較小,對洞室開挖后圍巖穩(wěn)定性有利。(4)在河谷地區(qū),洞室開挖位置高程越低,對洞室圍巖穩(wěn)定性越不利。產生這一影響的原因在于河谷底部的高應力集中——即“高應力包”的存在。在0m高程,由于距離河谷底部較近,靠近坡腳處本身也可以看做是應力集中區(qū)域,因而應力水平較高,不利于圍巖的穩(wěn)定；隨著高程的增加,受“高應力包”的影響也逐漸減小,應力水平也逐漸降低,因而洞室開挖后塑性區(qū)也逐漸減少。
[Abstract]:The high mountain valley area has special geological and geomorphic features. The complex geological structure and the long-term weathering effect of the valley surface make the original stress field redistributed and adjusted in the alpine valley area, forming a special distribution of the present stress field in this area. In addition, the modern tectonic activity is complicated because of the complex geological structure in the valley area. It is strong that the joints and cracks in the rock slope are developed. The existence of joint cracks causes rock mass to show strong heterogeneity, discontinuity and anisotropy, which affects the strength and deformation characteristics of rock mass. Underground engineering in the alpine valley area is bound to cause the deformation of rock mass within the affected area, and the stress release and adjustment will occur with it. The stability of the surrounding rock is affected. Therefore, for the underground engineering built in the alpine valley area, the stability of the engineering is analyzed in combination with the distribution of the stress field and the mechanical properties of the jointed rock mass. Firstly, the distribution characteristics of the geostress field in the alpine valley area are studied by using the finite difference software FLAC-3D. The influence of topography, gravity, tectonic stress, weathering and other factors on the geostress field in the alpine valley area: (1) the gradient of different mountain slopes will have a very important influence on the distribution of initial geostress. The characteristics of the size and distribution of the initial geostress in a typical profile in a mountain range, the conclusion is drawn that there is a slope effect in a certain range in a horizontal direction to the surface of the slope body, and the effect of this effect is more obvious with the increase of the hill slope and the increase of the horizontal tectonic stress. At the same time, the vertical crustal stress calculated directly by the direct buried depth can not be taken as the geostress value of the site. (2) on the basis of the first step, considering the river cutting action, a different slope Valley model is established in the form of "V" type symmetry distribution. At the same time, the differentiation of different weathering degrees of four layers on the valley surface brings simulated weathering effect. The distribution of ground stress in the valley area under the consideration of weathering is obtained. The results are compared with the law of the ground stress field measured by the predecessors, and the distribution characteristics of the "Hump type" in the ground stress field in the valley area are verified. At the same time, the 45 degree Valley in the river valley is obtained by numerical simulation. The ground stress field under the 2.25 times horizontal stress is compared with the in-situ stress field measured at the two beach hydropower station. The results are in good agreement, and the correctness of the numerical results is verified. Secondly, how to use the model test and numerical method to study the strength and deformation characteristics of jointed rock mass is described in detail. Through the inclusion of 30, 45, 60 degrees, it is described in detail. Three kinds of jointed joints and complete specimens were tested in a single axis compression test, and the influence of the existence of joints on the strength and deformation of rock mass was studied. The influence of the gap random distribution on the strength of jointed rock mass, the REV size and the equivalent mechanical parameters of the rock mass element are studied. Third, a rock mass strength criterion based on the two type envelope is proposed. The loading test under different confining pressure is simulated for the numerical specimen with the size of the REV, and the stress strain curve obtained by the test is used to solve the specimen. The two enveloping line is used as the strength criterion of the jointed rock mass, which lays the foundation for the calculation of the engineering example. Finally, the distribution characteristics of the stress field in the alpine valley area will be combined by the mechanical parameters of the jointed rock mass obtained by the model test and the characteristic element body of the rock mass, and the distribution characteristics of the geostress field in the alpine valley area are studied. The influence on the stability of the Jointed Surrounding Rock Engineering. 1 caverns were excavated at 3 different distances from the foot of different elevation in the V Valley and the mountain areas. The equivalent mechanical parameters of the jointed rock mass and the rock mechanics parameters obtained in the laboratory were numerically analyzed to compare the stability of the surrounding rock. The following conclusions are as follows: (1) the effect of horizontal stress on the ground stress is an important factor affecting the stability of the jointed rock. In general, the volume of the plastic zone will increase with the increase of the horizontal stress on the ground stress, but when the cavern is in the depth of the mountain, the vertical direction becomes the direction of the largest main stress, and the horizontal stress acts along with the horizontal stress. The difference between the maximum principal stress and the minimum principal stress will be reduced, which is beneficial to the stability of the surrounding rock after the excavation of the cavern, and the plastic zone will decrease with the increase of the horizontal stress on the ground. (2) the slope effect of the mountain is an important factor affecting the stability of the jointed rock. The more bad the rock stability is, it also illustrates the conventional method of calculating the stress. It is not appropriate to take the direct buried depth h of the upper rock mass as a calculation method of the initial vertical stress of this point - in a mountain near a certain distance to the slope. (3) in the Valley area, the cave excavation should try to avoid the peak stress zone and stress. The rising area is usually a weathering zone, although the stress level is low in this area, but because of the weathering of the rock mass, the mechanical parameters of rock mass are low and not favorable to the stability of the surrounding rock, and the peak stress zone is the same as the Gao Chengying force, and the difference between the maximum principal stress and the minimum main stress is also the most, and the surrounding rock after the excavation is excavated. On the contrary, the difference between the maximum principal stress and the minimum principal stress is smaller in the original rock stress area, and it is beneficial to the stability of the surrounding rock after the excavation of the cavern. (4) the lower the height of the excavation position in the valley, the more unfavorable to the stability of the surrounding rock. The cause of this effect lies in the high stress concentration at the bottom of the valley. - the existence of "high stress package". In the 0m elevation, as the distance from the bottom of the valley is closer to the bottom of the valley, the stress concentration area can also be seen as a stress concentration area, so the stress level is high and is not conducive to the stability of the surrounding rock. As the elevation increases, the influence of the "high stress package" decreases gradually, and the stress level is gradually reduced, thus caverns open. After digging, the plastic zone is also gradually reduced.

【學位授予單位】：山東大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU452

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本文編號：1850860