發(fā)布時(shí)間：2018-07-01 12:01

  本文選題：莫高窟 + 落石�。� 參考：《蘭州大學(xué)》2017年碩士論文

【摘要】：莫高窟位于西北內(nèi)陸腹地,自然條件惡劣,風(fēng)化營(yíng)力強(qiáng)烈。在各種自然因素和人為因素下,莫高窟崖體那些裸露的崖面和崖頂緩坡部位遭受了嚴(yán)重的風(fēng)化侵蝕,出現(xiàn)了落石問題,這不僅影響了洞窟的穩(wěn)定和洞窟內(nèi)文物的安全,也對(duì)崖底游客的安全帶來了隱患。國(guó)內(nèi)外關(guān)于邊坡落石方面的研究主要集中于鐵路、公路等線路工程邊坡落石問題,研究的重點(diǎn)都是由崩塌導(dǎo)致的大型崩塌型落石,針對(duì)大型遺址區(qū)的小型落石研究尚不深入,因此,有必要對(duì)大型遺址區(qū)內(nèi)的落石問題進(jìn)行專門研究。本文在前人的研究基礎(chǔ)上,通過落石現(xiàn)場(chǎng)試驗(yàn)、恢復(fù)系數(shù)現(xiàn)場(chǎng)試驗(yàn)、落石運(yùn)動(dòng)軌跡模擬等手段,對(duì)莫高窟落石的成因、主要來源區(qū)、運(yùn)動(dòng)規(guī)律、風(fēng)險(xiǎn)監(jiān)測(cè)等進(jìn)行了一系列研究。得到以下主要結(jié)論:(1)莫高窟落石源區(qū)主要有兩個(gè):崖體上部斜坡和中部侵蝕臺(tái)階。崖體上部斜坡上主要發(fā)育轉(zhuǎn)石型落石,現(xiàn)在是莫高窟景區(qū)落石災(zāi)害的主要來源;中部侵蝕臺(tái)階發(fā)育的剝離型落石主要是由于不同巖組之間、相同巖組內(nèi)部互層間的差異性風(fēng)化引起的,一旦發(fā)生,后果嚴(yán)重,但現(xiàn)在不是景區(qū)內(nèi)落石的主要來源。(2)現(xiàn)場(chǎng)試驗(yàn)中將莫高窟緩坡上的落石按照形狀劃分為四類:近球體、扁平體、長(zhǎng)柱體和長(zhǎng)棱體。四種形狀的落石在運(yùn)動(dòng)過程中具有共性,均以滾動(dòng)和彈跳這兩種形態(tài)為主。所有形狀的落石大部分仍然停留在崖頂緩坡上,只有大約20%的落石會(huì)一次性運(yùn)動(dòng)到崖底的景區(qū)。落石受坡面微地貌影響,落石在下落過程中逐漸向坡面上的沖溝、凹槽內(nèi)匯集。(3)不同質(zhì)量的落石對(duì)地形的抗干擾能力不同。大質(zhì)量落石在運(yùn)動(dòng)過程中受植被、坡面起伏阻尼的影響相對(duì)較小,表現(xiàn)出更大的“抗地形干擾”能力,從而擁有較大的動(dòng)能和運(yùn)動(dòng)距離。小質(zhì)量落石受植被、坡面地貌起伏阻尼的影響更大,運(yùn)動(dòng)過程表現(xiàn)出更明顯的隨機(jī)性特點(diǎn)。近球體落石在運(yùn)動(dòng)過程中水平偏移的距離比扁平體落石的偏移比大;長(zhǎng)棱體、長(zhǎng)柱體落石的偏移比會(huì)隨著其長(zhǎng)細(xì)比的增加而增加。(4)通過比較最終停止運(yùn)動(dòng)點(diǎn)與水平距離的關(guān)系,RocFall的模擬結(jié)果與現(xiàn)場(chǎng)試驗(yàn)的結(jié)果比較吻合。模擬結(jié)果顯示,落石20%一次性滾落崖底,變成了景區(qū)的落石災(zāi)害;80%的落石停留在了崖頂緩坡上,其中多半停留在了5m的范圍之內(nèi)。落石在莫高窟崖頂緩坡上運(yùn)動(dòng)時(shí),落石的主要運(yùn)動(dòng)形態(tài)以滾動(dòng)和滑動(dòng)為主,間有少許的彈跳,落石的彈跳高度很小,在0.1-0.2m的范圍之內(nèi)。落石的總靜能和平移速度亦沒有很大的變化。在落石沖出崖眉并碰撞到擋土墻頂端的這段過程中,主要的運(yùn)動(dòng)形態(tài)是墜落,落石的總靜能和速度均急劇增加。
[Abstract]:Mogao Grottoes located in the hinterland of the northwest, natural conditions are harsh, weathering force is strong. Under various natural and human factors, the exposed cliff surface and the gentle slope of the cliff top of the Mogao Grottoes have suffered serious weathering and erosion, resulting in the problem of falling stones, which not only affects the stability of the grottoes and the safety of the cultural relics in the caves. It also brings hidden danger to the security of tourists at the bottom of the cliff. At home and abroad, the research on slope rock fall is mainly focused on the slope falling problem of railway, highway and other railway projects. The focus of the research is the large-scale collapse type rock falling caused by the collapse, but the research on the small rock fall in the large site area is not deep. Therefore, it is necessary to study the problem of falling stone in large site area. On the basis of previous studies, this paper has carried out a series of studies on the origin, main source area, movement law and risk monitoring of the falling stone in Mogao Grottoes by means of the field test of falling stone, the field test of recovery coefficient and the simulation of the movement track of falling stone in Mogao Grottoes. The main conclusions are as follows: (1) there are two main sources of rock fall in Mogao Grottoes: the upper slope of the cliff body and the erosion steps in the middle part. On the slope of the upper slope of the cliff, the rock falling type is mainly developed, which is now the main source of the rock falling disaster in the Mogao Grottoes, and the peeling type of stone falling in the middle erosion steps is mainly due to the different rock formations. The difference of weathering between interlayers in the same rock formation, once it occurs, has serious consequences, but now it is not the main source of falling stones in scenic spots. (2) in the field tests, the falling stones on the gentle slopes of the Mogao grottoes are divided into four categories according to their shape: near spheres, Flat bodies, long columns and long prisms. The four kinds of falling stones have the common character in the course of movement, and they are mainly rolling and bouncing. Most of the falling stones of all shapes remain on the gentle slope of the cliffs, and only about 20% of them will move to the scenic spots at the bottom of the cliffs at one time. The falling stone is influenced by the microgeomorphology of the slope, and the falling stone gradually converges into the gully and the groove in the falling process. (3) the anti-interference ability of the different quality of the falling stone to the topography is different. Large mass rock fall is affected by vegetation and slope undulating damping in the process of movement, which shows greater ability to resist terrain interference and thus has larger kinetic energy and moving distance. The small mass rock fall is affected by vegetation, the slope landform undulation damping is more influence, and the movement process shows more obvious randomness characteristic. The distance of horizontal deviation in the course of movement is larger than that of flat body. The deviation ratio of long column falling stone will increase with the increase of slenderness ratio. (4) by comparing the relationship between the final stop point and horizontal distance, the simulation results of RocFall are in good agreement with the field test results. The simulation results show that 20% of the falling rocks fall on the bottom of the cliffs at one time, and 80% of the falling rocks stay on the gentle slope of the cliffs, and most of them stay within the range of 5m. When the falling stone moves on the gentle slope of the top of the Mogao Grottoes, the main motion forms of the falling stone are mainly rolling and sliding, and there is a little bouncing between them, and the height of the falling stone is very small, within the range of 0.1-0.2 m. The total static energy and the translation velocity of the falling stone have no great change. In the process of falling stone rushing out of the brow of the cliff and colliding to the top of the retaining wall, the main motion form is falling, and the total static energy and velocity of falling stone increase sharply.
【學(xué)位授予單位】：蘭州大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：P642.2

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