本文選題：巖溶　切入點(diǎn)：巖溶地基　出處：《廣西科技大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：論文以廣西柳州白云巖強(qiáng)巖溶發(fā)育區(qū)天然地基為研究基礎(chǔ),以柳州白云巖強(qiáng)巖溶發(fā)育區(qū)的巖溶塌陷地質(zhì)災(zāi)害為分析對(duì)象,分析總結(jié)了柳州白云巖強(qiáng)巖溶發(fā)育區(qū)巖溶塌陷的主要影響因素,通過(guò)引入層次分析法對(duì)主要影響因素進(jìn)行分類,在此基礎(chǔ)上結(jié)合工程實(shí)例,運(yùn)用層次分析法對(duì)柳州白云巖強(qiáng)巖溶發(fā)育區(qū)某一場(chǎng)地巖溶塌陷的危險(xiǎn)性進(jìn)行分區(qū)。而后結(jié)合柳州白云巖強(qiáng)巖溶發(fā)育區(qū)巖體力學(xué)性能,運(yùn)用圓板小撓度理論和數(shù)值分析軟件分析研究了溶洞頂板的穩(wěn)定性問(wèn)題;論文考慮人類工程活動(dòng)對(duì)天然地基穩(wěn)定性的影響,研究了地下水位升降過(guò)程中土洞的擴(kuò)展機(jī)理及其周圍的應(yīng)力應(yīng)變分布規(guī)律;在抽水情況下,考慮抽水量對(duì)極限水力坡度的影響分析了抽水量的大小對(duì)場(chǎng)地穩(wěn)定性的影響并探討了場(chǎng)地(土洞)距抽水井的安全距離問(wèn)題;通過(guò)前述研究工作,主要取得了如下認(rèn)識(shí)與成果:(1)柳州白云巖強(qiáng)巖溶發(fā)育區(qū)巖溶塌陷主要受淺層巖溶發(fā)育程度、地形地貌、地層巖性、地下水活動(dòng)及人類工程活動(dòng)的影響。其中巖溶發(fā)育程度、地形地貌、地層巖性、地下水活動(dòng)是產(chǎn)生巖溶塌陷的自然因素,而人類工程活動(dòng)是加快巖溶塌陷的主要誘發(fā)因素。(2)厚跨比的不同對(duì)溶洞頂板最大拉應(yīng)力的影響程度差別較大。厚跨比大于0.5時(shí)對(duì)頂板最大應(yīng)力的影響較小,但厚跨比小于0.5時(shí)對(duì)頂板最大應(yīng)力有顯著的影響,且隨著厚跨比的減小,最大應(yīng)力急劇增大。(3)樁徑小于溶洞頂板跨度時(shí),除考慮厚跨比對(duì)溶洞頂板穩(wěn)定性的影響外還應(yīng)考慮跨徑比的影響。對(duì)于邊界固定的溶洞頂板,跨徑比對(duì)其彎矩和拉應(yīng)力的分布影響較顯著,當(dāng)跨徑比小于2.2時(shí),頂板彎矩及拉應(yīng)力的最大值均在邊界處取得。當(dāng)跨徑比大于2.2時(shí),彎矩及拉應(yīng)力最大值則于頂板中心取得;邊界簡(jiǎn)支時(shí)彎矩及拉應(yīng)力均在其中心有最大值。但最大剪應(yīng)力則與跨徑比無(wú)關(guān),都于頂板外邊緣處取得最大值。(4)地下水活動(dòng)對(duì)土洞的擴(kuò)展表現(xiàn)出一系列影響,地下水位的升降直接導(dǎo)致土洞周圍土體塑性區(qū)與彈性區(qū)范圍發(fā)生改變,并導(dǎo)致土體應(yīng)力應(yīng)變及變形不斷變化,于彈塑性交界面附近形成松動(dòng)圈促進(jìn)土洞的擴(kuò)大。(5)當(dāng)樁徑大于或等于溶洞頂板跨度且溶洞頂板巖體基本質(zhì)量級(jí)別為Ⅱ、Ⅲ級(jí)時(shí),把厚跨比大于1.0的溶洞頂板判定為穩(wěn)定,其安全系數(shù)大于1.4,此時(shí)溶洞頂板有足夠的安全儲(chǔ)備。
[Abstract]:This paper takes the natural foundation of the strong karst development area of Liuzhou dolomite in Guangxi as the research foundation, and takes the karst collapse geological hazard in the strong karst area of Liuzhou dolomite as the analysis object. This paper analyzes and summarizes the main influencing factors of karst collapse in the strong karst area of Liuzhou dolomite, classifies the main influencing factors by introducing the analytic hierarchy process (AHP), and on this basis combines with an engineering example. The risk of karst collapse in a site in a strong karst area of Liuzhou dolomite is divided by analytic hierarchy process (AHP), and then combined with the mechanical properties of rock mass in the strong karst area of Liuzhou dolomite. The stability of cavern roof is studied by using circular plate small deflection theory and numerical analysis software, and the influence of human engineering activities on the stability of natural foundation is considered in this paper. In this paper, the spreading mechanism of soil tunnel and its stress and strain distribution in the process of groundwater level rise and fall are studied, and in the case of pumping water, Considering the influence of pumping capacity on the limit hydraulic gradient, this paper analyzes the influence of pumping quantity on site stability and discusses the safe distance between site (earth hole) and pumping well. The main achievements are as follows: (1) Karst collapse in the strong karst area of Liuzhou dolomite is mainly affected by the degree of shallow karst development, topography, stratigraphic lithology, groundwater activity and human engineering activity. Topography and landform, stratigraphic lithology and groundwater activity are the natural factors that cause karst collapse. However, human engineering activity is the main inducing factor of accelerating karst collapse. The difference of thickness span ratio on the maximum tensile stress of karst cavern roof is great. When the thickness span ratio is greater than 0.5, the influence of thickness span ratio on the maximum roof stress is relatively small. However, when the ratio of thickness to span is less than 0.5, it has a significant effect on the maximum stress of the roof, and with the decrease of the ratio of thickness to span, the maximum stress increases sharply when the diameter of the pile is smaller than the span of the roof of the cavern. In addition to considering the influence of thickness to span ratio on the stability of the roof of a karst cave, the influence of span ratio on the distribution of bending moment and tensile stress is significant for the roof of a karst cave with fixed boundary, when the span ratio is less than 2.2, The maximum values of bending moment and tensile stress are obtained at the boundary. When the span ratio is greater than 2.2, the maximum value of bending moment and tensile stress is obtained at the center of the roof. When the boundary is simply supported, the bending moment and tensile stress have the maximum value in the center of the boundary, but the maximum shear stress is independent of the span ratio and reaches the maximum value at the outer edge of the roof. 4) the groundwater activity shows a series of effects on the expansion of the soil tunnel. The rise and fall of groundwater level directly change the plastic zone and elastic zone of soil around the soil tunnel, and cause the continuous change of stress, strain and deformation of soil. When the diameter of pile is greater than or equal to the roof span of the karst cave and the basic quality grade of the rock mass of the karst cave is grade 鈪，

本文編號(hào)：1587693