【摘要】：在凍結(jié)法施工中,凍結(jié)管的安全穩(wěn)定是影響凍結(jié)施工順利進(jìn)行的關(guān)鍵性因素。近年來,在硬巖地層凍結(jié)法鑿井工程中發(fā)生了多起凍結(jié)管徑向失穩(wěn)擠扁破壞事故,導(dǎo)致凍結(jié)工程失敗,對工程進(jìn)度和效益造成了較大影響。針對這一現(xiàn)象,本文通過解析分析、數(shù)值模擬和物理模擬相結(jié)合的方法對硬巖地層中凍結(jié)管徑向失穩(wěn)的機(jī)理和規(guī)律進(jìn)行全面的研究。首先,建立“凍結(jié)管-已凍泥漿-未凍泥漿-圍巖”多層筒力學(xué)模型,推導(dǎo)未凍泥漿區(qū)凍脹力的解析解,并獲得未凍區(qū)凍脹力與泥漿凍結(jié)壁厚度及各影響因素的變化關(guān)系。其次,基于單管溫度場、單管徑向屈曲和巖石拉裂問題的模擬,對理想情況下受凍脹力作用的凍結(jié)管徑向失穩(wěn)問題進(jìn)行數(shù)值計算。在考慮圍巖水壓致裂的情況下,掌握了凍結(jié)過程中泥漿凍結(jié)壁厚度、凍脹力變化和凍結(jié)管徑向屈曲變形的規(guī)律,獲得了相關(guān)因素與環(huán)形空間凍脹力和凍結(jié)管徑向失穩(wěn)的關(guān)系。數(shù)值計算結(jié)果表明:已凍泥漿的彈性模量、泥漿孔隙率和地層深度為影響環(huán)形空間凍脹力的主要因素,而地層初始水平應(yīng)力為影響凍結(jié)孔內(nèi)壁環(huán)向應(yīng)力的關(guān)鍵因素;具體表現(xiàn)為已凍泥漿彈性模量越大、泥漿孔隙率越大、地層深度越大時未凍泥漿區(qū)凍脹力越大,而地層初始水平應(yīng)力越大時凍結(jié)孔內(nèi)壁環(huán)向應(yīng)力越小。再次,采用自行設(shè)計的試驗裝置進(jìn)行物理模型試驗,對不同規(guī)格凍結(jié)管在不同工況下的凍結(jié)試驗,獲得了環(huán)形空間凍脹力變化規(guī)律和凍結(jié)管徑向失穩(wěn)規(guī)律。試驗結(jié)果表明:凍結(jié)管徑向失穩(wěn)現(xiàn)象可分為加壓、冷縮、凍脹和破壞四個階段,獲得的徑向失穩(wěn)臨界荷載與水壓試驗和數(shù)值模擬結(jié)果相差較小,且失穩(wěn)波數(shù)同特征值屈曲計算模態(tài)圖;有壓凍結(jié)工況時環(huán)形空間產(chǎn)生的凍脹力明顯大于無壓凍結(jié)工況;偏心情況時環(huán)形空間產(chǎn)生的凍脹力略大于理想情況,同一層位不同方位測點(diǎn)受力存在一定不均。最后,綜合上述研究成果,總結(jié)得到,對比凍結(jié)管徑向失穩(wěn)和硬巖內(nèi)側(cè)拉裂的時間點(diǎn),若硬巖拉裂先于凍結(jié)管失穩(wěn),凍結(jié)管處于安全狀態(tài);若凍結(jié)管失穩(wěn)先于硬巖拉裂,則凍結(jié)管破壞。
[Abstract]:In freezing construction, the safety and stability of freezing pipe is the key factor affecting the smooth progress of freezing construction. In recent years, there have been many accidents of freezing pipe diametral instability, flattening and flattening in hard rock formation freezing method, which lead to the failure of freezing project, which has a great influence on the progress and benefit of the project. In view of this phenomenon, the mechanism and law of diametral instability of frozen pipes in hard rock strata are studied comprehensively by means of analytical analysis, numerical simulation and physical simulation. Firstly, a multi-layer mechanics model of "frozen pipe, frozen mud, unfrozen mud and surrounding rock" is established, and the analytical solution of frost heave force in unfrozen mud region is derived, and the relationship between frost heave force in unfrozen area and the thickness of frozen mud wall and the influence factors are obtained. Secondly, based on the simulation of single tube temperature field, single tube radial buckling and rock crack, the numerical calculation of the diametral instability of frozen pipe subjected to frost heave force is carried out. Considering the hydraulic fracturing of surrounding rock, the thickness, frost heave force change and diameter buckling deformation of frozen pipe during freezing process are grasped, and the relationship between relevant factors and frost heave force in annular space and diameter instability of frozen pipe is obtained. The numerical results show that the elastic modulus of frozen mud, mud porosity and formation depth are the main factors affecting the frost heave force in annular space, and the initial horizontal stress is the key factor to influence the circumferential stress of the inner wall of the frozen hole. The concrete performance is that the greater the elastic modulus of frozen mud, the greater the porosity of the slurry, the greater the formation depth, the greater the frost heave force in the unfrozen mud zone, and the smaller the circumferential stress of the inner wall of the frozen hole is when the initial horizontal stress of the formation is greater. Thirdly, the physical model test was carried out by using the self-designed test device, and the freezing test of different specification freezing pipes under different working conditions was carried out, and the variation law of frost heave force in annular space and the radial instability law of freezing pipe were obtained. The experimental results show that the radial instability of frozen pipes can be divided into four stages: compression, cold shrinkage, frost heave and failure, and the difference between the critical radial buckling load and the results of water pressure test and numerical simulation is small. And the instability wave number is the same as the eigenvalue buckling calculation modal diagram; The frost heaving force in annular space under pressure freezing condition is obviously larger than that in non-pressure freezing condition, and the frost heave force in annular space under eccentricity is slightly larger than that in ideal condition. Finally, by synthesizing the above research results, it is concluded that the frozen pipe is in a safe state if the hard rock fracture is prior to the freezing pipe instability, compared with the time points of the diametral instability of the frozen pipe and the inner tensile crack of the hard rock. If the freezing pipe is unstable before the hard rock crack, the freezing pipe will be destroyed.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TD265.3

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