【摘要】：海洋樁靴基礎(chǔ)是自升式海上石油和天然氣開發(fā)平臺(tái)的重要組成部分。這種自升式海上開發(fā)平臺(tái)一般安裝在淺海至中等水深的海域。海洋樁靴基礎(chǔ)通常為倒圓錐形,樁靴基礎(chǔ)通常埋入海床土體中深至三倍基礎(chǔ)直徑的深度,以獲得足夠的承載力。雖然有學(xué)者對(duì)樁靴基礎(chǔ)在均質(zhì)土和多層土體中的失效機(jī)理和承載力進(jìn)行了研究,但土體的空間變異性對(duì)樁靴基礎(chǔ)在非均質(zhì)粘土中承載力的影響目前還不清楚。本文通過將隨機(jī)有限元方法和蒙特卡洛模擬理論結(jié)合,發(fā)展了考慮粘土空間變異性時(shí)樁靴基礎(chǔ)(Spudcan)失效機(jī)理和承載力的研究方法。海床土體特性在空間水平、豎直方向都會(huì)變化,本研究中空間變異性是指海床土體的不排水剪切強(qiáng)度的變異性。本文首先闡述了海床土體的隨機(jī)特性,通過隨機(jī)場(chǎng)理論模擬海床土體的空間變異性,并結(jié)合有限元理論研究了海洋樁靴基礎(chǔ)的承載力及失效機(jī)理。樁靴基礎(chǔ)形狀按真實(shí)的基礎(chǔ)形狀簡化后模擬,將模擬結(jié)果與已有文獻(xiàn)進(jìn)行對(duì)比,驗(yàn)證了本研究方法的正確性。結(jié)果表明,樁靴基礎(chǔ)在非均質(zhì)土上的承載力取決于剪切經(jīng)過的路徑大小以及剪切面經(jīng)過的土體不排水剪切強(qiáng)度的高低。隨機(jī)有限元方法結(jié)合蒙特卡洛模擬的方法分析土體水平和豎直方向空間變異性對(duì)海洋樁靴基礎(chǔ)承載力和失效機(jī)理的影響。本文進(jìn)一步研究了土體的各向同性和各向異性對(duì)樁靴基礎(chǔ)的影響,研究結(jié)果顯示隨著土體各向異性的增大,樁靴基礎(chǔ)在非均質(zhì)土上的承載力均值逐漸變小。當(dāng)非均質(zhì)土的水平空間相關(guān)長度為基礎(chǔ)的寬度的三倍時(shí),樁靴基礎(chǔ)的承載力變異系數(shù)隨空間變異性的增加而減小。當(dāng)非均質(zhì)土的豎向相關(guān)長度為3 m時(shí),樁靴基礎(chǔ)的承載力變異系數(shù)隨空間變異性的增大而增加。研究了樁靴基礎(chǔ)在非均質(zhì)土上的安全系數(shù)和失效概率。結(jié)果表明當(dāng)非均質(zhì)土的水平空間相關(guān)長度為基礎(chǔ)的寬度的三倍時(shí),隨空間變異性的增加,靴基礎(chǔ)的失效概率逐漸增大,但對(duì)應(yīng)某一失效概率時(shí)的安全系數(shù)逐漸變小。當(dāng)非均質(zhì)土的豎向相關(guān)長度為3 m時(shí),隨空間變異性的增加,樁靴基礎(chǔ)的失效概率逐漸變小,但對(duì)應(yīng)某一失效概率時(shí)的安全系數(shù)逐漸變大。
[Abstract]:Offshore pile-boots foundation is an important part of self-elevating offshore oil and gas development platform. This self-elevating offshore development platform is generally installed in shallow to medium-depth waters. The pile shoe foundation is usually inverted conical, and the pile shoe foundation is usually buried in the seabed soil to the depth of three times the diameter of the foundation in order to obtain sufficient bearing capacity. Although some scholars have studied the failure mechanism and bearing capacity of pile boot foundation in homogeneous soil and multi-layer soil, the effect of soil spatial variability on the bearing capacity of pile boot foundation in heterogeneous clay is not clear. In this paper, by combining stochastic finite element method with Monte Carlo simulation theory, the (Spudcan) failure mechanism and bearing capacity of pile-boot foundation considering the spatial variability of clay are developed. In this study, the spatial variability refers to the variability of the undrained shear strength of the seabed soil. In this paper, the random characteristics of the seabed soil are described, the spatial variability of the seabed soil is simulated by the random field theory, and the bearing capacity and failure mechanism of the pile boot foundation are studied with the finite element theory. The shape of pile and boot foundation is simplified according to the real foundation shape and the simulation results are compared with the existing literatures to verify the correctness of this method. The results show that the bearing capacity of pile boot foundation on heterogeneous soil depends on the size of the shear path and the undrained shear strength of the soil passing through the shear plane. The influence of horizontal and vertical spatial variability of soil on the bearing capacity and failure mechanism of offshore pile boot foundation is analyzed by means of stochastic finite element method and Monte Carlo simulation. The influence of isotropy and anisotropy of soil on the pile-boot foundation is further studied in this paper. The results show that with the increase of soil anisotropy, the average bearing capacity of the pile-boot foundation decreases gradually in heterogeneous soil. When the horizontal spatial correlation length of the heterogeneous soil is three times the width of the foundation, the coefficient of variation of the bearing capacity of the pile-boot foundation decreases with the increase of the spatial variability. When the vertical correlation length of heterogeneous soil is 3 m, the coefficient of variation of bearing capacity of pile and boot foundation increases with the increase of spatial variability. The safety factor and failure probability of pile-boot foundation in heterogeneous soil are studied. The results show that when the horizontal spatial correlation length of the heterogeneous soil is three times of the base width, the failure probability of the boot foundation increases with the increase of spatial variability, but the safety factor of the boot foundation becomes smaller with the corresponding failure probability. When the vertical correlation length of heterogeneous soil is 3 m, the failure probability of pile-boot foundation becomes smaller with the increase of spatial variability, but the safety factor of the pile and boot foundation increases gradually with a certain failure probability.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU476;P75

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