【摘要】：筒型基礎(chǔ)是一種比較常見的海上平臺基礎(chǔ)形式，具有節(jié)約成本和環(huán)保等優(yōu)點(diǎn)，近年來開始被用作海上風(fēng)機(jī)結(jié)構(gòu)基礎(chǔ)。沉放安裝是筒型基礎(chǔ)關(guān)鍵施工過程，也是其實(shí)現(xiàn)工程應(yīng)用的前提，而目前其沉放過程還存在諸多問題。 針對海上風(fēng)機(jī)筒型基礎(chǔ)沉放過程，結(jié)合現(xiàn)有研究和工程中存在的問題，通過模型試驗(yàn)和數(shù)值模擬方法，開展了砂土中筒型基礎(chǔ)沉放過程筒—土作用研究，揭示了筒型基礎(chǔ)靜壓沉放過程中的擠土效應(yīng)、負(fù)壓沉放過程中的減阻效應(yīng)、沉放阻力與滲流特性以及復(fù)合筒型基礎(chǔ)的負(fù)壓沉放與調(diào)平特性，并在此基礎(chǔ)上改進(jìn)了已有沉放阻力和沉放所需負(fù)壓的計算方法。本文主要研究工作和創(chuàng)新成果如下： （1）針對長徑比（L/D）為1.0的傳統(tǒng)筒型基礎(chǔ)結(jié)構(gòu)和長徑比為0.33的寬淺式筒型基礎(chǔ)結(jié)構(gòu)，分別開展了筒型基礎(chǔ)靜壓沉放試驗(yàn)，發(fā)現(xiàn)筒壁下沉過程中存在明顯的擠土效應(yīng)，使得周圍土體應(yīng)力水平大大提高；L/D=1.0基礎(chǔ)還存在土塞效應(yīng)，內(nèi)側(cè)土壓力遠(yuǎn)大于外側(cè)；端阻力在總沉放阻力中起主要作用；已有阻力計算方法不能準(zhǔn)確預(yù)測筒型基礎(chǔ)靜壓貫入阻力。在對試驗(yàn)數(shù)據(jù)分析的基礎(chǔ)上，提出了一種能更準(zhǔn)確地預(yù)測靜壓沉放阻力的、基于靜力觸探試驗(yàn)和靜壓管樁理論的計算方法。 （2）針對目前負(fù)壓沉放存在的問題，利用上述兩個筒型基礎(chǔ)開展了負(fù)壓沉放試驗(yàn)，揭示了負(fù)壓下沉過程中筒壁內(nèi)、外側(cè)摩擦力和端部阻力的變化規(guī)律，發(fā)現(xiàn)負(fù)壓下沉?xí)r內(nèi)側(cè)摩阻力與端阻力大大減小，而外側(cè)摩阻力幾乎不變；現(xiàn)有臨界負(fù)壓是過于保守的，即使施加負(fù)壓超過臨界負(fù)壓值也不會發(fā)生滲透破壞。并揭示了沉放減阻效果與施加負(fù)壓之間的關(guān)系，改進(jìn)了現(xiàn)有沉放所需負(fù)壓計算方法。 （3）針對海上風(fēng)機(jī)復(fù)合筒型基礎(chǔ)這一新型筒型基礎(chǔ)結(jié)構(gòu)，通過數(shù)值模擬和模型試驗(yàn)方法，開展了負(fù)壓沉放與調(diào)平研究，揭示了其沉放和調(diào)平過程中負(fù)壓與滲流特性，以滲流出口水力梯度為控制條件，建立了復(fù)合筒型基礎(chǔ)沉放和調(diào)平臨界負(fù)壓計算公式，發(fā)現(xiàn)復(fù)合筒型基礎(chǔ)沉放所需負(fù)壓略小于未分艙基礎(chǔ)情況；當(dāng)復(fù)合式筒型基礎(chǔ)在沉放過程中發(fā)生傾斜時，可通過抽吸升高艙體氣體實(shí)現(xiàn)快速調(diào)平，且施加調(diào)平負(fù)壓小于臨界負(fù)壓，，在多個艙體內(nèi)施加負(fù)壓調(diào)平可以降低調(diào)平負(fù)壓值。
[Abstract]:Cylindrical foundation is a common offshore platform foundation with the advantages of cost saving and environmental protection. It has been used as the structural foundation of offshore fan in recent years. Sinking installation is the key construction process of cylindrical foundation, and is also the premise of its engineering application. However, there are still many problems in the sinking and laying process. In view of the sinking process of offshore fan tube foundation, combined with the existing research and engineering problems, through the model test and numerical simulation method, the research on the tube-soil interaction during the sinking process of the tube foundation in sand is carried out. The soil squeezing effect, drag reducing effect, sinking resistance and percolation characteristics and the negative pressure sinking and leveling characteristics of the cylindrical foundation during the static pressure sinking and laying are revealed, and the negative pressure sinking and leveling characteristics of the composite cylinder foundation are also revealed. On this basis, the existing calculation method of sinking resistance and negative pressure is improved. The main achievements of this paper are as follows: (1) for the traditional cylindrical foundation with a aspect ratio of 1.0 and the wide-shallow cylindrical foundation with a aspect ratio of 0.33, The static pressure sinking test of cylindrical foundation was carried out, and it was found that there was obvious soil squeezing effect in the process of cylinder wall sinking, which greatly improved the stress level of surrounding soil. There is also soil plug effect in L/D=1.0 foundation, the inner earth pressure is much larger than the outside, the end resistance plays a major role in the total sinking resistance, and the existing resistance calculation method can not accurately predict the static pressure penetration resistance of the cylindrical foundation. Based on the analysis of test data, a calculation method based on static penetration test and static pressure pipe pile theory is proposed, which can predict the static pressure sinking resistance more accurately. (2) in view of the problems existing in the negative pressure sinking at present, the negative pressure sinking test is carried out by using the above two cylinder foundations, which reveals the variation law of the friction force and the end resistance in the inner and outer side of the cylinder wall during the negative pressure sinking. It is found that the inner friction and the end resistance are greatly reduced while the lateral friction is almost unchanged when the negative pressure is sinking. The existing critical negative pressure is too conservative, even if the negative pressure is applied above the critical negative pressure value, there will not be osmotic damage. The relationship between the effect of drag-reduction and the application of negative pressure is revealed, and the existing calculation method of negative pressure is improved. (3) in view of the new type of tubular foundation of offshore fan composite cylinder foundation, through numerical simulation and model test method, the research of negative pressure sinking and leveling is carried out, and the characteristics of negative pressure and seepage in the process of sinking and leveling are revealed. Taking the hydraulic gradient of seepage outlet as the control condition, the formulas of settling and leveling critical negative pressure of composite cylindrical foundation are established. It is found that the negative pressure required for sinking of composite cylindrical foundation is slightly smaller than that of non-subdivision foundation. When the compound cylinder foundation tilts in the process of sinking, it can be quickly leveled by pumping and raising the cabin gas, and the leveling negative pressure is less than the critical negative pressure, and the negative pressure adjustment value can be reduced by applying the negative pressure adjustment in multiple tanks.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TU476

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