發(fā)布時(shí)間：2018-06-25 20:06

  本文選題：大直徑超長樁 + 溜樁　； 參考：《天津大學(xué)》2015年博士論文

【摘要】：隨著海洋開發(fā)向較深水域拓展,海上采油平臺(tái)需要采用大直徑(直徑2m以上)、超長(入土深度100m以上)的樁基。由于樁和錘重量很大,在沉樁過程中經(jīng)常會(huì)發(fā)生樁體無需錘擊而自由下沉的現(xiàn)象,稱為溜樁。溜樁的發(fā)生輕則會(huì)沖斷定位的鋼絲繩,使得樁和錘損壞;重則造成樁錘滑落大海,或斷樁等重大事故。目前國內(nèi)外對(duì)這方面的研究還比較少。本文在研究溜樁機(jī)理的基礎(chǔ)上,以極限平衡理論、能量守恒理論、擴(kuò)孔理論等理論為依據(jù),提出了判斷沉樁過程中產(chǎn)生溜樁的條件和判斷溜樁區(qū)間的計(jì)算方法。理論計(jì)算的準(zhǔn)確性取決于地基土在沉樁過程中的性態(tài)參數(shù)取值的合理性,為此本文通過室內(nèi)試驗(yàn)和現(xiàn)場實(shí)測數(shù)據(jù)分析,對(duì)沉樁過程中地基土體中孔隙水壓力的發(fā)展及其對(duì)沉樁阻力的影響、樁-土界面土體的疲勞特性等問題進(jìn)行了較為深入的研究,為溜樁分析的參數(shù)選取提供了依據(jù)。同時(shí),對(duì)于沉樁過程中發(fā)生過溜樁現(xiàn)象的樁基的承載力的評(píng)估是工程界最關(guān)心的問題,本文通過對(duì)打樁過程中和打樁后地基土體中的超孔隙水壓力的產(chǎn)生和消散的規(guī)律的研究,從而分析了樁基承載力的時(shí)效性。本文的主要研究內(nèi)容及特色可概括如下:1、本文綜合動(dòng)態(tài)極限平衡原理和利用CAPWAP打樁分析方法對(duì)動(dòng)測實(shí)驗(yàn)數(shù)據(jù)進(jìn)行反分析,揭示了溜樁現(xiàn)象發(fā)生的機(jī)理。在研究溜樁機(jī)理的基礎(chǔ)上,以極限平衡理論、能量守恒理論、擴(kuò)孔理論等理論為依據(jù),提出了判斷沉樁過程中產(chǎn)生溜樁的條件和判斷溜樁區(qū)間的計(jì)算方法。2、樁基貫入過程中沉樁阻力的計(jì)算對(duì)溜樁區(qū)間判斷有著極為重要的作用。目前普遍采用的API規(guī)范提出的土阻力計(jì)算方法,用于設(shè)計(jì)階段的樁基承載力計(jì)算則偏于安全,但是用于評(píng)估溜樁區(qū)間計(jì)算時(shí),則誤差很大且偏于危險(xiǎn)。本文提出的方法考慮了邊載效應(yīng)和動(dòng)力效應(yīng);分別針對(duì)無黏性土與黏土提出了合理的的靜樁端阻力與靜樁側(cè)摩阻力計(jì)算方法;引入了靈敏度概念提出無黏性土與黏性土的動(dòng)側(cè)摩阻力折減因子,因此計(jì)算的溜樁區(qū)間更為合理。3、靜力觸探原位測試方法是獲得土性參數(shù)較為準(zhǔn)確的方法。根據(jù)大直徑超長樁的沉樁特性,提出了根據(jù)靜力觸探實(shí)測數(shù)據(jù)分析動(dòng)樁端阻力與動(dòng)樁側(cè)摩阻力的方法;提出計(jì)算樁端阻力的影響范圍與樁側(cè)摩阻力折減因子沿樁身的的分布;結(jié)合有限元分析比較黏性土中不同錐頭阻力系數(shù)的計(jì)算結(jié)果;據(jù)此提出了適合黏性土端阻力計(jì)算的錐頭阻力系數(shù),建立了應(yīng)用原位測試數(shù)據(jù)計(jì)算沉樁阻力的方法。4、超長樁樁側(cè)摩阻力對(duì)樁基承載力的貢獻(xiàn)是主要的。通過研制大型直剪儀來研究樁與土體的摩擦特性,總結(jié)不同顆粒粒徑砂土與軟黏土在不同密度下的糙度變化,提出工程中適合的使用值;由于樁身下沉過程類似一個(gè)持續(xù)剪切的過程,應(yīng)用環(huán)剪儀對(duì)典型砂土、粉質(zhì)黏土與黏土進(jìn)行大變形殘余強(qiáng)度的試驗(yàn),并分析了不同剪切速度、循環(huán)荷載與黏粒含量等因素對(duì)殘余強(qiáng)度的影響。對(duì)樁土的摩擦特性做了較為充分的總結(jié)。5、國內(nèi)外針對(duì)打樁過程中產(chǎn)生超孔壓對(duì)樁側(cè)摩阻力的影響的研究較少,而大直徑超長樁沉樁過程中樁側(cè)摩阻力的大幅度折減與超孔隙數(shù)壓力的產(chǎn)生有著密切的關(guān)系。本文將現(xiàn)場孔壓監(jiān)測試驗(yàn)數(shù)據(jù)與應(yīng)用劍橋模型的擴(kuò)孔理論相結(jié)合,建立了打樁過程中產(chǎn)生和消散的規(guī)律,據(jù)此研究了樁基承載力的時(shí)效性。6、以荔灣3-1導(dǎo)管架平臺(tái)工程與麗水項(xiàng)目為例,應(yīng)用提出的理論與方法對(duì)平臺(tái)樁基的沉樁過程進(jìn)行了分析研究,計(jì)算得到的自由入泥深度與溜樁區(qū)間與實(shí)測值吻合。
[Abstract]:With the development of marine development to the deeper waters, the offshore oil production platform needs to adopt the pile foundation with large diameter (more than 2m diameter) and super length (above the depth of 100m). Due to the large weight of the pile and the hammer, the pile body is often free from sinking without hammering during the pile sinking process. It is called the slide pile. In this paper, based on the theory of the limit equilibrium, the conservation of energy and the theory of reaming, the condition of judging the pile driving in the process of pile sinking is put forward. The accuracy of theoretical calculation depends on the reasonableness of the values of the parameters of the ground soil in the pile sinking process. Therefore, the development of the pore water pressure in the foundation soil and the influence on the resistance of the pile in the foundation soil and the fatigue of the soil of the pile soil interface in the process of pile sinking are analyzed by the indoor test and the field measured data. In addition, the evaluation of the bearing capacity of pile foundation in the process of pile sinking is the most important problem in the engineering field. The study of the regularity of the dispersion has been carried out to analyze the timeliness of the bearing capacity of the pile foundation. The main contents and characteristics of this paper can be summarized as follows: 1, in this paper, the principle of dynamic limit equilibrium and the reverse analysis of the dynamic test data by using the CAPWAP pile analysis method have been carried out to reveal the mechanism of the occurrence of the slide pile. Based on the theory of limit equilibrium, conservation of energy and the theory of enlargement, the condition of judging the pile driving in the process of pile sinking and the calculation method of calculating the interval of the slide pile.2 are put forward. The calculation of the resistance of the sinking pile in the process of the penetration of the pile foundation is very important for the judgement of the interval of the slide pile. The soil resistance proposed by the commonly used API standard is currently used. Calculation method, the calculation of the bearing capacity of the pile foundation used in the design stage is partial to safety, but the error is very large and dangerous when it is used to evaluate the interval calculation of the slide pile. The method proposed in this paper takes the side effect and the dynamic effect into consideration, and the calculation side of the static pile end resistance and the side friction resistance of the static pile is put forward respectively for the unviscous soil and clay. With the introduction of the concept of sensitivity, the dynamic side friction reduction factor of cohesionless soil and cohesive soil is introduced, so the calculation of the sliding pile section is more reasonable.3. The method of static cone penetration in situ test is a more accurate method to obtain soil parameters. According to the pile characteristics of the large diameter and super long pile, the analysis of the pile end according to the measured data of static cone penetration is proposed. The method of resistance and frictional resistance of pile side is put forward, the influence range of pile end resistance and the distribution of pile side friction reduction factor along the pile body are calculated, and the calculation results of the resistance coefficient of different cone heads in clay soil are compared with the finite element analysis. Accordingly, the resistance coefficient of the cone head suitable for the viscous soil end resistance meter is put forward, and the application in situ measurement is established. The test data to calculate the resistance of pile sinking.4, the contribution of the lateral friction resistance to the bearing capacity of the pile foundation is main. Through the development of a large direct shear apparatus, the friction characteristics of pile and soil are studied, and the roughness changes of different particle size sand soil and soft clay under different density are summarized, and the suitable use value in the project is put forward, because the pile body is sinking over. The process is similar to a continuous shear process. The residual strength of typical sand, silty clay and clay is tested by the ring shear apparatus, and the effects of different shear velocity, cyclic loading and clay content on the residual strength are analyzed. The friction characteristics of the pile and soil are fully summarized.5, the pile driving process at home and abroad is made. There is little research on the effect of the excess pore pressure on the side friction resistance of the pile, and the large reduction of the friction resistance in the large diameter and super long pile is closely related to the generation of the excess pore number pressure. In this paper, the field pressure monitoring test data is combined with the theory of the expansion of the Cambridge model to establish the pile driving process. According to the law and the law of dissipation, the aging.6 of the bearing capacity of the pile foundation is studied. Taking the Liwan 3-1 jacket platform project and the Lishui project as an example, the pile sinking process of the platform pile foundation is analyzed and studied by the proposed theory and method. The calculated free mud depth is consistent with the measured value.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：P751;TE951;TU473.1

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