本文選題：港口與海洋工程 + 淺基礎(chǔ)��； 參考：《天津大學》2016年博士論文

【摘要】：由于復雜的自然環(huán)境和工作條件,離岸淺基礎(chǔ)處于豎向、水平、力矩和扭矩等多種荷載聯(lián)合作用的復合加載條件下。其破壞模式通常包括豎向整體剪切破壞,滑移破壞和傾覆破壞。在傳統(tǒng)的承載力計算理論中,淺基礎(chǔ)在復合加載條件下的承載力是通過修正作用于均勻塑性半無限地基上的條形表面基礎(chǔ)的豎向承載力而得到的。近些年發(fā)展起來的破壞包絡(luò)面方法克服了傳統(tǒng)理論中的諸多不足,能顯式地考慮荷載傾斜,荷載偏心,基礎(chǔ)形狀與埋深,以及地基強度不均勻程度等因素對淺基礎(chǔ)承載力的影響。淺基礎(chǔ)承載力的破壞包絡(luò)面理論在離岸淺基礎(chǔ)的設(shè)計中已獲得了廣泛的應(yīng)用,但由于破壞包絡(luò)面形狀的影響因素眾多,該理論尚待進一步地完善�；诖�,本文首先結(jié)合工程實例討論了破壞包絡(luò)面理論應(yīng)用于工程實踐需要注意的問題,然后通過建立有限元模型確定了一系列邊界條件下的淺基礎(chǔ)的破壞包絡(luò)面方程。本文的研究目的在于完善淺基礎(chǔ)的破壞包絡(luò)面理論,為離岸淺基礎(chǔ)的設(shè)計優(yōu)化提供理論指導。本文的主要研究內(nèi)容和結(jié)論如下:(1)基于破壞包絡(luò)面理論,建立了砂基上四腿平臺多基礎(chǔ)系統(tǒng)的承載力計算方法,并通過工程實例驗證了計算方法的可行性,并對破壞包絡(luò)面理論在計算荷載安全系數(shù)和結(jié)合“分項系數(shù)”法進行基礎(chǔ)設(shè)計等方面的應(yīng)用給出了建議。(2)提出了無拉力土-基礎(chǔ)接觸面的數(shù)值模擬方法。通過與已有研究結(jié)果的對比和相關(guān)試驗的驗證,證明了無拉力土-基礎(chǔ)接觸面可以采用摩擦角接近90°的Coulomb摩擦接觸模型模擬。在此基礎(chǔ)上,研究了平面V-H-M加載模式下無拉力接觸面條形和圓形表面基礎(chǔ)的承載力特性。(3)以破壞包絡(luò)面的形式研究了極復雜荷載條件下無限拉力接觸面表面圓形基礎(chǔ)和不同寬長比矩形防沉板基礎(chǔ)的承載力特性,并在全三維加載條件下,研究了接觸面條件對海底防沉板基礎(chǔ)承載力的影響。(4)一般情況下,傳統(tǒng)方法得到的解都低估了無拉力接觸面條件下得出的有限元解。在包含力矩荷載的復合加載情況下,無拉力接觸面條件下的破壞包絡(luò)線會落在無限拉力接觸面條件下的破壞包絡(luò)線的內(nèi)側(cè)。(5)隨著扭矩荷載的增大,H-M破壞包絡(luò)線成比例地向內(nèi)收縮,即扭矩荷載能有效地減小包絡(luò)線的尺寸,但對其形狀的影響可忽略不計。所以,可分別根據(jù)H-T和M-T間的相互關(guān)系,通過減小用于歸一化的最大水平和力矩荷載的方式縮小H-M破壞包絡(luò)線的尺寸,達到考慮扭矩荷載效應(yīng)的目的。(6)本文提供了所有破壞包絡(luò)線相對應(yīng)的破壞包絡(luò)線方程,并通過計算實例說明如何將所提方程應(yīng)用于巖土設(shè)計。破壞包絡(luò)線方程能夠方便地編入自動計算工具中,快速地生成破壞包絡(luò)線,輔助港口與海洋工程中淺基礎(chǔ)的設(shè)計和優(yōu)化工作。
[Abstract]:Because of the complex natural environment and working conditions, the offshore shallow foundation is under the combination of vertical, horizontal, torque and torque loads. The failure modes usually include vertical whole shear failure, slip failure and overturning failure. In the traditional theory of bearing capacity calculation, the bearing capacity of shallow foundation under composite loading is obtained by modifying the vertical bearing capacity of strip surface foundation acting on uniform plastic semi-infinite foundation. The damage envelope method developed in recent years overcomes many shortcomings in traditional theory and can explicitly consider load tilt, load eccentricity, foundation shape and depth. And the influence of the uneven strength of foundation on the bearing capacity of shallow foundation. The theory of failure envelope of shallow foundation bearing capacity has been widely used in the design of offshore shallow foundation. However, due to many factors affecting the shape of damage envelope, the theory needs to be further improved. Based on this, this paper first discusses the problems needing attention in the application of failure envelope theory in engineering practice with engineering examples, and then establishes a finite element model to determine the damage envelope equation of shallow foundation under a series of boundary conditions. The purpose of this paper is to perfect the theory of damage envelope of shallow foundation and to provide theoretical guidance for the design optimization of offshore shallow foundation. The main contents and conclusions of this paper are as follows: (1) based on the theory of destructive envelope surface, a method for calculating the bearing capacity of a multi-foundation system of four-legged platform on sand foundation is established, and the feasibility of the calculation method is verified by an engineering example. The application of the failure envelope theory to the calculation of load safety factor and to the foundation design with the method of "sub-factor" is also given. A numerical simulation method of tensionless soil-foundation interface is proposed. It is proved that the Coulomb friction contact model with friction angle close to 90 擄can be used to simulate the non-tension soil-foundation contact surface by comparing with the existing research results and verifying the related tests. On this basis, The bearing capacity characteristics of strip and circular surface foundation of tension free contact surface under plane V-H-M loading mode are studied. The surface circular foundation and different widths of infinite tension contact surface under extremely complex loads are studied in the form of failure envelope surface. Bearing capacity characteristics of rectangular anti-sinking plate foundation with length ratio, Under the condition of full three-dimensional loading, the influence of contact surface condition on the bearing capacity of submarine anti-sinking plate foundation is studied. In general, the solutions obtained by the traditional method underestimate the finite element solution obtained under the condition of non-tension contact surface. In the case of a composite load containing a moment load, Under the condition of non-tension contact surface, the failure envelope will fall on the inner side of the failure envelope under the condition of infinite tension contact surface.) with the increase of torque load, the damage envelope line will shrink proportionally inward. The torque load can effectively reduce the size of the envelope, but the influence on the shape of the envelope is negligible. Therefore, according to the relationship between H-T and M-T, the size of H-M damage envelope can be reduced by reducing the maximum horizontal and torque load for normalization. In this paper, all the failure envelope equations corresponding to the failure envelope are provided, and the calculation examples are given to illustrate how to apply the proposed equation to geotechnical design. The damage envelope equation can be easily programmed into the automatic calculation tool to generate the damage envelope quickly, which can assist the design and optimization of shallow foundation in port and ocean engineering.
【學位授予單位】：天津大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：U655.54

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