【作者】 王哲；

【导师】 龚晓南；

【作者基本信息】 浙江大学 ， 岩土工程， 2005， 博士

【摘要】 本文采用解析算法,就考虑土芯作用下的筒桩竖向承载力计算、筒桩在竖向与水平向力同时作用下的性状分析、双排桩海堤筒桩结构内力与位移计算等三个方面展开了较为深入细致的研究。主要工作和研究成果如下: 1.考虑筒桩土芯分担荷载以及筒桩与土芯内摩阻力发挥情况,采用弹塑性荷载传递函数推导出了筒桩的竖向荷载—沉降关系的解析表达式,并计算得到任意截面桩身轴力及内外侧摩阻力的表达式。计算表明:土芯顶端分担的荷载以及筒桩内侧摩阻力随着桩顶荷载、桩土模量比、筒桩内外径比的变化而变化;在单桩荷载—沉降曲线中,l、C_sa和k_a越大,桩顶极限承载力越大,对应桩顶沉降量也越大。 2.在现行m法假设的基础上导出了筒桩单桩在竖向集中荷载、水平向荷载、桩身自重以及桩内外侧摩阻力耦合作用下的计算公式,首次把自由段荷载的作用耦合进来。计算表明:桩身弯矩值和桩身变位随着桩顶轴力P的增大而提高,当基桩自由长度和竖向荷载较大时,P—△效应不可忽略;桩身自重以及桩周内外摩阻力对桩身弯矩和桩身变形的影响很小,数量级在10^-4,计算时可忽略他们其对桩身内力的影响;随着埋入深度的增大,桩身最大弯矩和桩顶水平变位都增大,但是埋入深度增大一定值,桩身弯矩和桩身变位趋于稳定;桩顶水平变位和桩身最大弯矩随着各参数——桩顶弯矩或桩顶水平力、自由长度、桩身弹性模量和水平地基抗力系数、自由段荷载等的增大而增大,其中,桩顶水平力对桩身最大弯矩和桩顶水平变位的影响最大。 3.介绍了几种筒桩海堤的结构型式,并应用结构位移法求解了双排桩海堤各桩的等效桩顶荷载。对桩顶挠度系数、桩顶刚度系数、顶板的位移和转角进行了求解,最后将作用于筒桩海堤的荷载等效至各桩头。 4.计算了施工期荷载作用下单桩受力、海堤施工期短暂作用效应组合以及正常使用下作用效应的持久组合3种工况下的桩身弯矩和桩身水平变位。计算表明:正常使用下作用效应的持久组合工况下靠陆侧桩身有最大值弯矩;施工作用效应的短暂组合工况下靠陆侧桩身弯矩是从桩顶至桩头逐渐衰减的。分析了桩间距B₁、排间距B₂的变化对筒桩海堤荷载传递性状的影响。更多还原

【Abstract】 Construction technics and structure characteristic of large diameter cast-in-situ tubular piles is different from that of ordinary cast-in-place piles or steel pipe piles, which bring on the particularity of tubular pile’s bearing characteristic. Using analytical arithmetic, three aspects have been studied that are tubular pile’s vertical bearing force considering soil core’s function, tubular pile’s bearing characteristic under vertical and transverse load, and stress and displacement of double-row-pile sea wall’s piles. The main original work and results are as follows:1. With elastic-plastic load transfer function, a set of analytical equations for the axial load-settlement curve of cast-in-situ tubular pile have been deduced to determine the vertical bearing capacity of pile according to the settlement of the pile top. The distribution equations of axial force and friction along pile can be gotten. It shows that force soil core beared and friction will change following the pile top load, pile and soil elasticity modulus ratio and pile’s inner and outer diameter ratio. In single pile’s load-settlement curve, the longer pile length is or the bigger C_sa and k_a is, the bigger the ultimate resistance of the pile is, then the bigger the settlement is.2. On the basis of ’m’ method, coupling formulas have been gotten when single pile is loaded under the load combination of vertical focus load, transverse load, pile’s self-weight and its inner and outer friction, and free load is concluded in for the first time. It shows that P-Δ effect can’t be ignored when the free length and vertical load are big, and pile’s deadweight and its friction have little influence on distortion and bending force along pile. The top transverse distortion and the most bending force have the same current with the top bending force, the top transverse force, free length, pile’s diameter, etc, in which the top transverse force has the biggest influence on pile’s most bending force and the top transverse distortion.3. Several kinds of sea wall structures are introduce in this paper, equivalent pile top load of each pile of double-row-pile sea wall was gotten by the method of structure displacement.First pile top distortion coefficient, top rigid coefficient, tip board’ s displacement and its corner are calculated, then the loads acting on the tip of the sea wall are equivalent to each pile top.4. Bending force and transverse distortion along pile are calculated in three kinds of working conditions, which are single pile under load in construction period, fugacious load domino effect combination in sea wall construction period and permanent load domino effect combination in common using period. It shows that pile has the biggest bending force value under the third working condition, bending force decrease along the pile from the pile top under the second working condition. Influence of changes of pile space between and row space between to load transfer characteristic of sea wall is analyzed.更多还原