桩伴侣（变刚度桩）对直接基础与间接基础的优化研究

发布时间：2018-08-05 09:25

【摘要】：桩伴侣是中国发明专利桩头的箍与带箍的桩(200710160966.1)的俗称：桩头侧而上下一设定高度范围设置一闭合环形箍,箍的内径大于桩头的外径,箍与桩是分开的,桩与桩头的箍通过桩间土和垫层的传力来协同工作,组合成带箍的桩。：因其具有对桩竖向支承刚度简单灵活调整的属性,其专业学术名称为“变刚度桩”。为了深入了解桩伴侣的作用机理和承载性状,本文对该技术进行了初步研究。主要的研究成果、创新和结论包括： (1)人为地将桩土共同受力体的某些环节削弱或增强,可改变共同工作的方式,使承载和沉降性状向预定的方向发展,实现工程上可以接受的较大总体沉降与较小差异沉降和较小工后沉降,从而极大地促进岩土工程的技术进步和经济上的巨大节约。 (2)以相对的深和浅来划分基础类型不尽合理,而用“直接基础”和“间接基础”的表述来划分基础类型更加合理,传统上“深基础”与“浅基础”的表述可以特指基础的埋深或相对埋深；直接基础可简单定义为能够直接将荷载传递到上层天然地基的基础；间接基础也可定义为穿过上部持力层将荷载传递到下部持力层并间接影响上层天然地基的基础。显然,这样一种分类方法同时包含了地基与地基两方面的因素,更客观地反映地基与基础之间之间相互依存、相互影响、相互作用的关系。 (3)“用沉降量换承载力”的等价说法或具体解释是地基承载的良性循环,即“上部荷载增大→压实地基土→地基土性质改善→可以承担更大的荷载→进一步压实地基→地基土性质更加改善→……”，现有研究没有或没有充分考虑作用于滑移线上的附加应力对抵抗剪切滑动的贡献；桩伴侣可减小直接基础发生整体剪切破坏的风险。 (4)选择适宜的滑移线可以将地基承载力问题转化为倾覆问题来研究；有桩伴侣的地基基础非常符合较小刚体位移的“圆弧滑动和向下冲剪”假设,滑移线是以基础底板宽度为直径的一个半圆，圆心位于基础底板的中心,基于莫尔库伦强度理论,以符拉蒙的附加应力解答推导出考虑附加应力和土自重的滑移线上土剪力对基底中心抵抗力矩的解析解，将所有的倾覆力矩归结为等效偏心,得到了评价地基承载力的等效偏心法,与通常的地基承载力的计算方法不同,等效偏心法不仅考虑上体性质、基础宽度、埋深等因素,同时考虑了上部结构的等效偏心来综合计价地基承载力,不同的等效偏心对应不同的地基承载力值,等效偏心越小则承载力越人,经初步对比,不考虑地震等水平荷载形成的等效偏心因素,在静力荷载下太沙基公式的极限承载力所对应的相对等效偏心ΔF/B在0.154左右,而承载力标准值所对应的相对等效偏心ΔF/B在0.188左左右：以等效偏心法分析了桩伴侣“止沉”与“止转”的计算思路,中桩对于“止转”力矩的贡献很小,基桩设置应当重点加强边桩、角桩。 (5)论述了间接基础的缺点；进行了复合桩基优化设计对间接基础改进的局限分析；提出个别安全系数的概念解释和质疑常规变刚度调平“内强外弱”的结果,指出当只有基础底板沉降均匀这唯一的一个控制参数时,间接基础调平只能调整桩下部支承刚度的单一手段是产生变刚度调平优化设计调平的结果不符合常理的重要原因,是用降低个别安个系数为代价换取了基础底板沉降均匀；桩伴侣具有调整桩上部支承刚度的能力,可均匀布桩、甚至局部加强边桩、角桩,增大抵抗整体倾覆的能力,适当调整桩顶与基础底板的距离,即边桩、角桩预留沉降大一些，中桩预留沉降小些就可以实现变刚度调平。 (6)比较分析了桩伴侣的类似技术,桩伴侣具有类似技术的优点，且减震隔震,同时起到向土传递水平力、对桩阻隔水平力的双重作用,并且增大了基础底板的刚度；应用刚性桩复合地基时,应当注意地下室井坑破坏隔震、褥垫层模量影响隔震对其抗弯、抗剪能力较低的桩的水平承载产：生的不利因素,此外,常规采用褥垫层的刚性桩复合地基还存在反力“被平均”、基础既不经济又不安全、“流动补偿”导致垫层流失等缺点 (7)按照有限元收敛准则判断桩伴侣的极限承载力有不同程度的提高,但有限元模拟和现场实测证明伴侣对于按照传统方法判定承载力的无显著影响,桩伴侣承载力的提高依赖于沉降量的增大和土塑性的充分发挥,需要打破土原有的本构关系并建立新的体系,有限无软件本质上难以模拟出现“拐点”的“止沉”曲线,最好的方法还是试验；研究了刚柔桩复合地基静载荷试验时设置伴侣对桩土应力比的影响,设置伴侣后桩顶应力大幅度减小,伴侣附近桩间上的应力大幅度提高,证实伴侣较好地起到了替桩头分担荷载作用,伴侣的作用可解释为由于桩顶向上刺入垫层发生剪胀增大了垫层的内摩擦角,也可以理解为由于伴侣的约束作用增大了桩顶上方垫层上柱受到的被动土压力。 (8)提出了整合复合地基和复合桩基的承载力计算公式并以位移调节装置试验的数据进行了验证,建议复合地基技术规范(征求意见稿)修改为：“仅采用褥垫层技术的刚性桩复合地基中的混凝土桩应采用摩擦型桩,如果有可靠措施能够保证桩上相继同时共同工作时,桩顶与基础底板之间的上或垫层不会发生整体剪切破坏或其他滑移型的破坏,则刚性桩复合地基中的混凝土桩应采用端承效果好的桩型,桩端尽量落在好土层上”；推导了桩伴侣的整体承载力安全系数,只要下部持力层稳定安全系数总能保证大于等于2,表明桩伴侣的安全度在合理的范围内；建议对于不同的抗震设防等级的建筑,采用不同的安全系数：建议用适度的不均匀沉降作为检验建筑工程实体质量的外部荷载,以“抵抗不均匀沉降指数”来衡量建筑工程的施工和设计质量水平；提出“最小配桩率”概念；桩伴侣具有“止沉”的沉降特性,沉降主要由上部地基上的压缩引起,影响深度小的直接原位压板试验得到的极限沉降量与最终沉降量可能会比较接近,可直接作为沉降量预测的依据,提出“整体倾斜”极限状态的概念做为变刚调平“概念设计”的实用方法；应用桩伴侣对某处理基桩缺陷事故案例合理方案进行优化,减薄承台,取消片石找平层,提出一项“桩姐妹”的方案,使作为直接基础的桩能够承受上拔拉力,提出了现浇伴侣的施工方法。 (9)建议将承台与土之间的摩擦力小或地基土约束力差的低承台桩基称为“非典型高承台桩基”,将其从“典型的低承台桩基”中细分出来；当不改变直接基础的属性,有限元数值模拟桩伴侣的改进证实：伴侣是承台向地基土传递水平荷载的可靠媒介,即使承台与土之间摩擦力小,也可大幅度减小基桩的应力和位移，对于桩身范围地基土模量低的“非典型高承台桩基”的水平承载性状也有一定的改善；低承台桩基的水平承载性状本质上取决于桩间上抵抗水平荷载的能力；使用桩伴侣，桩顶与基础底板预留沉降空间就可以将传统的桩基础由间接基础改造为直接基础,有限元数值模拟表明：水平荷载作用下桩身应力大幅度降低；设置伴侣后可取消褥垫层；桩与承台脱离开,更加促进了伴侣作用的发挥：伴侣自身受到的内力较大,且较为复杂；罕遇地震时伴侣可作为耗能构件(?)先牺伴侣
[Abstract]:The pile partner is commonly known as the hoop and stirrup pile (200710160966.1) of China's patent pile head (200710160966.1), which sets up a closed ring hoop in the upper and lower height range of the pile head, and the inner diameter of the hoop is larger than the outer diameter of the pile head. The hoop and the pile are separated from the pile, and the pile and the hoop of the pile head are worked together through the force of the soil and the cushion layer. Because of its simple and flexible adjustment of the vertical bearing stiffness of the pile, the professional academic name is "variable stiffness pile". In order to understand the mechanism of the pile partner and the bearing character, this paper has carried out a preliminary study on this technology. The main research results, innovation and conclusion include:
(1) artificially reducing or strengthening some parts of the pile and soil joint force, can change the way of common work, make the bearing and settlement characters develop to the predetermined direction, realize the larger overall settlement and smaller differential settlement and lower settlement in the engineering, and greatly promote the technological progress and economy of the geotechnical engineering. Great savings.
(2) it is not reasonable to divide the basic type with relative depth and shallow, and the basic type is more reasonable with the expression of "direct base" and "indirect foundation". The traditional expression of "deep foundation" and "shallow foundation" can specifically refer to the buried depth or relative buried depth of the foundation. The direct connection foundation can be simply defined as the ability to transfer the load directly. To the foundation of the upper natural foundation, the indirect foundation can also be defined as the basis of passing the load through the upper force layer to the lower bearing layer and indirectly affecting the upper natural foundation. Obviously, such a classification method includes two aspects of the foundation and the foundation, and more objectively reflect the interdependence between the foundation and the foundation. Mutual influence, interaction.
(3) the equivalent theory of "replacing the bearing capacity with the settlement" or the concrete explanation is the benign cycle of the foundation bearing, that is, "the increase of the upper load, the compaction of the foundation soil, the improvement of the soil properties of the foundation, the greater load, the further compaction of the foundation, and the further improvement of the soil properties of the foundation", the existing research has not or did not fully consider the effect of the existing research. Additional stress on the slip line contributes to the resistance to shear sliding, and pile companions reduce the risk of shear failure of direct foundations.
(4) the choice of the suitable slip line can transform the foundation bearing capacity into the overturning problem. The foundation of a pile partner is very consistent with the "circular slip and down shear" hypothesis of the smaller rigid position movement. The slip line is a semicircle with the width of the base plate as the width, the center of the center and the base of the base plate. The analytic solution of the resistance moment of soil shear force on the base of slip line, which considers the additional stress and soil self weight, is derived by Ramon's additional stress solution. All the overturning moments are attributed to the equivalent eccentricity, and the equivalent eccentricity method for evaluating the bearing capacity of the foundation is obtained, which is different from the usual calculation method of the bearing capacity of the foundation. The effect eccentricity method not only considers the properties of the upper body, the width of the foundation and the depth of the buried depth, but also takes into account the equivalent eccentricity of the superstructure to comprehensively calculate the bearing capacity of the foundation. The different equivalent eccentricity corresponds to the different bearing capacity of the foundation. The smaller the equivalent eccentricity is, the more the bearing capacity is, the more the equivalent eccentricity, the equivalent eccentricity formed by the horizontal load, such as the earthquake, is not considered. The relative equivalent eccentricity Delta F/B corresponding to the ultimate bearing capacity of the Tai Sha based formula under static load is about 0.154, while the relative eccentricity of the standard value of the bearing capacity is about 0.188 left: the equivalent eccentricity method is used to analyze the calculation ideas of the pile companion "stop sinking" and "stop", and the tribute of the pile to the "stop" moment. The foundation pile should be strengthened with side piles and corner piles.
(5) the shortcomings of the indirect foundation are discussed, and the limitation analysis of the optimization design of the composite pile foundation to the improvement of the indirect foundation is carried out. The concept of the individual safety factor is explained and the result of the conventional variable stiffness leveling "internal strong and weak" is questioned. It is pointed out that the indirect foundation leveling is only when the only control parameter of the foundation floor is even settlement is the only control parameter. The single means to adjust the support stiffness at the lower part of the pile is the important reason that the result of the adjustment of the optimization design of the variable stiffness adjustment is not consistent with the normal reason. It is used to reduce the settlement uniformity of the base plate by reducing the coefficient of separate safety. The pile partner has the ability to adjust the supporting rigidity of the upper part of the pile, and can even distribute pile, even local pile pile, angle. Pile, increase the ability to resist the overall overturning, properly adjust the distance between the pile top and the base plate, that is, the side pile, the angular pile is reserved for a large amount of settlement, and the reserved settlement of the middle pile can realize the leveling of the variable stiffness.
(6) the similar technology of pile partner is compared and analyzed. The pile partner has the advantages of similar technology, and the shock absorption and isolation, the double action of the horizontal force to the soil, the double action of the pile blocking the horizontal force, and the stiffness of the base plate; when the rigid pile composite foundation is applied, it should be paid attention to the damage isolation of the basement pit and the influence of the cushion modulus. The horizontal bearing capacity of the piles with low bending and shear resistance is the adverse factors of birth. In addition, the rigid pile composite foundation with the conventional cushion has a "average" reaction, and the foundation is neither economical nor safe, and the "flow compensation" leads to the loss of the cushion.
(7) according to the finite element convergence criterion, the ultimate bearing capacity of the pile partner is improved to a different degree. However, the finite element simulation and the field measurement prove that the partner has no significant influence on the bearing capacity according to the traditional method. The increase of the bearing capacity of the pile partner depends on the increase of the settlement and the full play of the soil plasticity. It is difficult to simulate the "sink" curve of "turning point" in the nature of limited software. The best method or test is the best method. The influence of the companion on the stress ratio of the pile and soil is set up when the static load test of the rigid flexible pile composite foundation is set up. The stress of the pile top is greatly reduced after setting up the companion, and the pile on the pile near the companion should be found. It is proved that the partner is better to share the load for the pile head. The role of the partner can be explained by the expansion of the inner friction angle of the cushion because of the rising of the pile top to the cushion. It can also be understood as the increase of the passive earth pressure on the upper column above the top of the pile top because of the binding effect of the companion.
(8) a formula for calculating the bearing capacity of a composite foundation and a composite pile foundation is proposed and verified by the data of the displacement regulator test. It is suggested that the composite foundation technical specification (solicit draft) be modified as: "a friction pile should be used for a mixed soil pile in a rigid pile composite foundation with the cushion layer technology only, if there is a reliable measure." When the pile is working together at the same time, the upper or cushion between the pile top and the base floor will not have the whole shear failure or other slip type failure, then the concrete pile in the rigid pile composite foundation should adopt the pile with good end bearing effect, the pile end falls on the good soil layer as far as possible, and the overall bearing capacity of the pile partner is deduced. The coefficient, as long as the stability safety factor of the lower bearing layer is guaranteed to be greater than 2, indicates that the safety degree of the pile partner is within a reasonable range; it is suggested that different safety factors be adopted for different seismic fortification levels, which suggest that moderate uneven settlement should be used as the external load to test the solid mass of the construction engineering, to "resist" The uneven settlement index is used to measure the construction and design quality of construction projects, and the concept of "minimum pile ratio" is proposed. The settlement characteristics of the pile partner have "subsidence", and the settlement is mainly caused by the compression on the upper foundation. The limit settlement obtained by the direct in situ pressure plate test with small depth may be compared with the final settlement. As the basis of the settlement prediction, the concept of "overall tilt" limit state is put forward as a practical method of "conceptual design" of variable leveling, and the application of pile partners to optimize a reasonable scheme for a case dealing with pile defects, thinning the bearing platform, canceling the Shi Zhaoping layer and putting forward a "pile sister" scheme, As a direct foundation pile, it can bear uplift force, and puts forward the construction method of cast-in-situ companion.
(9) it is suggested that the low bearing pile foundation, which has small friction force between the soil and the soil, is called "atypical high bearing pile foundation", which is subdivided from "typical low bearing pile foundation". When the property of the direct base is not changed, the improvement of the finite element numerical simulation pile companion confirms that the companion is the carrier to transfer water to the foundation soil. The reliable medium of flat load can greatly reduce the stress and displacement of the pile, even if the friction between the pile cap and the soil is small. It also improves the horizontal bearing capacity of the "atypical high platform pile foundation" with the low soil modulus of the pile body, and the horizontal bearing behavior of the low pile foundation is essentially dependent on the resistance level of the pile. Load capacity, the use of pile partners, pile top and foundation floor reserved settlement space can transform the traditional pile foundation from indirect foundation to direct base. Finite element numerical simulation shows that the stress of pile body is greatly reduced under horizontal load; the cushion layer can be cancelled after setting up partner; pile and pile cap are removed from the pile. The role of couples: partners themselves are subject to greater internal forces, and more complex; in rare earthquakes, couples can be used as energy dissipation components (?) First Spouse
【学位授予单位】：太原理工大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU473.1

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