本文關鍵詞：靜鉆根植樁承載性能的試驗研究以及數(shù)值分析　出處：《浙江大學》2015年博士論文　論文類型：學位論文

  更多相關文章： 靜鉆根植樁 靜荷載試驗 圓孔擴張理論 厚壁圓筒理論 有限元 彈性模量 截面抗壓剛度 承載力預測 正交試驗 豎向抗壓 水平向承載

【摘要】：靜鉆根植樁是一種由水泥土攪拌樁和高強預應力混凝土管樁復合而成的基樁,具有高承載力、適應性強、施工難度低、噪音小、泥漿污染少等優(yōu)點。本文綜述了水泥土、管樁、復合樁、靜鉆根植樁的發(fā)展簡況,重點研究靜鉆根植樁的豎向抗壓承載性能,對水平承載也作了一定的試驗觀察。通過兩處原位靜荷載試驗和一處模型試驗展開研究。原位試驗一進行了多樁對比,原位試驗二通過樁身埋設應變傳感器深入了解靜鉆根植樁的荷載傳遞特性,模型試驗通過消除樁端阻力來研究不同樁型在樁土接觸面上的荷載傳遞差異。由于試驗一除了豎向抗壓還需做水平靜荷載,不能壓至破壞,試驗二雖壓至破壞,但卻是樁頭壓碎而非土層達到極限,所以都未測得理想的極限承載力。為此用兩種預測極限承載力的方法作了預測,彌補試驗的不足。以圓孔擴張理論計算靜鉆根植樁的擠土效應,并與實測值對比,發(fā)現(xiàn)樁上部吻合得較好,下部則是錯誤的,原因是上部土層壓縮性比較高并且對樁孔產(chǎn)生的圍壓比較小,所以能產(chǎn)生擠土效應,并使這部分土層中的樁側(cè)摩阻力得到提高；下部土層壓縮性又低圍壓又大,擠土效應難以實現(xiàn)。以彈性力學厚壁圓筒理論結(jié)合變形協(xié)調(diào)條件對靜鉆根植樁內(nèi)、外部接觸面進行分析,認為滿足一定的條件后樁土界面是最薄弱面,芯樁與水泥土的接觸面不會比之先破壞。圍箍效應可以忽略不計,按內(nèi)芯、芯樁、外殼單獨作用的簡單疊加來計算整樁的強度、剛度、承載力等。借助數(shù)值分析方法補充和完善了原位試驗的不足,得出水泥土內(nèi)芯和外殼的軸力、應力變化,發(fā)現(xiàn)即使長樁以側(cè)摩阻力為主端阻力很小,樁端部位仍需要特別加強。除此之外,當整樁外徑一定時,水泥土外殼厚度越厚(即芯樁外徑越小),整樁承載力越低。水泥土對整樁的截面抗壓剛度貢獻不大,所以能確保其在設計荷載下不被壓碎即可,無需投入額外的成本提高水泥土的摻入比。用有限元結(jié)合正交試驗的方法針對芯樁直徑、壁厚、混凝土強度、水泥土強度展開影響因素分析,發(fā)現(xiàn)芯樁直徑對靜鉆根植樁的抗壓極限承載力、樁側(cè)摩阻力以及樁端阻力的影響最為顯著,是靜鉆根植樁最重要的參數(shù)。芯樁直徑一定后,壁厚對樁側(cè)摩阻力的影響很大,摩擦型樁應優(yōu)先選用厚壁芯樁；水泥土強度對樁端阻力的影響很大,端承型樁應注意提高水泥土的強度。對靜鉆根植長樁優(yōu)化設計的建議是,選用大直徑芯樁,芯樁直徑以略小于鉆孔直徑為宜,且芯樁壁宜厚。又提出一種預測長樁承載力的方法：如果知道某兩種樁徑的樁在相同沉降時的承載力,以及其中一種樁徑的端承比,就可以推斷其它樁徑的樁在相同沉降時的承載力和端承比,進而求得端阻力和側(cè)摩阻力。這里所指的承載力并非僅限于極限承載力,而可以是任意加載階段的承載力。最后通過多樁水平靜荷載試驗對比了靜鉆根植樁和鉆孔灌注樁的水平承載性能,分析各自的受力特點,認為就減小側(cè)向變形量而言,優(yōu)選樁型是鉆孔灌注樁,宜將靜鉆根植樁改為同直徑的鉆孔灌注樁而不宜單純擴大靜鉆根植樁的樁徑。但如果更重視變形恢復能力,優(yōu)選樁型是靜鉆根植樁。
[Abstract]:The static drill rooted pile is a pile of high strength prestressed concrete pipe pile and compounded by soil cement with high bearing capacity, strong adaptability, low construction difficulty, low noise, less mud pollution. This paper reviews the cement soil pile, composite pile, static pile drilling development rooted in the key study on the static drill rooted pile vertical compressive bearing capacity of horizontal load, were also studied in some experiments. By two in-situ static load test and a model test study. In situ test of a multi pile in situ test by comparison, two pile embedded strain sensor understanding static load pile ground drill transfer characteristics, model test of pile load transfer by eliminating the difference of end resistance to study different types of pile in the pile soil contact surface. The test is required in addition to vertical compressive static load level, not pressure to damage, although two test The pressure to destruction, but the pile head crushed rather than soil reached the limit, the ultimate bearing capacity are not so ideal. This is measured by two methods to predict the ultimate bearing capacity is forecasted, make up the deficiency. The theory of cavity expansion calculation of the static drill rooted soil compaction effect of pile, and compare with the measured value the upper part of pile, found good agreement, while the lower part is wrong, the reason is the confining pressure is relatively small and relatively high compressibility of the upper soil layer of pile hole, so can produce the effect of soil compaction, and the friction of the pile side soil in this part is improved; the lower soil compressibility and low confining pressure and high it is difficult to achieve, squeezing effect. Based on the elastic theory of thick wall cylinder with coordinated deformation condition of the static drill rooted in the pile, analyzes the external contact surface that satisfies certain conditions after the pile-soil interface is the weakest surface, core pile and cement soil contact surface is no less than The first destroyed. The hooping effect can be neglected in the inner core, core pile, simple superposition shell alone to calculate the pile strength, stiffness, bearing capacity and so on. With the help of supplement and perfect the lack of in situ test numerical analysis method, the axial force of soil cement in core and shell, stress change, found that even with long pile side friction based end resistance is very small, the pile end parts still need to strengthen. In addition, when the pile diameter is constant, the thickness of the cement shell (i.e. core pile diameter smaller), the pile bearing capacity is low. Large surface compressive stiffness with cement soil on the pile section, so can ensure that it is not to be crushed under the design load, without the need to invest additional cost and improve the soil cement mixing ratio. Using the finite element method combined with orthogonal test for core pile diameter, wall thickness, concrete strength, strength of cement soil to analyze influence factors, find the core The diameter of the pile bearing capacity of compressive ultimate static drill rooted pile, influence of tip resistance of pile side friction and the pile is the most significant, is the most important parameter of the static drill rooted pile. The pile core diameter, wall thickness has great influence on the frictional resistance of the friction pile core pile of thick wall should be preferred the strength of cement soil pile; the influence of tip resistance, end bearing pile should pay attention to improve the strength of cement soil. The static drill rooted long pile optimization design is proposed, using large diameter core pile, pile core diameter to slightly less than the hole diameter is appropriate, and the core pile wall should be thick and proposes a method. A prediction of long pile bearing capacity: if you know a two diameter piles in the same settlement when the bearing capacity, and one of the end bearing pile diameter ratio, it can be concluded that the other diameter piles in the same settlement and bearing capacity of end bearing ratio, and tip resistance and friction resistance are obtained referred to here. The bearing capacity is not only the ultimate bearing capacity and bearing capacity can be arbitrary loading stage. The pile horizontal static load test comparison of the static drill rooted pile and bored pile horizontal bearing performance, analysis of the stress characteristics that reduce the lateral deformation, pile type selection is bored pile should be changed into the static drill rooted pile bored pile with diameter not only expand the static drill rooted pile diameter. But if more deformation restoring capacity, pile type selection is the static drill rooted pile.

【學位授予單位】：浙江大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TU473.1

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