鉆孔灌注擴(kuò)底樁抗拔承載力及耐久性研究
發(fā)布時間：2019-01-30 14:14
【摘要】：鉆孔灌注擴(kuò)底樁是近年發(fā)展起來的一種新的樁型,相比傳統(tǒng)的鉆孔灌注樁具有更高的承載力,已經(jīng)成為大型工程普遍采用的一種基礎(chǔ)形式。隨著大型市政設(shè)施、大跨橋梁、超高層建筑等建(構(gòu))筑物及超大面積的純地下室的建設(shè),近年來鉆孔灌注擴(kuò)底樁在國內(nèi)工程界逐漸得到廣泛應(yīng)用。 目前,對擴(kuò)底樁的理論研究還不完整,擴(kuò)底樁的實(shí)際承載能力都是通過現(xiàn)場荷載試驗(yàn)確定。然而試驗(yàn)不僅花費(fèi)時間長、耗資巨大、代表性差,而且很難測出完整的Q-S曲線。因此有對擴(kuò)底樁的承載性狀進(jìn)行探討的必要性,提出更加符合實(shí)際的擴(kuò)底樁極限承載力的理論計(jì)算方法。另外由于鉆孔灌注擴(kuò)底樁在使用過程中要不斷接觸水和土壤,導(dǎo)致其中的有害物質(zhì)會侵蝕樁體,造成鉆孔灌注擴(kuò)底樁耐久性裂化,并對上部結(jié)構(gòu)產(chǎn)生影響。 本文選用了ANSYS數(shù)值計(jì)算軟件建立了擴(kuò)底樁樁土相互作用模型,對擴(kuò)底樁的受力性狀進(jìn)行了深入細(xì)致的探討和分析。研究的主要內(nèi)容有： (1)論述了鉆孔灌注擴(kuò)底樁的抗拔破壞機(jī)理及現(xiàn)有抗拔承載力計(jì)算方法。 (2)采用平面有限元方法,利用通用有限元軟件ANSYS建立軸對稱分析模型,計(jì)算了不同情況下樁-土的豎向位移,得出了鉆孔灌注擴(kuò)底樁的抗拔極限荷載。 (3)針對沿海環(huán)境,指出了氯鹽環(huán)境下鉆孔灌注擴(kuò)底樁的腐蝕機(jī)理,建立了氯離子在鉆孔灌注擴(kuò)底樁內(nèi)的侵蝕模型和對應(yīng)的耐久性極限狀態(tài),根據(jù)工程參數(shù)提出了相應(yīng)的壽命預(yù)測方法,對不同水灰比、保護(hù)層厚度、暴露區(qū)域的混凝土失效概率進(jìn)行了分析計(jì)算。并針對大部分工程提出了一些加強(qiáng)混凝土抗氯離子侵蝕的措施。 (4)最后針對北方嚴(yán)寒地區(qū)的鉆孔灌注擴(kuò)底樁,論述了其經(jīng)受凍融循環(huán)破壞的機(jī)理和常見損傷破壞形式,提出了一些提高鉆孔灌注擴(kuò)底樁抗凍融循環(huán)損傷的措施。
[Abstract]:Bored cast-in-place reamed pile is a new type of pile developed in recent years. Compared with the traditional bored pile, it has higher bearing capacity and has become a basic form widely used in large-scale projects. With the construction of large municipal facilities, long-span bridges, super-high-rise buildings and super-large area pure basement, bored cast-in-place reaming piles have been widely used in the domestic engineering field in recent years. At present, the theoretical study of reamed pile is not complete, and the actual bearing capacity of belled pile is determined by field load test. However, the test is not only time-consuming, costly and unrepresentative, but also difficult to measure a complete Q-S curve. Therefore, it is necessary to discuss the bearing capacity of reamed pile, and a theoretical calculation method of ultimate bearing capacity of belled pile is put forward. In addition, due to the continuous contact with water and soil during the use of the bored cast-in-place reaming pile, the harmful substances in the pile will erode the pile body, resulting in the durability cracking of the bored cast-in-place reaming pile and the influence on the superstructure. In this paper, the ANSYS numerical calculation software is used to establish the pile-soil interaction model of the reamed pile, and the mechanical behavior of the belled pile is discussed and analyzed in detail. The main contents of the study are as follows: (1) the mechanism of uplift failure of bored cast-in-place reamed pile and the existing calculation methods of uplift bearing capacity are discussed. (2) using the plane finite element method and the general finite element software ANSYS, the axisymmetric analysis model is established, the vertical displacement of pile-soil under different conditions is calculated, and the ultimate uplift load of bored cast-in-place reamed pile is obtained. (3) aiming at the coastal environment, the corrosion mechanism of bored cast-in-place reaming pile under chloride environment is pointed out, and the corrosion model and the corresponding durability limit state of chloride ion in bored cast-in-place reaming pile are established. According to the engineering parameters, the corresponding life prediction method is put forward, and the failure probability of concrete in different water-cement ratio, cover thickness and exposed area is analyzed and calculated. Some measures to strengthen the chloride corrosion resistance of concrete are put forward for most of the projects. (4) at last, aiming at the bored cast-in-place reaming pile in the cold area of northern China, the mechanism and common damage forms of the pile subjected to freeze-thaw cycle are discussed, and some measures to improve the anti-freezing and thawing damage of the bored cast-in-place pile are put forward.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2013
【分類號】：TU473.1
本文編號：2418214
[Abstract]:Bored cast-in-place reamed pile is a new type of pile developed in recent years. Compared with the traditional bored pile, it has higher bearing capacity and has become a basic form widely used in large-scale projects. With the construction of large municipal facilities, long-span bridges, super-high-rise buildings and super-large area pure basement, bored cast-in-place reaming piles have been widely used in the domestic engineering field in recent years. At present, the theoretical study of reamed pile is not complete, and the actual bearing capacity of belled pile is determined by field load test. However, the test is not only time-consuming, costly and unrepresentative, but also difficult to measure a complete Q-S curve. Therefore, it is necessary to discuss the bearing capacity of reamed pile, and a theoretical calculation method of ultimate bearing capacity of belled pile is put forward. In addition, due to the continuous contact with water and soil during the use of the bored cast-in-place reaming pile, the harmful substances in the pile will erode the pile body, resulting in the durability cracking of the bored cast-in-place reaming pile and the influence on the superstructure. In this paper, the ANSYS numerical calculation software is used to establish the pile-soil interaction model of the reamed pile, and the mechanical behavior of the belled pile is discussed and analyzed in detail. The main contents of the study are as follows: (1) the mechanism of uplift failure of bored cast-in-place reamed pile and the existing calculation methods of uplift bearing capacity are discussed. (2) using the plane finite element method and the general finite element software ANSYS, the axisymmetric analysis model is established, the vertical displacement of pile-soil under different conditions is calculated, and the ultimate uplift load of bored cast-in-place reamed pile is obtained. (3) aiming at the coastal environment, the corrosion mechanism of bored cast-in-place reaming pile under chloride environment is pointed out, and the corrosion model and the corresponding durability limit state of chloride ion in bored cast-in-place reaming pile are established. According to the engineering parameters, the corresponding life prediction method is put forward, and the failure probability of concrete in different water-cement ratio, cover thickness and exposed area is analyzed and calculated. Some measures to strengthen the chloride corrosion resistance of concrete are put forward for most of the projects. (4) at last, aiming at the bored cast-in-place reaming pile in the cold area of northern China, the mechanism and common damage forms of the pile subjected to freeze-thaw cycle are discussed, and some measures to improve the anti-freezing and thawing damage of the bored cast-in-place pile are put forward.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2013
【分類號】：TU473.1
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