本文關(guān)鍵詞： 嵌巖樁 混凝土抗壓強(qiáng)度 低應(yīng)變反射波法 MIDAS/GTS NX　出處：《南昌大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

【摘要】：在基巖埋深較淺的地區(qū),通常采用嵌巖樁作為高層建筑、橋梁的基礎(chǔ)工程,因此其嵌巖效果很引人關(guān)注。重要工程的建設(shè)中通常是百分之百的基樁進(jìn)行低應(yīng)變反射波法的檢測,結(jié)合少量鉆芯法分析嵌巖樁的入巖深度和樁底沉渣情況,為工程質(zhì)量總體把關(guān)。問題是當(dāng)前鉆芯法抽取的少量嵌巖樁比較隨意、盲目,而影響低應(yīng)變反射波法的因素比較多,尤其是嵌巖樁的特征增加了檢測復(fù)雜性,導(dǎo)致基樁嵌巖效果的檢測評價(jià)并不如意,需要進(jìn)一步研究探討檢測機(jī)理和方法。本文通過南昌某工程嵌巖樁質(zhì)量檢測活動,經(jīng)過取芯樁的混凝土芯樣抗壓試驗(yàn),發(fā)現(xiàn)不少基樁,同一根樁不同深度部位混凝土抗壓強(qiáng)度差異較大。然而以往在實(shí)際混凝土灌注樁基檢測分析中,對于比較完整的基樁,通常均認(rèn)為沿整個(gè)樁身為均勻材質(zhì)。把檢測信息的變化就認(rèn)為是樁身存在一定的質(zhì)量問題,產(chǎn)生了一定的誤判。因此,為了解樁身混凝土抗壓強(qiáng)度對低應(yīng)變反射應(yīng)力波的影響,特別選取其中5根取芯樁,將樁身混凝土逐米取一組芯樣進(jìn)行混凝土抗壓試驗(yàn),得到這5根樁混凝土抗壓強(qiáng)度的變化情況,并與低應(yīng)變反射應(yīng)力波方法檢測結(jié)果進(jìn)行比較分析。結(jié)果表明,由于該工程樁基施工完成后停工將近一年,樁身混凝土強(qiáng)度基本上達(dá)到極值,沿樁身的混凝土強(qiáng)度有些大大超過28天正�；炷猎O(shè)計(jì)強(qiáng)度,出現(xiàn)了明顯的差異性、隨機(jī)性的情況。而隨著樁身混凝土強(qiáng)度的劇烈變化,低應(yīng)變反射波的反射信號雜波越多,樁底反射信號越不明顯。為了進(jìn)一步了解樁身混凝土抗壓強(qiáng)度等相關(guān)參數(shù)對低應(yīng)變反射應(yīng)力波曲線變化的影響,運(yùn)用有限元分析程序MIDAS/GTS NX建立模擬樁-土振動模型。探討了完整樁在激振力、脈沖寬度、樁頂信號接收點(diǎn)位置、樁長對應(yīng)力反射波時(shí)間-速度曲線的影響;研究了樁身缺陷在擴(kuò)徑與縮徑缺陷長度、半徑大小、缺陷位置因素下,應(yīng)力波時(shí)間-速度曲線變化規(guī)律;探討樁側(cè)土與樁底土彈性模量、容重、泊松比、粘聚力和摩擦角等因素影響下,應(yīng)力波的變化規(guī)律;分析了樁長、樁徑、混凝土標(biāo)號、樁底沉渣厚度參數(shù)變化對應(yīng)力反射波時(shí)間-速度曲線的影響。得到一些有益結(jié)論,加深了各個(gè)因素對于低應(yīng)變反射應(yīng)力波信號影響性質(zhì)和影響程度的理解、認(rèn)識,論證了樁身混凝土變化對低應(yīng)變反射波曲線的復(fù)雜影響。這對于今后指導(dǎo)分析工程樁基檢測與分析評判工作具有比較大的作用。
[Abstract]:In areas with shallow bedrock depth, rock-socketed piles are usually used as foundation works for high-rise buildings and bridges, so the effect of rock-socketed is very interesting. In the construction of important projects, 100% of foundation piles are usually used to detect the low strain reflected wave method. Combined with a small amount of core drilling method, the depth of rock socketed pile and the sediment situation of pile bottom are analyzed. The problem is that a small number of rock-socketed piles extracted by drilling core method are relatively random and blind, but there are many factors that affect the low strain reflection wave method. Especially, the characteristics of rock-socketed pile increase the complexity of detection, which leads to the unsatisfactory testing and evaluation of the rock-socketed effect of the foundation pile, so it is necessary to further study the testing mechanism and method. In this paper, the quality detection of rock-socketed pile in a project in Nanchang is studied. Through the compression test of concrete core sample of cored pile, it is found that there are many foundation piles, and the compressive strength of concrete at different depth of the same pile is quite different. However, in the past, in the testing and analysis of actual concrete cast-in-place pile foundation, for the relatively complete foundation pile, It is generally considered that the pile is a homogeneous material along the whole pile. The change of testing information is regarded as the existence of a certain quality problem in the pile body and a certain misjudgment. Therefore, in order to understand the influence of the compressive strength of the pile body on the low strain reflected stress wave, In particular, five coring piles are selected, and a group of core samples are taken from the pile body concrete to test the compressive strength of the concrete, and the change of compressive strength of the pile concrete is obtained. The results are compared with the results of low strain reflection stress wave method. The results show that the strength of concrete of pile body basically reaches the extreme value because the construction of pile foundation is stopped for nearly one year. Some of the concrete strength along the pile body is much higher than the normal concrete design strength for 28 days, and there are obvious differences and randomness. However, with the violent change of the concrete strength of the pile body, the more clutter of the reflected signal of the low strain reflection wave, The less obvious the reflected signal of pile bottom is, in order to further understand the influence of some related parameters, such as compressive strength of pile body concrete, on the change of low strain reflected stress wave curve, The finite element analysis program MIDAS/GTS NX is used to establish the model of pile-soil vibration. The effects of the excitation force, pulse width, the position of the signal reception point on the top of the pile and the pile length on the time-velocity curve of the stress reflection wave are discussed. The variation law of time-velocity curve of stress wave is studied under the factors of the length, radius and position of the defect, the elastic modulus, bulk density and Poisson's ratio of pile side soil and pile bottom soil are discussed. Under the influence of cohesive force and friction angle, the variation law of stress wave is analyzed, and the influence of pile length, pile diameter, concrete label and sediment thickness on the time-velocity curve of stress reflection wave is analyzed. It has deepened the understanding and understanding of the influence of various factors on the properties and the degree of influence of the low strain reflected stress wave signal. The complex influence of pile concrete variation on the low strain reflection wave curve is demonstrated, which has a great effect on guiding the detection and analysis of pile foundation in the future.
【學(xué)位授予單位】：南昌大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TU473.16

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