【摘要】：嵌巖樁作為樁基基礎(chǔ)已經(jīng)廣泛應(yīng)用于高層建筑、大型橋梁、重型廠房等重點工程中,關(guān)于其工作機理的研究頗多,其破壞形式也有多種。例如:嵌巖段樁端巖石剪切與壓屈破壞模式、整體剪切破壞形式、樁巖界面破壞模式等。其應(yīng)用的理論模型也各有不同,并得出了不同的結(jié)果。本文假設(shè)樁體及巖體具有足夠的強度,嵌巖樁的破壞為樁巖界面破壞,采用室內(nèi)模型試驗的方法對嵌巖樁的工作機理展開研究。為達到試驗數(shù)據(jù)能夠反映實際工程的目的,模型試驗的制作工序模擬現(xiàn)場實際工程樁的成樁工序,采用GH-200電子萬能試驗機、WDW-E200D負荷傳感器、DH-3814-4靜態(tài)應(yīng)變測試儀、百分表分別對樁體加載、位移及應(yīng)變進行測試并利用力學(xué)關(guān)系式求出軸力和摩阻力的變化關(guān)系。制作了兩個試件分別進行一次加載和反復(fù)加載試驗進行對比,根據(jù)整理所得數(shù)據(jù)得到如下試驗成果:1)通過試驗發(fā)現(xiàn)樁基在一次加載過程中,荷載-位移曲線可以分為三個不同的變形階段:第Ⅰ階段屬于彈性階段;第Ⅱ階段屬于屈服階段;第Ⅲ階段屬于殘余變形階段。這三個階段反應(yīng)了樁體在整個加載過程中樁頂位移、樁底位移、樁體壓縮量與加載之間的變化關(guān)系;2)在本實驗一次加載和反復(fù)加載過程中,樁身嵌巖段軸力均是自上而下逐漸變小,而且在卸載后存在著部分殘余變形,不可完全回復(fù);3)在一次加載和反復(fù)加載到極限荷載時,樁土界面摩阻力小,樁巖界面摩阻力大。在模擬土體和模擬巖體交界面處摩阻力變化最快,樁體在這個截面的摩阻力為所有截面中最大;4)一次加載和反復(fù)加載均反映出一個共同的問題:隨著樁頂荷載值的變大,力是逐步傳至樁底的,樁身各截面處的摩阻力并不是同步發(fā)揮作用的。樁與土體之間摩阻力先發(fā)揮至最佳,隨后樁與巖體之間的摩阻力發(fā)揮至最佳,當(dāng)樁巖界面即將發(fā)生破壞時,樁體的承載力就達到了極值。
[Abstract]:Rock socketed pile as a pile foundation has been widely used in high-rise buildings, large bridges, heavy plant and other key projects. There are a lot of research on its working mechanism and many kinds of failure forms. For example: rock shear and buckling failure mode, integral shear failure mode, pile rock interface failure mode and so on. The applied theoretical models are different, and different results are obtained. In this paper, it is assumed that the pile body and rock mass have sufficient strength, and the failure of rock-socketed pile is the failure of pile-rock interface. The working mechanism of rock-socketed pile is studied by the method of laboratory model test. In order to achieve the purpose that the test data can reflect the actual project, the production procedure of the model test simulates the piling procedure of the actual engineering pile on the spot, and the static strain tester DH-3814-4 is used in the WDW-E200D load sensor with GH-200 electronic universal testing machine. The load displacement and strain of pile are measured by the dial table and the relationship between axial force and friction resistance is obtained by using the mechanical relation. Two specimens were made to carry out one loading test and the repeated loading test respectively. According to the data collected, the following experimental results were obtained: 1) the pile foundation was found to be in the process of one loading. The load-displacement curve can be divided into three different deformation stages: the first stage belongs to the elastic stage, the second stage belongs to the yield stage, and the third stage belongs to the residual deformation stage. These three stages reflect the relationship between pile top displacement, pile bottom displacement, pile compression and loading during the whole loading process. The axial force of the rock-embedded segment of the pile is gradually reduced from the top to the bottom, and there is some residual deformation after unloading, which can not be fully recovered. 3) when the pile is loaded and repeatedly loaded to the limit load, the friction resistance of the pile-soil interface is small and the frictional resistance of the pile-rock interface is large. At the interface between the simulated soil and the simulated rock mass, the friction resistance of the pile is the largest in all sections. The single loading and repeated loading all reflect a common problem: with the increase of the pile top load, The force is gradually transmitted to the bottom of the pile, and the friction at each cross section of the pile does not act synchronously. The friction resistance between pile and soil is the best, and then the friction between pile and rock is the best. When the interface of pile and rock is about to be destroyed, the bearing capacity of pile reaches the extreme value.
【學(xué)位授予單位】：中北大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU473.1

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