本文選題：大比尺 + 鋼管樁　； 參考：《山東建筑大學(xué)》2017年碩士論文

【摘要】：隨著我國城鎮(zhèn)化進(jìn)程不斷推進(jìn),許多既有建筑物因缺少地下停車場等設(shè)施,其使用功能上的缺陷日益凸顯出來,既有建筑地下空間的開發(fā)和利用越來越引起人們的重視。既有建筑地下增層時(shí),需要先利用原有的樁基或者設(shè)置新的樁基承擔(dān)既有建筑物的荷載,然后開挖土方,增設(shè)地下室。在開挖樁周土過程中,樁基穩(wěn)定性會明顯降低。鋼管樁基礎(chǔ)是最常用的樁基形式之一,通過大比尺模型試驗(yàn)的方法研究鋼管樁的穩(wěn)定性具有十分重要的意義。為了能夠順利開展模型試驗(yàn),設(shè)計(jì)并制作了2.5m×2.5m×3.0m土工模型箱。它由四周圍起的豎向鋼板和外圍通過螺栓相連的水平箍組成。模型箱四個(gè)大角上的角鋼與相鄰的豎立鋼板通過螺栓固定后,可形成模型箱的“臨時(shí)骨架”,同時(shí)防止箱內(nèi)裝滿的土體沿兩鋼板接縫處泄漏。提出了模型箱的豎向鋼板、水平箍和連接螺栓的設(shè)計(jì)方法,并通過一個(gè)實(shí)例介紹了模型箱的設(shè)計(jì)過程。本文針對土體為中砂的情況,對大比尺鋼管樁樁周土開挖條件下的樁身穩(wěn)定性問題進(jìn)行了試驗(yàn)研究。通過模型實(shí)驗(yàn),(1)研究了樁周土在不同開挖比條件下樁身以及支撐的荷載-應(yīng)變變化規(guī)律;(2)通過改變鋼管樁的回轉(zhuǎn)半徑、偏心距、支撐位置、支撐數(shù)目、支撐剛度、開挖比等因素,得到樁身屈曲極限荷載,分析不同因素對樁身穩(wěn)定性的影響;(3)驗(yàn)證課題組提出的虛擬嵌固點(diǎn)法理論在大比尺鋼管樁工況下的可靠性;(4)驗(yàn)證本文提出的樁身受壓極限荷載計(jì)算方法。通過對試驗(yàn)數(shù)據(jù)進(jìn)行分析可以看出,(1)軸心受壓時(shí),靠近樁端處應(yīng)變最大,偏心受壓時(shí),靠近樁頂處應(yīng)變最大;荷載處于一定范圍內(nèi)時(shí),樁身應(yīng)變與支撐應(yīng)變呈線性關(guān)系,支撐應(yīng)變是樁身應(yīng)變的1/4~1/5倍,在破壞時(shí)倍值發(fā)生突變;(2)對于大比尺鋼管樁,試驗(yàn)所得穩(wěn)定性數(shù)值與課題組提出的虛擬嵌固點(diǎn)法較吻合,驗(yàn)證了虛擬嵌固點(diǎn)法的可靠性;(3)當(dāng)開挖比較小時(shí),屈曲破壞點(diǎn)出現(xiàn)在樁土接觸面附近,隨著開挖比的增大,破壞位置逐漸接近樁身中上部;(4)偏心受壓對樁身的承載力影響較大,偏心距為40mm以及80mm時(shí),極限荷載與軸心受壓對比,分別降低50%和65%;(5)施加水平支撐可以明顯提高樁身極限荷載,支撐設(shè)置在樁身中部時(shí)對極限荷載的提高作用更顯著;(6)開挖比較小時(shí),隨著回轉(zhuǎn)半徑的增大,鋼管樁的極限荷載增大;(7)對于軸心受壓樁和偏心受壓樁,提出了樁身極限荷載計(jì)算方法,通過與試驗(yàn)對比驗(yàn)證了本文提出的計(jì)算方法的可靠性。
[Abstract]:With the development of urbanization in our country, many existing buildings, because of the lack of underground parking facilities and other facilities, the defects in their use function are increasingly prominent, and the development and utilization of underground space of existing buildings has attracted more and more attention. When the existing building is added to the ground, it is necessary to first use the original pile foundation or set up a new pile foundation to bear the load of the existing building, then excavate the earth and add the basement. The stability of pile foundation will be reduced obviously during excavation of soil around pile. Steel tube pile foundation is one of the most commonly used pile foundations. It is of great significance to study the stability of steel tube pile by the method of large scale model test. In order to carry out the model test successfully, a 2.5m 脳 2.5m 脳 3.0m geotechnical model box was designed and manufactured. It consists of four sides of the vertical steel plate and the periphery through bolts connected to the horizontal hoop. After the angle steel on the four large angles of the model box and the adjacent vertical steel plate are fixed by bolts, the "temporary skeleton" of the model box can be formed, and the leakage of the soil filled in the box along the joint of the two plates can be prevented at the same time. The design method of vertical steel plate, horizontal hoop and connecting bolt of model box is put forward, and the design process of model box is introduced by an example. According to the condition that the soil is medium sand, the stability of the pile body under the condition of soil excavation around the pile with large scale steel pipe pile is studied experimentally in this paper. Through model experiments, (1) the load-strain variation of pile body and bracing under different excavation ratios is studied, (2) by changing the radius of rotation, eccentricity, support position, number of braces, stiffness of bracing, and so on, The ultimate buckling load of pile body is obtained by excavation ratio and other factors. The influence of different factors on pile stability is analyzed; (3) the reliability of virtual fixed point method proposed by the research group is verified under the condition of large scale steel pipe pile; (4) the method proposed in this paper is verified to calculate the ultimate load of pile under compression. Through the analysis of the test data, it can be seen that (1) the strain near the end of the pile is the largest when the axial center is under compression, and the strain near the top of the pile is the greatest when the load is in a certain range, the strain of the pile is linearly related to the strain of the support. The supporting strain is 1 / 4 / 1 / 5 times of the strain of pile body, and it has a sudden change during the failure. (2) for the large scale steel pipe pile, the stability obtained from the test is in good agreement with the fictitious fixed point method proposed by the research group. (3) when the excavation is small, the buckling failure point appears near the pile-soil contact surface, and with the increase of excavation ratio, the failure position is gradually close to the upper part of the pile body. (4) eccentric compression has a great effect on the bearing capacity of pile body. When the eccentricity is 40mm and 80mm, the ultimate load and axial compression are reduced by 50% and 65%, respectively. (6) the ultimate load of steel pipe pile increases with the increase of the radius of rotation when the support is set in the middle of the pile body. (7) for the axial compression pile and eccentric compression pile, the ultimate load of steel pipe pile increases with the increase of the radius of rotation. The calculation method of ultimate load of pile body is put forward, and the reliability of the proposed method is verified by comparing with the test.
【學(xué)位授予單位】：山東建筑大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU753.3

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