本文選題：大直徑擴底灌注樁 + 球孔擴張理論��； 參考：《山東科技大學(xué)》2017年碩士論文

【摘要】：大直徑擴底灌注樁具有承載力高、沉降小、穩(wěn)定性好等優(yōu)點,被廣泛應(yīng)用于大跨度橋梁、高聳結(jié)構(gòu)中。迄今為止,大直徑擴底灌注已在我國發(fā)展三十多年,在機械成孔和沉降計算方面均取得長足的進步,對于橫向荷載作用下的動靜力響應(yīng)特性研究也在蓬勃發(fā)展;但由于擴大端的存在,其設(shè)計中機械成孔的擴孔壓力大小,豎向荷載作用下的沉降計算及地震荷載作用下的抗震特性與等直徑樁相比,存在較大差異。因此,本文對大直徑擴底樁的球孔擴孔壓力計算、豎向荷載作用下的沉降計算以及地震荷載作用下的動力響應(yīng)分析等方面進行研究,以期完善大直徑擴底灌注樁的設(shè)計計算理論。主要內(nèi)容包括:(1)擴底樁擴孔壓力的理論研究�；诳臻g準(zhǔn)滑動面(SMP)準(zhǔn)則,考慮塑性區(qū)彈性變形,從能量耗散的角度分析球孔擴張的全過程,利用應(yīng)力不變量推導(dǎo)符合球孔擴張的屈服準(zhǔn)則,分別導(dǎo)出彈塑性區(qū)應(yīng)力、位移、應(yīng)變表達式;利用體積守恒和能量守恒推導(dǎo)出擴孔壓力的表達式,并給出擴孔壓力P、塑性區(qū)半徑R與擴孔半徑a的關(guān)系。算例分析可知,本文方法計算的擴孔壓力與現(xiàn)場試驗得出的結(jié)果較好的吻合,塑性區(qū)半徑和擴孔壓力均隨擴孔半徑的增加而增大,但增幅逐漸減小而趨于穩(wěn)定值,剪脹角對塑性區(qū)半徑和擴孔壓力影響顯著,隨著剪脹角的增加,塑性區(qū)半徑和擴孔壓力明顯增加。(2)擴底樁的沉降計算方法�？紤]壓縮模量的深度效應(yīng),對已有的大直徑擴底灌注樁沉降計算公式進行修正。取土體微單元進行受力分析,并引入深度對壓縮模量的影響,建立室內(nèi)壓縮模量與變形模量的關(guān)系,代入擴底樁沉降計算公式,得出擴底樁沉降計算修正公式。分別采用修正前和修正后的計算公式對某工程實例進行沉降計算。結(jié)果表明,修正后的計算結(jié)果與實測數(shù)據(jù)吻合更好。同時,數(shù)值計算結(jié)果也表明,與壓縮模量Es修正前的計算沉降相比,壓縮模量Es修正后的計算沉降與實測沉降更加吻合。(3)擴底樁在地震荷載作用下的動力響應(yīng)分析。樁周土采用Drucker-Prager彈塑性模型,以考慮土體的非線性;樁與樁周土之間設(shè)置接觸以考慮樁—土接觸非線性;通過借助ABAQUS有限元軟件,分別建立地震荷載作用下擴底樁—土—結(jié)構(gòu)和普通樁—土—結(jié)構(gòu)相互作用體系的三維有限元動力模型。對兩種樁基進行時域內(nèi)的數(shù)值模擬研究,分析兩種不同樁基的抗震性能差異,并探討樁土模量比、阻尼比、軟夾層、上部質(zhì)量等因素對樁基相互作用問題的影響。
[Abstract]:Large diameter reamed cast-in-place piles with high bearing capacity, small settlement and good stability are widely used in long-span bridges and high-rise structures.Up to now, large diameter bottom filling has been developed in China for more than 30 years, and great progress has been made in the field of mechanical hole formation and settlement calculation, and the research on the dynamic and dynamic response characteristics under transverse loads is also booming.However, due to the existence of the enlarged end, there is a great difference between the pressure of the mechanical hole reaming, the settlement calculation under vertical load and the seismic characteristics under the earthquake load compared with the equal diameter pile.Therefore, in this paper, the calculation of pressure of bulbous hole, settlement calculation under vertical load and dynamic response analysis under earthquake load of large diameter belled pile are studied.The purpose of this paper is to perfect the design and calculation theory of large diameter reamed cast-in-place pile.The main contents include the theoretical study of reaming pressure of reamed pile.Based on the spatial quasi-sliding surface (SMP) criterion, considering elastic deformation in plastic zone, the whole process of spherical hole expansion is analyzed from the angle of energy dissipation. The yield criterion consistent with spherical hole expansion is derived by using stress invariant, and the stress and displacement in elastic-plastic zone are derived respectively.The expression of strain is derived by using volume conservation and energy conservation, and the relation between reaming pressure P, plastic radius R and reaming radius a is given.The analysis of example shows that the pressure calculated by this method is in good agreement with the result of field test. The radius of plastic zone and the pressure of reaming increase with the increase of the radius of reaming, but the increase decreases gradually and tends to be stable.The influence of expansion angle on the radius of plastic zone and the pressure of reaming hole is significant. With the increase of expansion angle, the radius of plastic zone and the pressure of reaming hole increase obviously.Considering the depth effect of compression modulus, the existing formulas for calculating settlement of large-diameter belled cast-in-place piles are modified.The relationship between compression modulus and deformation modulus is established by introducing the influence of depth on compression modulus, and the calculation formula of pile settlement is put in place, and the modified formula is obtained.The calculation formulas before and after modification are used to calculate the settlement of an engineering example.The results show that the calculated results are in better agreement with the measured data.At the same time, the numerical results also show that compared with the calculated settlement before the compression modulus es correction, the calculated settlement after the compression modulus es correction is more consistent with the measured settlement.The Drucker-Prager elastoplastic model is adopted to consider the nonlinearity of soil mass, the contact between pile and soil around pile is set to consider the nonlinearity of pile-soil contact, and the nonlinear contact between pile and soil is considered by means of ABAQUS finite element software.Three dimensional finite element dynamic models of pile-soil-structure and pile-soil-structure interaction systems under seismic loads are established respectively.In this paper, numerical simulation of two kinds of pile foundations in time domain is carried out. The difference of seismic behavior of two kinds of pile foundations is analyzed, and the effects of pile-soil modulus ratio, damping ratio, soft interlayer and upper mass on pile-foundation interaction are discussed.
【學(xué)位授予單位】：山東科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TD350

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