本文關(guān)鍵詞： 靜載試驗(yàn) 數(shù)值分析 極限承載力預(yù)測 樁-土-樁相互作用 群樁效應(yīng)系數(shù) 地面超載荷載影響　出處：《廣西大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：為了準(zhǔn)確確定南寧市某高架平臺(tái)工程泥巖粉砂巖地基大直徑灌注樁的極限承載力,采用靜載試驗(yàn)對該工程兩根群樁基樁進(jìn)行靜載試驗(yàn)研究。然后,針對靜載試驗(yàn)中試樁未達(dá)到破壞時(shí)如何準(zhǔn)確估算大直徑灌注樁的極限承載力問題,采用函數(shù)擬合法來預(yù)測單樁的荷載沉降性狀和極限承載力,并對試樁試驗(yàn)進(jìn)行數(shù)值模擬反演分析,驗(yàn)證數(shù)值和計(jì)算參數(shù)的可靠性,并驗(yàn)證本文提出的指數(shù)函數(shù)擬合法預(yù)測該地基試樁荷載沉降性狀的適用性,再擴(kuò)展到群樁分析。同時(shí),針對大噸位堆載法樁基靜載試驗(yàn)中樁側(cè)支墩堆載荷載使試樁提前受荷所帶來的影響問題,本文結(jié)合實(shí)際工程試樁情況,通過對堆載法試樁試驗(yàn)進(jìn)行數(shù)值模擬分析,分析支墩荷載變化對試樁的影響。此外,針對該地基樁施工期間受樁側(cè)樁周地面大規(guī)模超高填土荷載作用下也會(huì)發(fā)生過大變形和樁身開裂問題,采用數(shù)值模擬分析法對自由單樁和既有受荷單樁分別受樁側(cè)和樁周大規(guī)模地面超載荷載影響展開研究。通過以上研究,可以得出以下結(jié)論：(1)對于該類地基中試樁未達(dá)到破壞時(shí)其極限承載力確定問題,可通過本文提出的指數(shù)函數(shù)擬合法和數(shù)值反分析法來預(yù)測其荷載沉降性狀和極限承載力；通過2×2無承臺(tái)群樁基樁和單樁的受荷性狀的數(shù)值模擬對比分析表明,受荷樁的非線性沉降會(huì)引起鄰近非受荷樁的彈性沉降,這種復(fù)雜的樁-土-樁相互作用降低了小間距群樁基樁的承載力。(2)在堆載法靜載試驗(yàn)過程中,在試驗(yàn)加載前樁側(cè)支墩荷載吊裝會(huì)使試樁提前受荷而發(fā)生沉降,但在試驗(yàn)中該部分沉降不被量測；在加載初期,受樁側(cè)堆載卸荷作用影響,堆載法對試樁剛度的夸大作用顯著；隨著加載至約為試樁極限荷載的一半(即Qu/2)后,其夸大作用開始明顯減弱,在接近極限荷載時(shí),其夸大作用不明顯,可忽略。從樁側(cè)堆載對試樁的影響來說,堆載法對試樁極限承載力的影響可忽略,大噸位堆載法仍是測試單樁極限承載力的可靠途徑。(3)在大規(guī)模地面荷載影響下,樁基受到的下拉荷載隨著地面荷載增加而增大,但存在峰值,達(dá)到峰值之后,下拉荷載反而下降；樁的附加沉降規(guī)律均近似隨地面荷載增加而呈線性增長；與樁側(cè)地面荷載作用下相比,樁周地面荷載影響下自由單樁和既有受荷樁的附加沉降均分別近似為前者的兩倍；與自由單樁相比,在相同的地面荷載作用下,既有受荷樁的附加沉降更大。在樁側(cè)地面荷載影響下,樁基發(fā)生側(cè)向變位和撓曲并受到橫向彎矩作用。本文研究成果可以為解決大噸位樁基靜載試驗(yàn)中試樁未達(dá)到破壞時(shí)其極限承載力的難以準(zhǔn)確確定問題提供參考,為評估堆載法樁基靜載試驗(yàn)中樁側(cè)堆載支墩荷載變化對試樁的影響和施工期間及工后樁基樁受地面堆載影響提供理論指導(dǎo)依據(jù),具有重要的理論價(jià)值和應(yīng)用價(jià)值。
[Abstract]:In order to accurately determine the ultimate bearing capacity of large diameter cast-in-place piles in mudstone siltstone foundation of an elevated platform project in Nanning City, static load test was used to study the static load of two pile groups. Aiming at the problem of how to estimate the ultimate bearing capacity of large diameter cast-in-place pile accurately when the pile failure is not reached in static load test, the function fitting method is used to predict the load settlement behavior and ultimate bearing capacity of single pile. The reliability of the numerical and computational parameters is verified, and the applicability of the exponential function fitting method proposed in this paper to predict the load-settlement behavior of the pile test foundation is verified, which is extended to the pile group analysis. In view of the influence of pile-side pier load on pile-side pile loading in static load test of pile foundation with large-tonnage surcharge method, combined with the actual engineering pile test situation, this paper carries out numerical simulation and analysis on pile test test by surcharge method. This paper analyzes the influence of load change of supporting pier on test pile. In addition, under the action of large scale and super high fill load on the ground around pile side pile during the construction of the foundation, the deformation and cracking of pile body will also occur. In this paper, numerical simulation analysis is used to study the influence of large scale ground overload on free single pile and existing loaded single pile on the side of pile and around pile respectively. The following conclusions can be drawn: (1) for the determination of ultimate bearing capacity of test pile in this kind of foundation when failure is not reached, the load settlement behavior and ultimate bearing capacity can be predicted by the exponential function fitting method and numerical inverse analysis method proposed in this paper. Through the numerical simulation and comparative analysis of 2 脳 2 uncapped pile group pile foundation and single pile, it is shown that the nonlinear settlement of the loaded pile will cause the elastic settlement of the adjacent unloaded pile. This complex pile-soil-pile interaction reduces the bearing capacity of small spaced pile groups. However, this part of the settlement is not measured in the test. In the early stage of loading, the overstatement effect of the surcharge method on the stiffness of the test pile is obvious under the influence of the unloading action of the pile side, and when the pile is loaded to about half of the ultimate load of the pile test (that is, Qu- / 2), The exaggeration effect begins to weaken obviously. When the load is near the limit load, the exaggeration effect is not obvious and can be ignored. From the influence of pile side load on pile test, the influence of surcharge method on ultimate bearing capacity of pile test can be neglected. Large-tonnage surcharge method is still a reliable way to test the ultimate bearing capacity of a single pile. Under the influence of large-scale ground load, the pull-down load of pile foundation increases with the increase of ground load, but there exists a peak value, after reaching the peak value. The additional settlement of pile increases linearly with the increase of ground load. Under the influence of the ground load around the pile, the additional settlement of the free single pile and the existing loaded pile are approximately twice as much as the former, and compared with the free single pile, under the same ground load, the additional settlement of the free single pile is similar to that of the existing pile under the same ground load. The additional settlement of the existing pile is greater. Under the influence of the ground load on the side of the pile, The lateral displacement and deflection of pile foundation are occurred and subjected to lateral bending moment. The research results in this paper can provide a reference for solving the problem of determining the ultimate bearing capacity of test pile when failure is not reached in the static load test of large-tonnage pile foundation. This paper provides a theoretical basis for evaluating the influence of pile load variation on test pile during construction and after construction in static load test of pile foundation by surcharge method, which has important theoretical value and application value.
【學(xué)位授予單位】：廣西大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU473.1

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本文編號(hào)：1526107