本文關(guān)鍵詞： 變截面樁 荷載傳遞機理 靜載荷試驗 室內(nèi)模型試驗 擴大頭　出處：《東華理工大學》2017年碩士論文　論文類型：學位論文

【摘要】：全夯式多頭混凝土擴灌樁具有擠密樁周圍土體、增大樁身和樁端作用面積的作用。它在各類型的建筑工程中改進了傳統(tǒng)的地基基礎的處理方式,它具有承載力高、穩(wěn)定性強的優(yōu)點,可以改善不均勻沉降,具有良好的性能。然而在其工程應用過程中在承載機理、承載力計算方法、夯擴擠密效果等方面仍然存在一些問題,針對單樁豎向承載機理問題本文將展開深入的研究。首先,通過室內(nèi)模型試驗,針對全夯式多頭混凝土擴灌樁的荷載沉降曲線、樁周土體的擠密影響范圍和不同擴大頭間距進行了研究,在均質(zhì)砂土、均質(zhì)黏土場地條件下與夯擴樁和普通直樁相比較,根據(jù)土壓力計的測試結(jié)果顯示,土體壓力在樁端擴大頭正下方是荷載最大,其次就是斜下方的位置,最后就是擴大頭的縱方向處,擴大頭之間的距離應大于2倍擴大頭直徑為宜;在施加荷載階段,荷載沉降曲線前期變化比較平緩,繼續(xù)荷載的增加荷載沉降曲線表現(xiàn)為“雙峰”,顯示出了樁身擴大頭和樁端擴大頭分散荷載,增大單樁豎向承載力的影響。其次,本文利用有限差分分析軟件對全夯式多頭混凝土擴灌樁擴大頭之間的距離對荷載傳遞的影響、樁周圍土體的應力應變和樁身軸力變化進行了分析。通過與普通直樁和夯擴樁之間的分析結(jié)果可知,其極限單樁承載力約為普通直樁的1.5~2.5倍,夯擴樁的1~1.5倍;砂土中擴大頭周圍土體的應力向下和向兩側(cè)擴散均比較明顯,土體的應力在擴大頭上下位置變化很大,擴大頭下方土體承擔了較多的荷載;在對樁頂加載過程中,擴大頭頂部出現(xiàn)擴張帶;地基土為均質(zhì)土體時該樁型破壞模式為刺入破壞。再次,將現(xiàn)場試驗數(shù)據(jù)與理論及模型試驗作對比,該數(shù)據(jù)和理論計算分析的結(jié)果相符合,揭示出了荷載的傳遞特性,同時也進一步驗證了承載力計算方法的合理性。最后,本文對全夯式多頭混凝土擴灌樁的荷載傳遞的規(guī)律進行了理論分析,其主要通過全夯式多頭混凝土擴灌樁豎向受壓承載機理、破壞模式、樁身擴大頭阻力影響分析以及樁端擴大頭阻力影響分析等方面進行分析,得出了其單樁豎向承載的相關(guān)因素和特點并將承載傳遞機理與工程實踐相結(jié)合,考慮多重因素推導出相對合適的全夯式多頭混凝土擴灌樁單樁豎向承載力計算公式。
[Abstract]:Full compaction concrete expansion grouting pile has the function of soil around compaction pile and increasing the action area of pile body and pile tip. It improves the traditional treatment method of foundation foundation in all kinds of construction projects, and it has high bearing capacity. The advantages of strong stability can improve uneven settlement and have good performance. However, there are still some problems in carrying mechanism, calculation method of bearing capacity, compaction and compaction effect in engineering application. In this paper, the vertical bearing mechanism of single pile will be studied deeply. Firstly, through indoor model test, the load settlement curve of full rammed multi-head concrete pile is studied. The influence range of compaction of soil around pile and the distance between different enlarged heads are studied. Compared with rammed pile and ordinary straight pile in homogeneous sand and homogeneous clay soil, the test results of soil pressure gauge show that, The pressure of the soil is the largest at the end of the pile, followed by the position below the slope. Finally, the longitudinal direction of the head is enlarged. The distance between the enlarged heads should be more than 2 times the diameter of the head; at the stage of loading, the distance between the enlarged heads should be more than 2 times the diameter of the head. The initial variation of load settlement curve is relatively gentle, and the increasing load settlement curve of continuous load is shown as "double peak", which shows the influence of spreading load on the enlarged head of pile body and on the expanded head of pile end, which increases the vertical bearing capacity of single pile. In this paper, the finite difference analysis software is used to analyze the influence of the distance between the expansion and grouting piles of full rammed multi-head concrete on the load transfer. The stress and strain of the soil around the pile and the axial force of the pile body are analyzed. The results of the analysis with the ordinary straight pile and rammed pile show that the ultimate bearing capacity of the single pile is about 1.52.5 times of that of the ordinary pile, and that of the rammed pile is 1 / 1.5 times of that of the rammed pile. The stress of the soil around the expanded head in sand is obviously diffused down and to both sides. The stress of the soil changes greatly in the upper and lower position of the expanded head, and the soil under the expanded head bears more loads; in the process of loading the pile top, The expansion zone appears at the top of the enlarged head, and the pile failure mode is pierced when the foundation soil is homogeneous soil. Thirdly, the field test data are compared with the theoretical and model tests, and the results of the theoretical calculation and analysis are consistent. The characteristics of load transfer are revealed, and the rationality of the calculation method of bearing capacity is further verified. Finally, the law of load transfer of fully rammed multi-head concrete pile is theoretically analyzed in this paper. It is mainly analyzed from the aspects of the mechanism of vertical compression bearing, failure mode, the influence analysis of the resistance of the enlarged head of pile body and the influence analysis of the resistance of the expanded head of pile end, etc. The related factors and characteristics of vertical bearing capacity of single pile are obtained, and the bearing transfer mechanism is combined with engineering practice. Considering multiple factors, a relatively suitable formula for calculating vertical bearing capacity of single pile with full tamping concrete expansion pile is derived.
【學位授予單位】：東華理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU473.1

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