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为弄清大直径超长桩端阻力承载特性,基于15个场地中共32根桩的现场试验资料,采用作图法、归一化处理法、数学模型拟合法研究了大直径超长桩端阻力随桩端沉降的发挥性状。发现,桩端阻力随桩端沉降的变化主要有3种类型,即类型一(近似直线增加型)、类型二(转折点后增幅大为变缓的双折线增加型)、类型三(转折点后增幅几乎为0的双折线增加型),3种类型代表着大直径超长桩的破坏型式大致分为类型三代表的桩端刺入破坏和类型一、类型二代表的桩端整体剪切或局部剪切破坏;玻耳兹曼数学模型拟合桩端阻力-桩端沉降归一化曲线的效果好,相关系数R2达0.95以上;桩端阻力达到极限状态时的桩端沉降值至少在0.444d―123.433d之间,显示超长桩端阻力极限状态时的桩端沉降基本上无定值,但大部分在1.00mm―40.00mm之间;注浆后的端阻力为注浆前的2.5倍以上。结果表明,超长桩的端阻力不能被忽略,应加强研究,应充分利用它。
In order to find out the bearing characteristics of large-diameter over-long pile tip resistance, based on the field test data of 32 piles in 15 sites, the resistance of large-diameter overlength pile end was studied by using the method of drawing, normalization and mathematical model fitting With the settlement of the pile to play the character. It is found that there are three main types of changes in the pile tip resistance with the settlement of the pile head: type one (approximate linear increase type), type two (increase rate of diurnal increase after the turning point is much slower), type three Almost double the number of double-line increase), three types of large-diameter super-long pile representative of the failure type is divided into three types of representatives of the pile end piercing damage and type a, type two on behalf of the overall pile tip cut or partial Shear failure; Boltzmann mathematical model to fit the pile end resistance - pile end settlement normalization curve is good, the correlation coefficient R2 reaches above 0.95; pile end resistance reaches the limit state pile tip settlement at least 0.444d -123.433d, it shows that the pile tip settlement at the extreme pile end resistance limit state is basically indefinite, but most of them are between 1.00mm-40.00mm; the end resistance after grouting is 2.5 times before grouting the above. The results show that the end resistance of the super-long pile can not be neglected, and should be strengthened to make full use of it.