灌注嵌岩桩承载力性状及嵌岩深度研究

【作者】 张有祥；

【导师】 李彰明；

【作者基本信息】 广东工业大学 ， 岩土工程， 2005， 硕士

【摘要】 本文对嵌岩桩的研究现状进行了综述及讨论,在此基础上对嵌岩桩的特性及合理嵌岩深度开展研究,通过原位测试获得嵌岩桩力学响应的第一手资料,并对其工作机理及力学响应规律进行分析、讨论与计算,主要工作: 一、在试验方面,以潮州电厂、惠州电厂和汕尾电厂尾工程背景,现场进行了桩基静载试验,主要包括桩基的沉降测试和桩身的应力应变测试,并结合理论分析得到以下结论: 1、桩长和桩的长径比均小于25的嵌岩桩,其端阻力与桩顶荷载比一般大于50%;桩长和桩的长径比均大于25小于40的嵌岩桩,桩端阻力与桩顶荷载比一般在30～40%,桩长和桩的长径比均大于40的嵌岩桩,其桩端阻力与桩顶荷载比一般小于30%。 2、嵌岩桩的P-S曲线有两种:a、对于桩长和桩的长径比均小于40的嵌岩桩,其P-S曲线可近似的认为是一直线,该直线斜率由桩端岩层强度控制;b、桩长和桩的长径比均大于40的嵌岩桩,其P-S一般分为两个线性段,第一个线性部分由桩底沉渣的厚度和强度控制,第二个线性段由桩端岩层强度控制。 3、对于桩长和桩的长径比均小于25的嵌岩桩,侧阻力随桩顶荷载的增加而增大,且在高的应力水平下平缓增长,当达到最大荷载时达到试验最大值,其嵌岩部分侧阻力从上至下依次发挥。对桩长和桩的长径比均大于25小于40的嵌岩桩,其上部土层侧阻力均有较好的发挥,但其试验最大值主要集中在后几级荷载作用下;嵌岩部分的侧阻力发挥情况与桩长和桩的长径比均小于25的嵌岩桩一样。对于桩长和桩的长径比均大于40的嵌岩桩,其上部土层侧阻力有可能在较小的桩顶荷载作用下就会达到试验最大值,其嵌岩段的侧阻力发挥程度从上至下依次渐弱。 二、在理论分析及计算方面,本文对土体采用Mohr-Coulomb准则,对岩体采用Hock-Brown准则,通过Flac3D软件计算分析,同时结合施工条件和经济合理的原则,得到以下有益的结果: 1、在清底干净的条件下,嵌岩桩的桩顶沉降与桩长有良好的线性关系。 2、对于直径为1.0米的嵌岩桩,其桩顶沉降随桩直径增加而增大,因此在满足承载力前提下,选择较小的桩直径。 3、在土层厚度19米左右,嵌岩深度1.0米,同时满足桩身强度的条件下,桩身混更多还原

【Abstract】 Study situation of rock-socketed pile is summarized and discussed in this thesis, on the base of this characters of rock-socketed pile and reasonable rock-socketed length are studied. The first datum about mechanical response of rock-socketed pile are abstained, task mechanism and mechanical response rule are discussed and calculated. Main work: 一、 static test of pile is done containing settlement measure and stain-stress test on the basis of chaozhou, huizhou and shanwei electrical plant. The conclusions is abstained combining the theory analysis as follow:1、 When pile length and the ratio about pile length to pile diameter is less than 25, the ratio about the tip resistance to the top pile load is more than 50 per generally; When pile length and the ratio about pile length to pile diameter is less than 40 and more than 25, the ratio about the tip resistance to the top pile load is between 40 and 50 per generally; When pile length and the ratio about pile length to pile diameter is more than 25, the ratio about the tip resistance to the top pile load is less than 50 per generally.2、 There is two P-S curve of rock-socketed pile: a、 When pile length and the ratio about pile length to pile diameter is less than 40, the P-S curve is a line approximately, he line slope is controlled by the rock strength; b、 When pile length and the ratio about pile length to pile diameter is more than 40, the P-S curve is divided to two lines, the first line is controlled by the subsidence thickness and strength, and the second line by the rock strength.3、 When pile length and the ratio about pile length to pile diameter is less than 25, side resistance is aggrandized by increasing of the load, and gently added at high stress level. The test maximum is reached at the max load, and rock-rocketed side resistance is exerted in turn from top to tip. When pile length and the ratio about pile length to pile diameter is more than 25 and less than 40, side resistances of top soil layers are exerted preferably, but the test maximum is reached at the late several loads. rock-rocketed side resistance is exerted in turn from top to tip. When pile length and the ratio about pile length to pile diameter is more than 40, side resistances of top soil更多还原