第三节：桩基工程一、混凝土预制桩施工-常见问题分析和处理49

1、第三节：桩基工程一、混凝土预制桩施工-常见问题分析和处理 执教人：黄飞鹰一、复习1、桩基使用的原因防止天然地基上的浅土层沉降量过大或地基的承载力不能满足设计要求，用下面的土层来承载。2、桩根底的组成桩身承台 承台梁桩的分类1、按承载性质分摩擦型桩端承型桩2、按桩的制作工艺分预制桩现浇桩3、按材料分4、按成桩方法分等预制桩的施工方法1、打入法采用打桩机2、 压入法采用压桩机预制桩的构造二、引入新课打入法施工过程中的讨论 看着打桩机、聆听着它的声音，结合实际的例子，请大家思考一下桩打时以及打桩结束后常会碰到的问题，原因是什么？该如何处理？三、新课常见问题分析打坏打歪打不下 桩顶、桩身打坏的原因和处

2、理1、打桩时，桩的顶部由于直接受到冲击而产生很高的局部应力 -顶部的配筋应做特别的处理。2、桩身的混凝土保护层太厚-主筋需摆正3、桩垫材料选用不适宜或打坏-采用材质均匀、强度高、弹性好的桩垫4、桩的顶面与桩的轴线不垂直，局部受冲击-保证垂直度，及时纠正5、过打现象。由于桩尖通过硬层等原因，使桩下沉速度慢而施打时间长，锤击次数多或冲击能量过大-分析土质，改善操作方法6、桩身的混凝土强度不高，或未到达养护期，影响了桩的强度。-加钢夹箍用螺栓拉紧焊牢打歪的原因和处理1、原因1桩顶不平、等桩的质量问题，2与操作有关，如：初入土时，桩身就歪斜，未及时纠正就施打。2、处理方法1、保证打桩机的导架的垂直度2

3、、桩尖要对准桩位，桩顶和桩帽要正确结合3、刚打时，要采用小落距，边打边检查，稳定后在按要求的落距打4、桩顶不平，产生桩尖偏心-保证桩的质量打不下的原因和处理方法1、桩顶或桩身已打坏，无法有效地传递荷载 -拔出桩，与设计部门协商，再做处理。2、土层中夹有较厚的砂层或其它硬土层，或者遇上钢渣、孤石等障碍物，仍进行盲目施打。 -同设计勘探部门共同研究解决砂或硬土3、由于土的固结作用，使桩身周围的土与桩牢固结合，钢筋混凝土桩变成了直径很大的土桩而承受荷载，很难继续将桩打下去-应在准备条件完善的前提下，保证连续施打4、一桩打下，邻桩上升。由于桩身土体受到挤密和扰动，容易造成近地面的地外表隆起和水平移动-

4、改变打桩的顺序，由中间向两边对称施打或中间向四周施打打入法的特点和有效措施1、特点土体挤压造成土体隆起和位移，对周围建筑物等存在危险，且噪音大2、措施开挖防震沟，搭隔离板桩等结合上述预制桩的打入法的特点，思考一下，还有其它的方法？1、静力压桩法。2、特点和适应范围作业布置1、预习静力压桩施工2、P89 / 13、15y+B2E6H9LcOfRjUmXp!s&w)z0C4F7IaMdPhSkVnZq$t*x-A1D5G8KbNeQiTlWo#r%v(y+B3E6H9LcOgRjUmYp!s&w)z1C4F7JaMdPhSkWnZq$u*x-A2D5H8KbNfQiTlXo#s%v(y0B3E6I

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