第三節(jié)：樁基工程一、混凝土預(yù)制樁施工-常見問題分析和處理49

1、第三節(jié)：樁基工程一、混凝土預(yù)制樁施工-常見問題分析和處理 執(zhí)教人：黃飛鷹一、復(fù)習(xí)1、樁基使用的原因防止天然地基上的淺土層沉降量過大或地基的承載力不能滿足設(shè)計(jì)要求，用下面的土層來承載。2、樁根底的組成樁身承臺 承臺梁樁的分類1、按承載性質(zhì)分摩擦型樁端承型樁2、按樁的制作工藝分預(yù)制樁現(xiàn)澆樁3、按材料分4、按成樁方法分等預(yù)制樁的施工方法1、打入法采用打樁機(jī)2、 壓入法采用壓樁機(jī)預(yù)制樁的構(gòu)造二、引入新課打入法施工過程中的討論 看著打樁機(jī)、聆聽著它的聲音，結(jié)合實(shí)際的例子，請大家思考一下樁打時以及打樁結(jié)束后常會碰到的問題，原因是什么？該如何處理？三、新課常見問題分析打壞打歪打不下 樁頂、樁身打壞的原因和處

2、理1、打樁時，樁的頂部由于直接受到?jīng)_擊而產(chǎn)生很高的局部應(yīng)力 -頂部的配筋應(yīng)做特別的處理。2、樁身的混凝土保護(hù)層太厚-主筋需擺正3、樁墊材料選用不適宜或打壞-采用材質(zhì)均勻、強(qiáng)度高、彈性好的樁墊4、樁的頂面與樁的軸線不垂直，局部受沖擊-保證垂直度，及時糾正5、過打現(xiàn)象。由于樁尖通過硬層等原因，使樁下沉速度慢而施打時間長，錘擊次數(shù)多或沖擊能量過大-分析土質(zhì)，改善操作方法6、樁身的混凝土強(qiáng)度不高，或未到達(dá)養(yǎng)護(hù)期，影響了樁的強(qiáng)度。-加鋼夾箍用螺栓拉緊焊牢打歪的原因和處理1、原因1樁頂不平、等樁的質(zhì)量問題，2與操作有關(guān)，如：初入土?xí)r，樁身就歪斜，未及時糾正就施打。2、處理方法1、保證打樁機(jī)的導(dǎo)架的垂直度2

3、、樁尖要對準(zhǔn)樁位，樁頂和樁帽要正確結(jié)合3、剛打時，要采用小落距，邊打邊檢查，穩(wěn)定后在按要求的落距打4、樁頂不平，產(chǎn)生樁尖偏心-保證樁的質(zhì)量打不下的原因和處理方法1、樁頂或樁身已打壞，無法有效地傳遞荷載 -拔出樁，與設(shè)計(jì)部門協(xié)商，再做處理。2、土層中夾有較厚的砂層或其它硬土層，或者遇上鋼渣、孤石等障礙物，仍進(jìn)行盲目施打。 -同設(shè)計(jì)勘探部門共同研究解決砂或硬土3、由于土的固結(jié)作用，使樁身周圍的土與樁牢固結(jié)合，鋼筋混凝土樁變成了直徑很大的土樁而承受荷載，很難繼續(xù)將樁打下去-應(yīng)在準(zhǔn)備條件完善的前提下，保證連續(xù)施打4、一樁打下，鄰樁上升。由于樁身土體受到擠密和擾動，容易造成近地面的地外表隆起和水平移動-

4、改變打樁的順序，由中間向兩邊對稱施打或中間向四周施打打入法的特點(diǎn)和有效措施1、特點(diǎn)土體擠壓造成土體隆起和位移，對周圍建筑物等存在危險，且噪音大2、措施開挖防震溝，搭隔離板樁等結(jié)合上述預(yù)制樁的打入法的特點(diǎn)，思考一下，還有其它的方法？1、靜力壓樁法。2、特點(diǎn)和適應(yīng)范圍作業(yè)布置1、預(yù)習(xí)靜力壓樁施工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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