【正文】 n Construction preparation prise: selecting drill, drill, layout. Construction of bored pile drilling rig is the main equipment, according to the geological conditions and various drilling machine applied to select conditions (2) drilling machine installation and positioning Istallation of drilling machine based if not stable, easy to produce in the drilling machine construction, pile and pile inclined inclined eccentric and other adverse effects, therefore requires the installation of foundation stability. On the formation of softer, sloping ground, be bulldozed, the pad plate or tie reinforcement. In order to prevent the pile position allowed, construction is very important to the set the center position and the correct installation of drilling machine, the rig drilling machine, first use of the power drill and near the cage with the drill pipe, moving roughly position, and then Jack rack jacking, accurate positioning, so that the lifting pulley, drill bit or fixed drill hole cards and casing center in a vertical line, in order to ensure the verticality of the drilling rig. Drilling position deviation is not more than 2cm. Aligned with the pile location, with sleeper flat drill beam at the top of the tower, and symmetrical to the drill axis pulling cable wind rope. (3) buried tube Underground water level below the Kong Bitu under the hydrostatic pressure to the hole collapse, and even the phenomenon of flow of sand. If you can keep the borehole wall high underground water head, increase the hole hydrostatic pressure, to prevent collapse hole, hole wall. Casing in addition to play this role, at the same time, good isolation of surface water, ground, protecting the orifice pile hole drill guide fixed (4) slurry preparation Drilling mud is posed of water, clay ( bentonite ) and an additive position. A floating drilling waste slag cooling the drill bit, drill, lubrication, increasing hydrostatic pressure, and in the hole wall to form a slurry, partition within the bore to prevent seepage, the hole collapse effect. Modulation of the drilling mud and circulating purifying mud, should be based on the drilling method and formation conditions to determine the slurry consistency, slurry consistency should be considered stratigraphic changes or operational requirements of motor control, the mud is too thin, small, poor effect of elimination of slag wall。大直徑灌注樁因此得到快速發(fā)展，樁長(zhǎng)和樁徑也越做越大。該施工法的過程是：平整場(chǎng)地 → 泥漿制備 → 埋設(shè)護(hù)筒 → 鋪設(shè)工作平臺(tái) → 安裝鉆機(jī)并定位 →鉆進(jìn)成孔 → 清孔并檢查成孔質(zhì)量 → 下放鋼筋籠 → 灌注水下混凝土 → 拔出護(hù)筒 →檢查質(zhì)量。 （ 3）埋設(shè)護(hù)筒 鉆孔成敗的關(guān)鍵是防止 孔壁 坍塌。在施工中要注意不斷添加泥漿和抽渣 (沖擊式用 )，還要隨時(shí)檢查成孔是否有偏斜現(xiàn)象。對(duì)于柱樁，要求在射水或射風(fēng)前，沉渣厚度不大于 5cm。所有這些都影響了鉆孔灌注樁承載力的發(fā)揮。這正是鉆孔灌注樁承載效益不高的另一原因。先灌漿法 是在鉆孔樁成孔后至灌注混凝土前進(jìn)行灌漿，即將噴頭鐵管放入孔底插入虛土，噴射水泥漿，使樁底虛土與水泥混合，最后再灌注樁身混凝土。樁身內(nèi)力和位移都比同樣水平外力作用下低樁承臺(tái)要大，其穩(wěn)定性因?yàn)楸鹊蜆冻信_(tái)差。 。高樁承臺(tái)由于具有一段自由長(zhǎng)度，其周圍無支撐體共同承受水平外力。 (3)砂襯樁技術(shù)：該法用于沉管灌注樁，施工時(shí)，利用雙層套管在樁周圍灌砂，成為砂套約 3～ 10cm，砂套的存在可提高樁側(cè)壁的摩阻力。 研究表明，樁底虛土的存在，不僅影響端阻的發(fā)揮，也使側(cè)摩阻力受到損失。 影響鉆孔灌注樁承載性能的因素 在施工過程中，由于地質(zhì)、施工機(jī)械的影響，常造成樁底虛土（軟弱層段），其厚度一般為 ～ ，厚者可達(dá) 1m。在終孔檢查完全符合設(shè)計(jì)要求時(shí)，應(yīng)立即進(jìn)行孔底清理，避免隔時(shí)過長(zhǎng)以致泥漿沉淀，引起鉆孔坍塌。調(diào)制的鉆孔泥漿及經(jīng)過循環(huán)凈化的泥漿，應(yīng)根據(jù)鉆孔方法和地層情況來確定泥漿稠度，泥漿稠度應(yīng)視地層變化或操作要求機(jī)動(dòng)掌握，泥漿太稀，排渣能力小、護(hù)壁效果差；泥漿太稠會(huì)削弱鉆頭沖擊功能，降低鉆進(jìn)速度。鉆機(jī)位置的偏差不大于 2cm。 鉆孔灌注樁的特點(diǎn) 與沉入樁中的錘擊法相比，施工噪聲和震動(dòng)要小的多； 能建造比預(yù)制樁的直徑大的多的樁； 在各種地基上均可使用； 施工質(zhì)量的好壞對(duì)樁的承載力影響很大； 因混凝土是在泥水中灌注的，因此混凝