承台技术方案.doc

（承台施工工艺框图附后）
1、基坑开挖
由于本合同段的承台基坑开挖深度大多数在5.0m左右，最大深度在6.0m以内，地质情况以卵石为主，基坑开挖均采用无支护加固坑壁的形式。基坑采用挖掘机开挖，自卸车配合运输，两个基坑同时施工。基底平面尺寸按基础平面尺寸四周各边增宽150cm-200cm，以便在基础底面外安置模板及设置排水沟和集水坑之用。基坑的形式采用斜坡式，坑壁坡度根据土类情况和基坑顶有无荷载确定，根据《公路桥涵施工技术规范》的规定，我部在基坑开挖时采用1：1和1：0.75的坡比对基坑分层进行开挖，首次开挖到地下水位处，约向下挖深2.5—3m，第一层边坡按1：1的坡率设置，然后设置2m宽的工作平台。开挖第二层时先降水再开挖，防止第二层边坡下塌，开挖第二层边坡按1：0.75的坡率设置，坑底边距承台边留2m的工作平台。基坑用草袋装砂沿边坡堆码，以保持边坡稳定。挖至设计标高时要保留不小于10～20cm的厚度，人工挖至基底高程，严禁超挖。用人工清理，凿除桩头进行检测。基坑开挖前，首先要做好地面排水工作，在基坑顶缘四周向外设置排水坡，以免影响坑壁的稳定。开挖过程中和开挖以后，应注意观察坑缘地面有无裂缝、坑壁有无松散塌落现象发生，否则应及时采取措施，按支护坑壁的形式施工。基坑挖成以后，若出现渗水、积水等情况，应将积水及时排入四周设置的集水坑，用6寸以上大口径水泵水泵抽出。并施工中各工序必须安排紧凑，抓紧时间连续施工。
基底处理
基坑开挖完成以后，要根据基底不同土质，分别采取相应的处理方法。针对本合同段承台的工程特点，基坑底部的地质情况属于卵石层，坑底不允许暴露或浸水时间过长，并防止搅动。坑底找平夯实，采用10cm厚C15素混凝土垫层找平，作构造物底模之用，且其顶面应不高于基底高程。混凝土垫层边缘要伸出承台50cm。
2、立模、绑扎钢筋
模板采用大块钢模，用钢管连接支撑。立模前要做5cm的砂浆垫层，然后放样。在基坑四角集中排水。
（1）支撑采用双排钢管支架，加木斜撑。支架搭设前处理好基础，防止下沉。
（2）模板安装
承台（系梁）模板在安装前，对模板表面进行清洁、校正、涂脱膜剂，安装时用建筑双面胶带堵塞板缝，保证浇注砼时无漏浆。模板与支架紧密相连，一块模板纵向至少与两道架管相连。
模板及支撑加固牢靠后，对平面位置进行检查，符合规范要求报监理工程师签证后绑扎钢筋。
同时在模板上部支架施工天桥，天桥支架
(Slab construction process diagram attached)
1 excavation
Since the contract section of the cap excavation depth about most of the 5.0m maximum depth of 6.0m within the geological conditions in gravel-based, are used without excavation support in the form of reinforcement Pit. Excavation pit with excavators, dump trucks with transport, two pit simultaneously. Basal plane size based on planar dimension by broadening the sides around 150cm-200cm, so that placement in the basic template and set the outside bottom drains and sump use. The form of pit with sloping, Pit slope foundation based on soil conditions and top class load to determine whether, under the "highway bridge construction specifications" requirement, the Department of excavation I used 1:1 and 1: The slope ratio of 0.75 for excavation of the foundation layer, the first excavation to the groundwater level office, down the deepening of about 2.5-3m, the first layer of slope by slope ratio of 1:1 set, then set 2m wide working platform. Excavation of the second layer re-excavation of the first precipitation, the second layer to prevent slope collapse, excavation second slope by slope ratio 1:0.75 set, bottom left side of cap margin 2m working platform. Foundation along with the grass slope stacking sand bags to maintain slope stability. Dredged to the design elevation to retain no less than when the thickness of 10 ~ 20cm, dug to the base of artificial elevation, is strictly prohibited overbreak. Manually clean up the hammer except pile head for testing. Excavation, we should first do the work surface drainage in the foundation around the top edge of the field and provision of drainage slope, so as not to affect the stability of the Pit. During and after excavation excavation should observe whether the pit edge surface crack, with or without loose Pit collapse phenomenon, or should take timely measures, according to the form of support Pit Construction. Pit dug into the future, if the water seepage, water, etc., should be discharged into the surrounding water in time to set the sump, with more than 6-inch pump out large-caliber pump. And to arrange for the construction of the compact process, seize the time continuous construction.
Bed Treatment
Excavation is completed, according to different soil substrates, respectively, the appropriate approach to take. Cap segment of the contract for the engineering characteristics of the geological conditions are bottom of the pit gravel layer, bottom does not allow exposure to or soaking for too long, and to prevent agitation. Bottom leveling compaction, use of plain concrete 10cm thick C15 leveling cushion for the bottom model structures used, and its top should be no higher than the base elevation. To extend the edge of concrete pile cap cushion 50cm.
2, formwork, steel banding
Template by large steel, with steel connection support. Formwork done before the mortar 5cm cushion, and then lofting. Concentration of water in the pit corners.
(1) support the use of double steel frame, with timber bracing. Dealt with before the foundation Scaffording to prevent sinking.
(2) template installation
Cap (tie beam) before installing the template, the template surface cleaning, calibration, Tu releasing agent, install double-sided tape used building block seams, to ensure seamless when the casting of concrete slurry. Closely connected with the bracket template, a template with at least two longitudinal frame tube connected.
Strong reinforcement templates and support after the inspection of the plane position, with the required supervision engineers reported visa steel banding.
While the upper bracket in the template construction of flyovers, bridges bracket