承臺技術方案.doc

（承臺施工工藝框圖附后）
1、基坑開挖
由于本合同段的承臺基坑開挖深度大多數在5.0m左右，最大深度在6.0m以內，地質情況以卵石為主，基坑開挖均采用無支護加固坑壁的形式。基坑采用挖掘機開挖，自卸車配合運輸，兩個基坑同時施工。基底平面尺寸按基礎平面尺寸四周各邊增寬150cm-200cm，以便在基礎底面外安置模板及設置排水溝和集水坑之用。基坑的形式采用斜坡式，坑壁坡度根據土類情況和基坑頂有無荷載確定，根據《公路橋涵施工技術規范》的規定，我部在基坑開挖時采用1：1和1：0.75的坡比對基坑分層進行開挖，首次開挖到地下水位處，約向下挖深2.5—3m，第一層邊坡按1：1的坡率設置，然后設置2m寬的工作平臺。開挖第二層時先降水再開挖，防止第二層邊坡下塌，開挖第二層邊坡按1：0.75的坡率設置，坑底邊距承臺邊留2m的工作平臺。基坑用草袋裝砂沿邊坡堆碼，以保持邊坡穩定。挖至設計標高時要保留不小于10～20cm的厚度，人工挖至基底高程，嚴禁超挖。用人工清理，鑿除樁頭進行檢測。基坑開挖前，首先要做好地面排水工作，在基坑頂緣四周向外設置排水坡，以免影響坑壁的穩定。開挖過程中和開挖以后，應注意觀察坑緣地面有無裂縫、坑壁有無松散塌落現象發生，否則應及時采取措施，按支護坑壁的形式施工。基坑挖成以后，若出現滲水、積水等情況，應將積水及時排入四周設置的集水坑，用6寸以上大口徑水泵水泵抽出。并施工中各工序必須安排緊湊，抓緊時間連續施工。
基底處理
基坑開挖完成以后，要根據基底不同土質，分別采取相應的處理方法。針對本合同段承臺的工程特點，基坑底部的地質情況屬于卵石層，坑底不允許暴露或浸水時間過長，并防止攪動。坑底找平夯實，采用10cm厚C15素混凝土墊層找平，作構造物底模之用，且其頂面應不高于基底高程。混凝土墊層邊緣要伸出承臺50cm。
2、立模、綁扎鋼筋
模板采用大塊鋼模，用鋼管連接支撐。立模前要做5cm的砂漿墊層，然后放樣。在基坑四角集中排水。
（1）支撐采用雙排鋼管支架，加木斜撐。支架搭設前處理好基礎，防止下沉。
（2）模板安裝
承臺（系梁）模板在安裝前，對模板表面進行清潔、校正、涂脫膜劑，安裝時用建筑雙面膠帶堵塞板縫，保證澆注砼時無漏漿。模板與支架緊密相連，一塊模板縱向至少與兩道架管相連。
模板及支撐加固牢靠后，對平面位置進行檢查，符合規范要求報監理工程師簽證后綁扎鋼筋。
同時在模板上部支架施工天橋，天橋支架
(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
 

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