浅析水下封底混凝土钢套箱施工技术
浅析水下封底混凝土钢套箱施工技术
[摘要]:有底套箱围堰适用于承台底面距河床面较高(高桩承台) 、且河流水面标高高于承台混凝土底面标高的情况,浇筑水下封底混凝土的目的是为了实现承台的干施工:将内装有扁担梁的钢吊箱围堰悬挂在固定于钻孔桩内的支柱顶或钢护筒顶,然后利用千斤顶或滑轮组将围堰整体下沉入水,到达指定位置后固定套箱、灌注水下混凝土封底,抽水后浇筑承台混凝土,此工艺施工方便,防水性好,因围堰不进入河床而是悬吊于水中,所用钢量少、下沉时间短,质量容易控制,节省模板,易拆除再利用。
[关键词]: 水下封底混凝土套箱 施工技术
Abstract: Bottom boxed cofferdam apply to the pile cap underside away from the riverbed surface high (high pile cap), and the river water surface elevation above the elevation of the pile cap concrete underside pouring underwater sealing concrete purpose is to dry pile cap construction: built-in pole beam steel cofferdam was hanging in the pillar top bored piles or steel casing, top, and then use the jack or the pulley will cofferdam sink into the water as a whole to reach the designated fixed set of boxes in the position, pouring underwater concrete back cover, pumping after pouring pile cap concrete, to facilitate this process of construction, waterproof cofferdam does not enter the river bed but suspended in the water, the steel is less time sinking, quality, easy to control, save the template, easy to dismantle and reuse.Key words: underwater back cover concrete; sets of boxes; construction technology
1、工程简介
郧县汉江二桥的主桥与引桥的44号交界墩位于汉江主河道内,承台设计为哑铃形,平面尺寸如下图所示,承台厚度设计3.5m ,承台混凝土方量584m3;水下封底混凝土设计2m 厚的c20混凝土,封底混凝土方量334m3,承台底面标高150.000m 、封底混凝土底面标高148.000m 。承台底面距河床面12.4m 。枯水季节水位标高143-145m ,蓄水期水面标高153m 以内,即最大施工水深按5m 考虑,因工期紧迫、施工时正处于蓄水期内。
2、施工方案简述
封底混凝土施工采用单壁有底钢套箱进行水下施工。钢套箱采用现场加工的模板和加劲肋等组合而成,钢套箱尺寸与承台尺寸相对应,侧板兼作承台模板,高6m (封底厚2m +3.5m 承台厚+0.5m水平支撑预留空间)。
钢套箱在钻孔平台上组拼成整体,然后两侧承台(相当于哑铃两端)利用预埋在每个钻孔桩内的2根56b 工字钢(利用缀板焊接成整体的墩式结构,工字钢