介绍了某熔铸车间设备基础铸造机沉井的施工方案。依据施工顺序,对沉井验算、沉井制作、沉井下沉处理施工的过程进行了详细分析。沉井施工工序较多,作业面狭小,下沉控制难度大,因此在施工时应特别注意工序之间的组织配合,以确保沉井施工质量。

Introduce a construction scheme, which includes equipment foundation casting machine open caisson in a casting plant. According to construction sequence, make detailed analysis on open caisson checking calculation, fabrication and the process of open caisson sink disposal construction. Due to many open caisson construction procedures, narrow operation surface and difficulty of sink control, therefore, special attention shall be paid to organization and cooperation of process during construction so as to ensure the construction quality of open caisson.

马鞍山长江大桥南锚碇采用沉井基础,沉井入土深度超过50 m,其施工采用"3次接高,3次下沉"的工艺:第1次下沉采用降排水措施,第2次下沉采用半排水措施,第3次下沉采用不排水措施。在沉井第3次下沉过程中,开启空气幕助沉,显著加快了下沉速度。沉井下沉期间,采用综合监控手段,保证了沉井顺利、精确下沉。实践证明,该桥所采用的沉井下沉方案科学合理,下沉到位后沉井几何姿态良好。

Open caisson foundation is adopted for south anchor of Maanshan Yangtze River Bridge with the buried depth over 50 m, and its construction adopts technology of“jointing for three times and subsidence for three times”: the first subsidence employs dewatering and drainage, the second subsidence half-drainage and the third subsidence no drainage. During the third subsidence of the open caisson, air curtain is started to assist subsidence, speeding up subsidence remarkably. During subsidence of the open caisson, integrated monitoring means are adopted to guarantee smooth and accurate subsidence of the open caisson. The practice proves that the subsidence scheme of the open caisson adopted for the bridge is scientific and reasonable, and geometric profile of the open caisson after subsidence is in place is perfect.

圆形沉井和矩形沉井是给排水工程中最为常见的两种沉井，与桥梁工程中的沉井相比，给排水沉井有其独到的结构特点。结合 ANSYS 软件计算结果及现场实测数据，分析了这两种类型沉井在初始下沉工况和下沉到位工况的受力状况。结果表明，自重荷载和局部支撑面积是控制侧壁竖向弯曲的重要因素，竖向刚度的突变导致井壁出现“缩颈”现象，在“缩颈”部位产生应力集中。合理地选择施工工艺，以及加强下沉阶段的施工控制措施可有效改善沉井结构在下沉阶段的受力状况，凸显沉井在受力性能和经济方面的优势。

Circular and rectangular caissons are the most common forms in water supply and sewerage engi-neering.Compared with the deep-water foundations of major bridge,the drainage open caisson has its unique characteristics.Combined the calculated results of ANSYS with the field data,such two types of open caisson sinking in the initial stage and the design position are analyzed in this paper.The results show that gravity load and the area of local support are important factors to control vertical bending stress.Because of the stiffness varying in vertical direction,sidewall appears a necking down phenomenon.It will lead to stress concentration when the caisson sinking to design position.Based on the results,a reasonable construction technology and proper control measures could effectively improve the stress conditions of the caisson structure.With a series of practical guidelines,the open caisson would have a great advantage in mechanical behavior,economically and technically.

结合黄河特大桥主桥主墩沉井的施工,介绍了卵石土河道下钢筋混凝土沉井与其他类型围堰方案的比选,以及沉井制作及下沉施工工艺,可为今后同类地质情况下的水下施工积累经验。

Combined with the construction on main pier open caisson of the grand main bridge of the Yellow River,this pa-per not only introduces the selection of reinforced concrete open caisson under cobble soil river channel and other types of cofferdam schemes but also construction craft on the fabrication and sinking of open caisson,which provides experiences for underwater construction of similar geological conditions in the future.

根据武汉鹦鹉洲长江大桥北锚碇大型圆形沉井结构特点与工程地质条件，结合施工现场沉降监测控制点的实测数据，采用大型有限元计算程序ADINA建立了三维计算模型，对沉井结构及其周围的地下连续防护墙进行了有限元分析，分析了沉井在下沉与封底过程中其结构自身的应力分布与变形情况，并探索了沉井在下沉过程中对周边邻近高层建筑与堤岸构筑物的影响。计算研究结果表明：沉井外围的地下连续防护墙主应力会随沉井的下沉而相应地增加，在沉井封底后其变形主要出现在上部和底部；而沉井在下沉过程中其结构底部的刃脚、十字隔墙、十字隔墙与环形井壁结合处均会出现较大拉应力；沉井的周边土体沉降量会随下沉深度而相应地增大。在沉井封底完成后测点的沉降理论计算值与实际监测值比较吻合，一般计算值较监测值稍小：二者的差值在邻近高层建筑的沉降控制测点为-1.22～-0.88 mm；而在附近的长江大堤处的关键测点为-1.27～0.64 mm。该计算模型对锚碇沉井下沉过程的沉降控制具有参考作用。

Given the structural features and engineering geological conditions of north anchorage large cylindrical caisson of Wuhan Parrot Cay Yangtze River bridges, combining with in-situ monitored data of some key points, three dimensional calculation modes of FEM are established with software ADINA to analyze stress and deformation of caisson structures and its adjacent diaphragm wall. The stress distribution and deformation of the structures are studied during the caisson sinking and its bottom sealing. The effects of caisson sinking on adjacent high-rise buildings and bank structures are also analyzed comparatively. The research results show that: the principal stress of diaphragm wall increases with the increasing of sinking depth, and its deformation appears mainly in its top and bottom after the caisson bottom sealing, the tension stress would be higher at its structure cutting edge, the middle of cross wall, the joints of cross wall and inner face of caisson well. The correspo