深水基础套箱围堰施工综述.rar

一、围堰的类型
目前，围堰主要有以下几种：钢板桩围堰、混凝土围堰、钢套箱围堰以及钢-混凝土组合结构围堰。其中，钢板桩围堰主要为单壁结构；混凝土围堰又分为重力式钢筋混凝土围堰和双层薄壁钢筋混凝土围堰；钢套箱围堰又分为单壁、双壁以及单双壁组合式钢围堰；钢-混凝土组合结构围堰也可分为上钢下混凝土、下钢上混凝土形式。每种围堰都有自己的特点和适用条件，因此需根据各自的水文、地质、材料价格以及设备情况等比选而定。下面分别就每种围堰的结构形式及适用条件结合实例加以综述。

二、钢板桩围堰
钢板桩围堰是一种比较传统的深水基础施工方法。钢板桩是从国外引进的一种制式产品，我系统主要为德国拉森式钢板桩。钢板桩可以打入上中或连到物件上，组成承载及防水结构，工作结束后，拔出或拆下重复使用。
1．结构型式及特点
钢板桩围堰一般采用单壁的矩形、圆形等结构形式，内部根据水位情况设置支撑，该围堰因为是重复使用，因此，一般没有封底混凝土；它是一种施工简单、快捷、成本较低的围堰形式。但是，该围堰也有其很大的局限性，其一，由于是组拼式结构，整体刚度较小，因此其抗水流及冲刷能力差，不宜于在流速较大的情况下使用；其二，由于其本身强度、刚度局限，在承台较深时，需设置强而密的支撑，对后续的承台及墩身施工干扰很大，因此，不宜于在水位较高的情况下使用；其三，因为要重复使用，不宜灌注封底混凝土，因此，在既要满足底部支撑力，又要满足较小渗流的情况下，对河床提出了较高的要求，因此，不宜在透水性强，承载力小的地层条件下使用。
2．施工工艺及施工要点
（1）施工工艺流程（图1）
First, the type of cofferdam
Currently, the main cofferdam the following: steel sheet pile cofferdam, cofferdam, cofferdam of steel sets and steel - concrete composite structure coffer. Among them, the steel sheet pile cofferdam is mainly single-walled structure; concrete cofferdam was divided into Gravity and double reinforced concrete thin-walled reinforced concrete cofferdam cofferdam; steel boxed cofferdam was divided into single-wall, double wall and single and double wall modular steel cofferdam; steel - concrete composite structure can be divided into the upper cofferdam of steel in concrete, the concrete forms of steel. Each cofferdam has its own features and application conditions, so be according to their hydrology, geology, materials, prices and equipment in the election may be geometric. The following are the structure on each cofferdam and the applicable conditions to be reviewed with an example.

Second, steel sheet pile cofferdam
Steel sheet pile cofferdam is a more traditional deep foundation construction method. Imported steel sheet pile is a standard product, I system is mainly for the German-Larsen, steel sheet pile. Steel sheet pile can enter on or connected to the object, the composition of the Bearing and waterproof structure, after the pull out or remove the re-use.
1. Structure type and characteristics
Steel sheet pile cofferdams generally use single-walled rectangular, circular and other structural form, set the internal situation under the support level, as is the repeated use of the cofferdam, therefore, generally do not cover concrete; it is a construction of simple, quick and cost more the form of lower cofferdam. However, the cofferdam has its many limitations, first, because it is assembling structure, the overall stiffness of smaller, so water and the erosion of its anti-poor, not at large in the flow conditions; second , due to its strength and stiffness constraints, deep in the cap, the need to set a strong and close support, and follow-up caps and large piers during construction disturbance, therefore, not appropriate for the circumstances under which the higher level; Third, because re-use, not perfusion back cover concrete, therefore, it is necessary to meet the bottom of the supporting force, but also to meet the low flow situation, on the river bed raised high expectations, and thus, not strong in the water permeability, capacity under the conditions of the use of small strata.
2. Construction techniques and key points
(1) construction process (Figure 1)