Deep foundations are perhaps the most robust option for supporting a structure. Sure, there are other options — shallow foundations (spread footings), intermediate foundations (aggregate piers) and ground improvement methods — but none are as impressive in their own right, or carry a load like a pile. Besides, piles provide so many options of their own that there’s insufficient room here to discuss anything else.

Deep foundations are more than we can handle in just one blog post. So, in this first part of our blog series, we will discuss the different types of deep foundations and some of what goes into designing them.Part 2将解决质量控制和完整性测试 - 换句话说，建设。

什么是深层基础，何时使用？

深层基础（普遍称为桩）是长，细长的，结构元件，其通过在深度支撑介质或支撑介质（土壤和/或岩石）中通过结构（建筑物，桥接，路堤等）来转移负荷。几何上，可以将深基坑定义为具有明显大于其宽度的长度（嵌入深度）。

深层基础可以钻，驱动，拧入或推入地面。在某些情况下，它们实际上是用手或典型的土方设备挖掘，然后用混凝土铸造以填补挖掘。由于许多原因使用深层基础。最常见的包括：

• Penetrating relatively weak, near-surface soils
• 穿透高度可压缩的土壤，例如有机物或深度弱粘土
• Penetrating deep, contaminated, near-surface soils
• Penetrating deep, uncontrolled fill
• Accommodating large loads

One can classify deep foundations in many ways based on their purpose, type, construction method, displacement or capacity. The table below is not an exhaustive list, but does cover the most common deep foundation types in the Midwest. In addition to material strength and diameter, typical load capacity also varies with subsurface conditions at the site. This concept leads us to the design of deep foundations.

深基础设计

如今，大多数深层基础设计方法都由联邦公路管理局（FHWA）发表，他拥有进行研究和现在的资源。承包商和材料供应商还推进了深基础设计，通常通过各种基于行业的社会或团体。

在概念中，深层基础的设计相对简单。桩的侧面通过桩和土壤之间的摩擦提供负荷的抵抗力。桩的底部通过轴承提供抵抗载荷，如典型的展开（浅）脚。然而，工作中的机制在实践中更复杂，特别是由于土壤和岩石行为的性质以及土壤和岩石的固有变异性。当您在压缩负载增加桩支撑时加入张力，移动和横向载荷时，桩的容量的评估和右桩型的选择变得更加困难和迭代。

Deep foundation design starts with understanding the subsurface conditions on a project site, as well as knowledge about what is to be built, the performance expectations and risk tolerance. Once subsurface conditions and building loads are established, suitable pile types for design can be selected based on how easy or difficult the installation will be. For example, driven piles or auger-cast piles may not be appropriate for a site where bearing soils contain cobbles and boulders mixed with weak or even competent soils. Likewise, drilled shafts may not be the best choice for a site with contaminated soils, the disposal of shaft spoils being potentially costly and difficult.

在识别合适的桩类型之后，下一步骤是评估不同桩类型的侧面和端轴承电阻以及长度，宽度和直径的范围。该评估包括开发地下条件的模型，并分配土壤或岩石强度参数，影响不同类型桩的摩擦或承载能力。

With the models developed, we next consider the different limit states to which the pile is subjected, such as strength in axial compression and tension, or settlement and lateral deflection. The project is then adjusted based on the results from the limit state evaluations, pile size, length or strength required to meet the performance, and the risk requirements of the project.

虽然它最有可能在整个步骤中进行，但与项目团队（所有者，结构工程师和承包商）的沟通现在达到了关键点。该团队需要评估不同桩类型的成本和性能。

在Br雷竞技好Newbee赞助商aun Intertec，我们喜欢查看负载支持成本，这是安装桩的成本除以桩的允许负荷。这与比较不同桩类型或尺寸的每英尺的成本不同。有时，安装更少，更长的桩更具成本效益，而不是安装更多，更短的桩。根据讨论的结果，本集团可选择考虑额外的桩类型或尺寸或消除一些考虑因素。希望这支球队能够识别完美的绒毛型和尺寸，可以移动到下一步的过程，建设，我们将在下周讨论第2部分。