How to Select Proper Pile Type?

The purpose of a pile foundation is to transfer and distribute load through a material or stratum with inadequate bearing, sliding or uplift capacity to a firmer stratum that is capable of supporting the load without detrimental displacement. A wide range of pile types is available for applications with various soil types and structural requirements. So before we delve deep into selection of appropriate type of pile, let’s have some idea regarding some common pile types and their features.

Features of Common Pile Types

(1) Steel H-Piles

在另外一些钢铁H-piles显著的优势er types of piles. They can provide high axial working capacity, exceeding 400 kips. They may be obtained in a wide variety of sizes and lengths and may be easily handled, spliced, and cut off. H-piles displace little soil and are fairly easy to drive. They can penetrate obstacles better than most piles, with less damage to the pile from the obstacle or from hard driving. The major disadvantages of steel H-piles are the high material costs for steel and possible long delivery time for mill orders. H-piles may also be subject to excessive corrosion in certain environments unless preventive measures are used. Pile shoes are required when driving in dense sand strata, gravel strata, cobble-boulder zones, and when driving piles to refusal on a hard layer of bedrock.

(2) Steel Pipe Piles

钢管桩可能是开口或封闭端的，并且可以用混凝土或未填充。混凝土填充管桩可以在某些情况下提供超过1000千克的负载能力。

Installation of pipe piles is more difficult than H-piles because closed-end piles displace more soil, and open-ended pipe piles tend to form a soil plug at the bottom and act like a closed-end pile. Handling, splicing, and cutting are easy. Pipe piles have disadvantages similar to H-piles (i.e., high steel costs, long delivery time, and potential corrosion problems).

(3) Precast Concrete Piles

预制混凝土桩通常预应力withstand driving and handling stresses. Axial load capacity may reach 500 kips or more. They have high load capacity as friction piles in sand or where tip bearing on soil is important. Concrete piles are usually durable and corrosion resistant and are often used where the pile must extend above ground. However, in some salt water applications durability is also a problem with precast concrete piles. Handling of long piles and driving of precast concrete piles are more difficult than for steel piles. For pre-stressed piles, when the required length is not known precisely, cutting is much more critical, and splicing is more difficult when needed to transfer tensile and lateral forces from the pile head to the base slab.

（4）铸造混凝土桩

Cast-in-place concrete piles are shafts of concrete cast in thin shell pipes, top driven in the soil, and usually closed end. Such piles can provide up to a 200-kip capacity. The chief advantage over precast piles is the ease of changing lengths by cutting or splicing the shell. The material cost of cast-in-place piles is relatively low. They are not feasible when driving through hard soils or rock.

(5) Mandrel-Driven Piles

心轴驱动的桩是用心轴在地面驱动的薄钢壳，然后用混凝土填充。此类桩可提供高达200克利普的容量。缺点是这种桩通常需要获得专利，用于安装和安装的特许经营系统并不像钢或预制混凝土桩那么简单。它们提供较小的钢成本的优势，因为可以使用较薄的材料而不是顶部驱动桩的情况。沉重的心轴使能力很高。

Mandrel-driven piles may be very difficult to increase in length since the maximum pile length that can be driven is limited by the length of the mandrel available at the site. Contractors may claim extra costs if required to bring a longer mandrel to the site.

（6）木材桩

木材piles are relatively inexpensive, short, low capacity piles. Long Douglas Fir piles are available but they will be more expensive. They may be desirable in some applications such as particular types of corrosive groundwater. Loads are usually limited to 70 kips. The piles are very convenient for handling. Untreated timber piles are highly susceptible to decay, insects, and borers in certain environments. They are easily damaged during hard driving and are inconvenient to splice.

选择适当类型的桩

Preliminary Selection of Pile Type

All identified foundation alternatives should first be evaluated for suitability for the intended application and cost. For piles, this evaluation should be based on the容量那可用性那constructability那and expectedperformance各种类型的桩。非桩替代方案的初步评估应基于类似的标准。这将限制进一步的研究，这些替代方案是合理可行的。在该初始评估期间，也可以从考虑到明显的高成本替代方案来消除。

（1）负载能力和桩间距

Of prime importance is the load carrying capacity of the piles. In determining the capacity of a pile foundation, it is important to consider the pile spacing along with the capacity of individual piles. The lateral load resistance of the piles may also be important since lateral loads can induce high bending stresses in a pile.

（2）构造性

必须考虑预期地下和表面效应对结构的影响。在硬驾驶中易受损坏的桩不太可能穿透硬层或砾石和巨石区域。在施工期间的驾驶振动的土壤干扰或传输可能会损坏相邻的桩或结构。必须选择桩间距和争斗，以防止在驾驶期间干扰其他结构部件。18新利官网登录在线切割或拼接堆的易容易性也可能影响结构性。

(3) Performance

桩基必须以设计的寿命为设计。可以在结构位移方面描述性能，这可能与作为实际桩故障的结构一样有害。由于桩材料的劣化，负载容量不应随着时间的推移降低。

（4）可用性

Piles must be available in the lengths required, or they must be spliced or cut off. Project scheduling may make lead time an important consideration, since some piles may require up to 6 months between order and delivery.

（5）成本

一旦绒毛型满足所有其他标准，相对成本就成为了主要考虑因素。为了比较桩的类型，可以足以比较每个负载能力的桩成本。单位容量成本之间的比较可能导致某些桩类型的明显排除。成本评估应包括与桩基相关的所有有关的费用。这种成本可以包括储存或拼接的额外费用。它们可能包括用于减少升压压力的压力浮雕系统，从而控制桩载荷。此外，应包括在比较成本估算中的任何所需修改以容纳桩。例如，可能需要增加基板厚度的厚度以为桩的顶部提供额外的嵌入。

最终选择桩型

最终的评估和选择应主要基于其余替代品的相对成本。该评估应包括适应基础类型所需的结构或场地修改的成本。成本和其他因素在选择中可能很重要。可以考虑交付或安装时间表的差异，性能可靠性和潜在的施工并发症。

When comparing a pile foundation to another type of foundation, it will be necessary to develop a preliminary pile layout to determine a reasonable estimate of quantities.