打入桩与桩疗 - 比较

Placing long piles in dense soils may be a time consuming endeavor with a traditional pile hammer and driving rig. Pile jetting offers significant time and cost savings over traditional pile driving, and where appropriate, jetting techniques could eliminate the need for a driving rig altogether. Pile jetting equipment usually consists of a crane with leads to place the piles, a jet pipe (or pipes) with connecting hoses, and a jet pump. Pile jetting can be used for most types of steel, wood, and concrete piles. Precast concrete piles may be fabricated with a jet-pipe already cast-in-place, if jetting is anticipated. Piles that are placed in uniform granular soils may be installed with a jet pipe placed through or near the center pile dimension. Other piles may have two water jet pipes fitted on either side to provide evenly distributed water jet coverage during placement. Design of the jet pipe outlet(s) and pump selection reflect the anticipated soil conditions and pile types.

The applied water pressure and flow rate through the jet pipe will directly influence the volume of sub-grade soils affected. Too much flow and pressure may result in poor controllability and alignment of the pile being worked, or misalign and compromise adjacent piles. Too little water flow or pressure could make the jetting technique ineffective. Thetype of soils支撑桩需要被evaluated和understood. The jetting technique creates a localized soil disturbance wherever it is used. Laboratory tests have shown pile jetting can significantly reduce the lateral strength of placed piles since the technique can erode fine soil particles from the surrounding soil matrix. Pile jetting is most effective in granular soils without significant cohesion (interlocking). Water run-off from the pump discharge hose, including erosion and turbidity control issues, is another factor that needs to be planned in advance.

最显著的挑战可能是堆喷射的任何负面影响将是潜在的。在一个典型的打桩工程中，使用公知的重量和下降高度的桩锤。注意到桩锤在指定的桩长击数允许桩强度的直接评估。相反，如果一个桩喷射到其最终尖端高程，其最终强度的能力可以凭经验估计为最好，但没有具体确定。

由于这些原因，越影响喷射成为投机，少推荐的技术越高。项目成本，完成项目的最终用途，和安全的因素会影响决定允许堆喷射，到什么程度。甲风险较小使用喷射的将是通过上面提供公知的轴承能力在最后桩端标高牢固基岩层硬沙质土壤。

这两种方法的结合s is another option. For example, a project engineer may specify that pile jetting may be used, but only through a specified pile tip elevation. This may offer some savings in time, but these would be offset by a requirement to mobilize both jetting equipment and a driving rig. A project specific cost analysis would be required. Some projects specify that pile jetting may be utilized, but the final 5-10’ must still be driven with a hammer and driving rig, which attempts to offer the advantages of both techniques at the construction contractor’s discretion.