Flexible, Cost-effective Jet-Grouted Deep Pile Foundation Alternative

Automates Capacity Assessment and Improves Scalability of Foundation Installation

This jet-grouted deep pile system combines the advantages of both driven and cast shafts to improve the flexibility of foundation installation. Most, if not all, heavily loaded structures or buildings on poorly conditioned soil are supported by deep foundations in order to distribute the structural loads deeper into the ground. Generally, deep foundations fall into two categories: (1) a driven pile, which can include timber, pre-cast concrete, steel, or pipes that are driven or vibrated into the ground; and (2) a case-in-place shaft, which is a hole constructed in the ground and subsequently filled with engineered materials. Both types of deep foundations have their own advantages and disadvantages. Researchers at the University of Florida have developed a jet-grouted deep pile foundation that combines the advantages of both driven and cast shaft foundational supports while minimizing or eliminating the disadvantages of each, providing a flexible and cost-effective alternative.

Application

A jet-grouted pile for deep foundations in both large-scale and small-scale projects

Advantages

• Provides scalable technology, facilitating use in both small and large scale foundation projects
• Automatically performs capacity assessment at the end of installation, eliminating the need for costly load testing equipment, instrumentation, and time delays
• Designers know the axial and lateral capacity of the pile at the design stage, providing significant economic savings over both driven piles and cast-in-place shafts
• Supports many material types and shapes, meeting the requirements of specific applications and load values
• Low startup cost and easy to use, providing a competitive advantage

Technology

There are several major components of the jet-grouted deep pile foundation: (1) the structural member, including an associated grout membrane; (2) the jetting pipes and nozzles; (3) the grout delivery and return system; (4) the grout mix design; and (5) the jetting and grouting process. The structural member carries the axial, lateral, and torsional loads from the structure. Attached to the outside of the structural member is a grout membrane that limits the outward expansion of the grout bulb and prevents soil contamination. The grout delivery system travels from the ground surface to the grout membranes throughout the pile and back to the surface. To accurately assess the grout pressure, UF researchers developed a grout stress gauge that uses an air bladder controlled value, glycerol/water fluid, and a pressure gauge. The grout mix increases flow ability and binding characteristics over typical compaction grout, thus ensuring good return pressures in small grout pipes.