In-Cap Method

A Method to Strengthen Pile Foundations against Earthquakes Combined with Ground Improvement

The In-Cap method strengthens existing pile foundations against earthquakes with solidification improvement. Sheet piles are installed to the required depth around the existing footings, the ground within the sheet piles is improved by solidification using a high-pressure jet mixing method, and the existing footings and sheet piles are integrated with extra footings to create a reinforced structure. The In-Cap method was developed by a joint research group “Ground and Foundations 21” set up by three companies: Oriental Shiraishi Corporation, Nittoc Construction Co., Ltd., and Fudo Tetra.

Structural Outline


In-Cap has the following benefits over conventional methods of adding piles:

  • Underground wall around existing footings can also be used as a retaining wall when excavating, reducing the need for temporary earth retaining work.
  • Installing large-diameter piles or other construction work with low head-room is reduced or eliminated.
  • Quantities of steel frame and concrete for additional footings can be reduced.
  • Installation takes up minimal space, so little traffic regulation is needed during the work.
  • The above benefits make possible cost reductions of 30% and schedule reductions by 50%* (* based on one set of test results)

Additional Pile Method

In-Cap Method

1 Underground wall of steel sheet piling installed around existing footings solidification improvement

2 High-pressure jet mixing method used to harden ground within underground wall

3 Ground inside wall dug out to base of footings, and existing footings and wall integrated with reinforced concrete

4 Top of steel sheet piling is cut away, and infilled to ground level