Handy Geotechnical Instruments, Inc
 

Ko Stepped Blade

Lateral stress (pressure) is one of the most critical measures affecting soil behavior—and almost never is measured! Why? Because until recently it has been too difficult to measure.

Research engineers worked for years to solve this problem, and so did we.


The main difference is that we came up with a proper answer


The Ko Stepped Blade uniquely solves the lateral stress problem by measuring pressures on a series of different steps. It gives DIRECT measures in a matter of minutes and WITHOUT any arbitrary correlations.

The Ko Stepped Blade can be used to determine the stability of an existing foundation or retaining wall, by measuring the mobilized lateral stress.


Ko Stepped Blade Graph


Lateral soil stress is like a detective story because it depends on stress history. For example,


  • Abnormally low, it means that a soil may collapse if saturated with water.
  • Abnormally high, it means that a soil is either overconsolidated or expansive.
  • Remnants of clay expansion pressure are shown to be retained over 100,000 years.

The change in lateral stress with depth can show how much soil has been removed by erosion.


Ko Stepped Blade chart


15 tests were performed in about one hour in a soft soil zone dislocated by a Rammed Aggregate PierTM, and confirm precision and accuracy of the Ko Stepped Blade. The friction angle is from Rankine theory and closely agrees with Borehole Shear Test data. Courtesy of the Geopier Foundation Co., Inc.


  • A 100 percent transfer of lateral stress over a distance means that at some time in the past a soil was liquefied by an earthquake or other vibrations.
  • A lateral stress that exactly equals vertical stress also means that at one time the soil was liquefied.
  • Increasing lateral stress at the bottom of a slope is the overture for a landslide; stand back or get out of the way.
Ko Stepped Blade Image 1

After the fall; a tragic end to four lives. This 10m (30 ft) high wall went up and came down with no engineering. Galena, Illinois.

Ko Stepped Blade Image 2

It is not just the soil under a foundation that holds a building up; it is the soil alongside that exerts lateral pressure and keeps soil underneath from being pushed out. Photo by Prof. J. M. Hoover.

Ko Stepped Blade Image 3

After a soil berm was removed from inside, soil pressure on the outside took out this 17m (55 ft) high retaining wall. Nobody got hurt but a lot of people were embarrassed, and it made some lawyers happy.

 
© 2017 Handy Geotechnical Instruments, Inc.