Constructing a Retaining Wall on Sliding Soils

Posted in: ENGINEERING-DESIGN, Allan Block, Wall Failures
The old retaining wall (which failed) was constructed on soils that were sliding downhill!  The rock was too deep to put the new retaining wall on the bedrock, so we drilled piers down to the bedrock to stop the hill from sliding and to support the new retaining wall.

This video shows you how to prevent a retaining wall failure when there are sliding soils!


Link to Photos of this project
Joseph Kowalski, P.E.
Current State PE Registrations

Laconchita Landslide

Posted in: Homepage, VIDEOS

From Wikipedia:

The village of La Conchita is along a portion of the coast prone to mudslides, and sits beneath a geologically unstable formation. In 1909, a devastating mudslide occurred approximately one-half mile north of the town, and in 2005 slides closed Highway 101 in both directions, trapping residents.

USGS Image of debris flow from 1995 Landslide

Sandwiched between a steep, unstable hillside (with the La Conchita Ranch Company situated on the plateau directly over the community), and the Pacific Ocean, La Conchita has been the site of recent major mudslides:

  • On March 4, 1995 at 2:03pm, a mudslide buried or damaged seven homes, injuring no one. After the main failure, the weather forecast predicted more rain for the following week.
  • On March 10, 1995, a debris flow occurred in the canyon west of the March 4 slide, damaging four or five more residences and a bananaplantation.
  • On January 10, 2005 at 12:30pm, a massive mudslide buried four blocks of the town in over 30 feet (9 m) of earth. Ten people were killed by the slide and 14 were injured. Of the 166 homes in the community, fifteen were destroyed and sixteen more were tagged by the county as uninhabitable.

La Conchita Ranch Co. was sued by those affected by the 2005 landslide. A settlement was reached, giving the plaintiffs the company's assets and $5 million.[4]

Tiered or Merged Retaining Walls?

When one retaining wall is constructed above another retaining wall, the two walls together are called a Tiered Wall System.  Tiered walls look like this:

When dealing with tiered walls, a retaining wall contractor will ask:
  1. How far apart are the walls?
  2. How high are the walls?
  3. Are they really two separate, independent walls?
  4. Do the two tiers of wall join and become one (merged) wall?                      
                                                                                  READ MORE ...

Retaining Wall Block Tolerance

Posted in: BLOCKS
This short article discusses retaining wall block tolerance: what it is, what are the limits, and what happens when blocks are manufactured "out of tolerance".

Segmental retaining wall blocks do not use mortar.  They are simply stacked one upon another.  Sometimes there are grooves, or lips, or pins or clips that align the blocks.  However, the blocks always rest one upon another.

Our past videos (like this one) and articles discuss the critical importance of getting your first row of blocks perfectly level.  The blocks must be level front-to-rear and side-to-side.  A perfectly level first-row of blocks will help make wall construction fast!   Unless .... the blocks are out of tolerance!

When blocks are "out of tolerance" it means that one side of the block is higher or lower than the other side.  You can see that this can cause big problems for these reasons ... Read More...

Stone Strong Retaining Wall Installation

Posted in: Stone Strong, How-To Videos