Geotechnical Failures

Why hire a Geotechnical Engineer?  To avoid problems such as the ones presented in the photographs below.

Every new construction project should have a geotechnical engineering evaluation.  Here are some thoughts for those considering ignoring a formal subsurface characterization study (geotechnical evaluation):

(1) It is a part of the normal "standard of care" to determine soil conditions before designing and constructing a foundation or pavement system.

(2) The Texas Section of the American Society of Civil Engineers (ASCE) "Recommended Practice for the Design of Residential Foundations" requires that "prior to foundation design, a geotechnical investigation and report shall be completed by a Geotechnical Engineer."

(3) The International Building Code (IBC) Section 1803 requires a soil investigation be performed for the design of new foundation elements except where waived by the "building official" if satisfactory subsurface information from adjacent areas is available.  Be careful on how you define "satisfactory".  The IBC also states "in areas likely to have expansive soil, the building official shall require soil tests to determine where such soils do exist."  Many areas in Central Texas are likely to have expansive clay soil, therefore a geotechnical study is be default required.

(4) Structural home warranty companies such as 2-10 HBW require a geotechnical evaluation for every house lot.  If a Builder does not have a geotechnical evaluation performed, they set themselves up for a conflict with the warranty company with regards to whom might have to pay for repairs.

(5) The post-tensioning institute (PTI) requires as stated in their Design of Post-Tensioned Slabs-on-Ground manual that "a single lot investigated in isolation should generally include 2 borings [...] a minimum of 20 feet in depth [...]"

(6) Pavement section thickness design is provided by a knowledgeable Geotechnical Engineer.  Without a geotechnical report, your pavement may not be designed to be reliably durable for the soil conditions at the site.

(7) The Association of Pool and Spa Professionals recommends site specific structural and geotechnical engineering for in-ground concrete or gunite swimming pools.
Engineers are responsible to the public and to the Texas Board of Professional Engineers.  For examples of enforcement punishment related to engineers who have skimped on geotechnical evaluations or have made mistakes related to inspections or design, visit:


If you are an Owner, Developer, Contractor, Subcontractor, or Architect, please realize the permanent burden of responsibility put on engineers before considering their work "too conservative" or as we prefer to say "safe".  "Safe" and "engineering" are supposed to be synonymous.  The alternative is just plain reckless.  Unfortunately, with limited budgets, engineers already work at the margin of safe and risky.
 

This was a part of the infamous retaining wall failure in San Antonio that damaged many homes that were above the wall system.  Retaining wall failures are caused by any number of conditions such as:

- The design earth pressure was not reasonably estimated, or even worse the wall was not engineered and the as-built c
condition did not account for the proper earth pressure.

- The wall design did not account for hydrostatic water pressure (wall system not properly drained, or drainage system not maintained).

-The wall design did not account for sloping soil above or below the wall.

- The wall design did not account for swelling clay backfill behind the wall.

- The wall design did not account for settlement of the wall footing.

- The anchored wall (i.e. soil nails, pre-stressed anchors) did not have anchors adequately embedded.

- The wall design did not account for surcharge loads above and behind the wall.

- The wall design did not account for global slope stability (i.e. geotechnical analysis).

This is another image of the San Antonio wall failure.

 

This is an example of a gabion wall failure.

 

RETAINING WALL FAILURES

 

Another retaining wall failure.  Appears to be a local stability failure of a segmental block retaining wall (or improper reinforcement detailing or installation), therefore this is more of a structural failure than a geotechnical type failure.

 

A retaining wall failure instigated a landslide that covered this busy street in New York City area.

 

This was an MSE wall failure apparently caused by expansive clay backfill or native cut face behind the backfill zone exerting earth pressure exceeding value used in design.  Photo by Paul Spraggins of TxDOT.

Here is a terraced retaining wall system that failed, most likely due to a lack of an engineered design.

In May 2014, Baltimore, Maryland, an apparent mortared stone block retaining wall (gravity wall?) failed after heavy rain, causing pavement and parked cars to fall and debris covered the nearby railroad track.  There is a video of the collapse from a witness standing in front of the townhouses (find it on youtube).

This segmental block retaining wall in Roanoke, Virginia, experienced a partial failure, likely related to saturation of the backfill (poor drainage).  The designs and construction QC of notably tall retaining walls should be checked and double-checked.

SETTLEMENT FAILURES:

 

This is a picture of a high rise building being demolished in South Padre due to poor geotechnical design that led to ridiculous amounts of settlement.  Read about it more here:

South Padre Building Settlement

Lakeport, California, 2013.  Approximately 20 homes are abandoned after fissures and settlement of up to 10 feet destroy homes and make subdivision worthless.  Quick but progressive settlement from March to May.  In this photo you can see some of the fissures in the background.

Bearing capacity failures are rare but do occur.  This is a photo of an infamous grain silo collapse that every geotechnical engineering student learns about when studying basic bearing capacity equations.

EXCAVATION BRACING FAILURES:

 

This is a distressed street area adjacent to a failed pier wall bracing system (to left).  Urban excavations require rigid bracing to limit or prevent movement behind the wall.  This system obviously was not properly designed or constructed.

Here is a photograph of that pier wall, with new bracing installed to prevent further movement.

Here is another pier wall that deflected excessively (failed) at the lower elevations and required a quickly constructed soil berm to prevent further movement.

Here is an image of a failed soldier-pile and wood lagging excavation bracing system in 1984.  Global instability failure due to system embedment being too shallow is the likely cause.  Note vertical scarp face in front of street and behind wall.

ROCKFALLS and ROCK SLOPE or BLUFF STABILITY:

 

Vertical or near-vertical cut faces in limestone rock materials are not stable over the long term.  Wedge-type failures, planar-type failures, and shallow sloughing failures will periodically occur as seen in this photo as the exposed surface is subject to weathering processes.

A limestone bluff failure occurred in Lake Whitney in Texas in 2014.  The exterior covered patio collapsed with the failed rock mass and the house had to be abandoned and demolished by burning.

Here is another view of the Lake Whitney failure.  Appears to have been a large wedge-type failure.  Do not construct homes near bluffs, particularly without a geotechnical engineering site evaluation.

Another view of the Lake Whitney site.  Note the fracture (fissure) exposed at the surface of the rock mass.  The bluff is not vertical but worse is recessed underneath the top (concave inward).  The rock mass in front of the house in this photograph is close to imminent failure and will collapse as well.

This is a wedge-type rock slide that occurred in North Carolina.

This is a large toppling failure of sedimentary rock in Normandy, France, that was caught on video by a bystander in 2013.  Luckily no one was on the beach downslope of the rock bluff.  Do not build grade-supported structures at the top of a bluff unless you accept the risks.

In 2008 a large apparent rock toppling failure occurred in Cairo, Egypt, tragically killing over 100 people in the developed area below the vertical rock face.  Local geologists had already predicted the hazard:

http://engineering.kau.edu.sa/Files/135Researches/59067_29414.pdf

Rockfall hazards exist anywhere there is a vertical or steep slope face in rock materials without any man-made protection.  Buffers or other mitigation measures are required when constructing roads, parking lots, or structures near the base of steep cuts in rock geology.

EXPANSIVE CLAY SOIL PAVEMENT FAILURES:
(see also pavement cracking page)

 

The City of Hutto reconstructed some of their downtown streets in 2005-2006.  The design and construction ignored the geotechnical recommendations concerning subgrade improvement (due to cost), and the results were predictable (expansive clay cracking the streets), much to the chagrin of the complaining populace.

This is what happens when you place concrete pavement on expansive clay soil without proper detailing recommendations by a Geotechnical Engineer (or at least one who is experienced and understands how to handle this environment).  This is not a joint, this is a large crack within the panel that is exhibiting both crack faulting and separation cracking.

OTHER TYPES OF GEOTECHNICAL FAILURES:

 

Ok, so this happened in China and not the USA, but still a wake-up event.  A high rise building under construction (near completion) collapsed due to a soil related failure.  Temporary excavation adjacent to the structure on one side, and temporary spoils piles on the other side, helped induce forces adequate to shear the pile foundations, cause global slope instability, and cause the collapse.

A bulging CMU basement wall can occur if the wall was not designed for the proper soil-related design parameters (retaining wall design) and drainage considerations.

This was a cheap single-block width screenwall at the Sunfield development in Buda, subsequently torn down because of failures, that was placed on expansive clay soil.  Screen walls, retaining walls, pavement, must all be engineered (Structural Engineer, Geotechnical Engineer), otherwise you risk experiencing costly failures and replacement work.

Culvert outlet pipe cantilevers over a failed slope at discharge point (presumably).  Be careful how you design and construct discharge points on slopes.  This may have started as an erosion problem and then a slope stability problem.
SLOPE STABILITY FAILURES:

 

Here is a slope failure that occurred in north Austin on IH-35.
2017 landslide at Big Sur in California, destroying a segment of Hwy 1.  Appears to be a planar type failure in rock geology.  The geology is mixed in that region.  The extreme topography and significant annual rainfall make the area prone to landslides.  A nearby bridge had to be demolished because its concrete pier-columns were displacing due to the piers bearing in landslide material at the base of the valley.
Here is another example of a landslide global slope stability failure.
This is the 2007 San Diego (La Jolla Mt Soledad) global slope instability failure.  Geology appears to have been inter-bedded siltstone, sandstone, and shale.  I speculate a progressive loss of shear strength due to groundwater (from irrigation, water line or sewer line leaks, and other sources) and cycles of wetting and drying.  A concrete drilled pier secant wall was installed to stabilize the slope.
Here is another view showing the destruction of the local street by the slope failure in San Diego.
This is a shallow slope stability failure in clay soil along a roadway embankment (IH30 west of Walton Walker Blvd) in Dallas.
This is a global slope instability failure that occurred in Everett, Washington State.  The back side of the house fell with the slide.
This is an infamous 2010 rock slide in Taiwan.  The rock formation had a dip-slope at the highway cut and voila, massive failure.
Here is the opposite view of the same rock slide.
In 1999, Hole 18 at a California golf course, soon to be purchased by Donald Trump, slid towards the ocean.  The area geology indicated a previous slide  that was identified as Landslide C.  One hypothesis included a leaking city sewer line and a thin layer of bentonite clay near the base of the slide.  
...The reconstruction consisted of a massive MSE type internal wall-butress with up to 95-ft long reinforcement geotextile high strength fabric. 
This was a wide and long global instability failure (landslide) that occurred in Saint-Jude, Quebec in 2010.  
In March 2012, a landslide (global slope instability) failure occurred in Puget Sound in Washington State.  Luckily no one was killed.  The collapse was heard up to 8 miles away. 
Here is another photograph of the Puget Sound landslide.  One can speculate that a geotechnical engineering study of 2D slope stability conditions could have predicted this failure based on the slope geometry and soil type.  Notice how far the road was shifted downslope and note the soil and tree mass out into the water.  
In March 2014 a global slope instability failure occurred in Washington State, killing dozens of people.  A suspected fine-grained soil condition and groundwater (saturation) from recent rainfall likely led to a low shear strength and subsequent failure.  Transported soil mass with groundwater entered river water to create a mudslide that exacerbated the spread.  
Here is a closer view of the same slide and the upper portion of the failure surface.  
This shallow global slope instability failure or landslide occurred in Dallas, Texas.  Notice the shotcrete surface repair was worthless as progressive sliding occurred.  
View of the 2010 landslide in Italy.  There is video of the landslide occurring.  Heavy rainfall saturated the soils and reduced shear strength to low levels.    
Here is a wider view of the Italy landslide.    
House site in NY State damaged from global instability failure in 2011.  No, those columns are not supposed to be diagonal.  
2014 in North Salt Lake, a slope stability failure occurred upslope of this house (landslide into house), causing irreparable damage and partial collapse.  Notice the scarp face at the top of the slope.    
This is a photograph of the reinforced slope constructed at Yeager Airport in West Virginia (soil fill with horizontal geosynthetic reinforcement).....    
... and this is a photograph after the slope failed in 2015.  The slope was approximately 74 m tall (243 feet) and the geosynthetic reinforcement was supposedly 144 to 174 feet wide.  Miragrid 20xt and 10xt were apparently used.  Not sure what the vertical spacing might have been.    
...and here is a wider view of the slide.  A forensic study was in progress and we understand one of Mr. Kauffman's professors at Virginia Tech is assisting with the case (Prof. Brandon).  This reinforced slope was engineered but it is not clear what role any geotechnical engineers had in the design of the slope and reinforcement details.   
A landslide occurred in La Conchita, California, in 1995......    
...and again in 2005, this time with fatal results.  Landslide-prone geology and topography and drainage conditions must be respected and properly considered before site development or permitting site development.    
This house in Camden County Missouri experienced severe settlement due to global slope stability failure along the lake. The house split into two along a central pivot alignment.    
    2014, near Colbran, Colorado.  A landslide occurs, initiated by a global slope stability failure (rotational) in sedimentary deposit rock formation material near the top of the mountain.  The debris landslide occurred after notable rainfall and traveled approximately 2.8 miles, killing 3 men and leaving new deposits up to 150 feet thick in a matter of minutes (not millions of years).
2015, Colorado Springs, slope instability failure in hillside previously identified as a landslide risk area produces scarp that undermines the edge of a house. 
2009, Nachterstedt, Germany.  Landslide kills 3 as one house is sheared in two with half collapsing downhill.    
SOIL PIPING FAILURES:

 

2010 Milwaukee.  This sinkhole formed as a result of a leaking or broken sewer pipe that allowed loss of soil through pipe and eventual collapse of the street above.    
This apparently was a sinkhole induced by soil piping (water induced) or collapse into an abandoned zinc or lead mine tunnel in Picher, Oklahoma in 2008.    
Ever see a dam outlet pipe fail?  This was most likely due to a soil piping failure around the outlet (hydraulic gradient of seepage too high).   
This sinkhole in San Antonio, Texas, in 2016, claimed the life of one person.  The sinkhole appears to be due to a soil piping failure (storm sewer line break?).    
NATURAL SINKHOLES:

 

This was a massive sinkhole in Guatemala in 2007.  Sinkholes in limestone formations may or may not be identifiable from geotechnical borings, but it is better to perform the geotechnical study than not.  There are certain indicators that can hint to the possible presence of a developing sinkhole before it is too late.    
This is a 2008 sinkhole in Daisetta, Texas, that formed in a salt dome material (soluble similar to limestone).    
This 2013 sinkhole in Guangzhou, China, appears to have formed naturally in karstic limestone conditions and swallowed a 2 and 3 story building.    
This sinkhole reached the surface in August 2013 and caused the collapse of a resort hotel building.  Luckily noises from strain in framing alerted the occupants that something was going on and they were able to escape before the collapse.