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Slope failure prevention

Slope failure prevention

(OP)
My family has property located in the lower floodplain adjacent to a large creek in southern Alberta. The previous owner built a house close to the natural slope roughly 50-70 vertical ft high.
This winter/spring being exceptionally wet, a good chunk of the hill slid, destroying the inadequate retaining wall already built.

Now the new plane of failure exists beyond the property line, which is located roughly half-way up the hill.  We are looking for cost-effective ways to prevent the hill from sliding further.

Assuming excavation to reduce the slope steepness is not an option (dealing with an unfrieldly neighbor), what would you recommend to hold the slope?

The space between the toe of the current slide and the bldg is between 10-20 ft, further reducing options.

Please help

RE: Slope failure prevention

Has there been any dialog with the neighbor?  After all part of their slope is affecting the integrity of your family's property (unless I'm missing something).

f-d

¡papá gordo ain't no madre flaca!

RE: Slope failure prevention

  A little bit difficult to evaluate without sketches but horizontal drain holes to drain the side of the hill always improves stability.

You could spend quite a lot on geotechnical evaluations or  just commit to improving drainage.  Not wanting to get into discussions on global warming / changes to weather patterns , but alberta/ saskatchewan / manitoba sure seem to be getting highner levels of moisture to deal with in recent years.

RE: Slope failure prevention

As fatdad indicates drainage is usually the requirement.  That is easier said than done.  However, immediate work wold be to divert surface water away from the failure area.  I have even seen it necessary to place a tarp over the area to divert rainwater.

Some indication of water carrying soil layers in the slope may be evident and if so that may be a clue as to where any internal soil drainage is best placed.

If you have not already done so, this type of fixing usually requires a geotechnical investigation with test borings, possible tests and perhaps some slope stability calculations.

The construction of special internal drainage usually would involve specialty contractors,since most general contractors are not equipped nor do they know how.  This is a difficult thing to fix in most cases.

Finding suitable contractors might be done with an Internet search under such topics as: "Horizontal drainage; slope correction drainage; deep soil drainage".  But first a geotechnical engineer in the business probably is a worthwhile start.  Then a fix plan can be developed.

I'd document every thing, weather conditions, phone calls and with photos that include reference stakes, etc.  This may well be into court some day.  Keep a diary.  Even some simple reference stakes on the slope to monitor for movement may be helpful.

RE: Slope failure prevention

Similar to other comments, get a good experienced geotech firm involved to do an appropriate assessment.  This is a common problem around rivers/creeks in Alberta (remember a few years ago homes in Edmonton falling into the North Saskatchewan river).  I've seen lots of attempts at using physical stabilization without knowing the extent of the problem, and usually those fixes don't last.  I've been involved with a couple of these, and typically, the problem is deeper than expected (deep-seated failure mechanisms).

Likely the best fix, as suggested by others, is to try to control the groundwater.  Also if there are tension cracks, make sure to prevent water from getting in them - re-direct surface water, and if possible, try to re-grade the area (flatter, not steeper) to try and seal up those tension cracks.  They are a quick way for water to get into the problem soils, and cause additional movement.

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