×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Retaining walls tp support cut in solid rock

Retaining walls tp support cut in solid rock

Retaining walls tp support cut in solid rock

(OP)
I am in the process of planning a 100 ft long retaining wall to support grading for a new house of a sloped up lot. The height of the retaining wall ranges from 5 to 8 ft. The area is labeled as seismic and geo-hazard  as most of San Jose CA is. I am doing some exploratory digging on the land mainly for landscaping purposes and in some area I have to cut into the hill side to create flat terraces for the trees I am growing, this is giving me a great opportunity to learn about the geology of the land. Here are my observations:

1- Top soil is only 1 ft with plus or minus in some area.
2- After the top soil is cleared I reach solid bedrock which I can describe as continuous, by most by the time you reach 2 feet depth you are on a continuous solid bedrock.
3- The make up of the bedrock is very solid stones raning in size from small to huge all connected together by less solid material but very stable and require very hard chizzling or even power tools like a compressor with hammering jack to remove.
4- When you cut in the bedrock you expose a very stable cliff that in my opinion as strong as concrete. I thought I would like to keep this exposed since the colors of the stones exposed makes the look and feel a great thing and I believe the cliff is extremely stable and will never move.

What will I need to do to convince the city that I do not need a structural retaining so I can keep my view on the natural as exposed by the cut?

Many thanks

Aad  

RE: Retaining walls tp support cut in solid rock

Hire a local geotech that could advise you and the City on the pros and cons of your thinking.

Mike McCann
McCann Engineering

RE: Retaining walls tp support cut in solid rock

if that were here, rock coring would likely be required to evaluate the bedding, fractures, strength, etc relative to what is planned. the geotech would need to perform the exploration and evaluate the stability of such a wall for your locale. the house foundation location and loads relative to the wall will likley be a critical detail that the geotech will need to know (sure would hate to see the house end up like other houses i've seen on the nightly news where they fall off the side of a hill).

RE: Retaining walls tp support cut in solid rock

you say you have observed the geology, however no mention of:
a) type of rock / geologic units
b) quality of the rock (except for "strong as concrete")
c) location of any faults
d) bedding conditions
e) strike and dip
f) surficial topography

without an adequate investigation of the geology, there can be no reasonable conclusion drawn on the stability of your cliff.  you need a geologist

RE: Retaining walls tp support cut in solid rock

definitely get a geologist to map it for you, the city likely shouldn't accept anything without the mapping.

One thing you could do is to make a false cut 10 or 15 feet off of the proposed final edge and see what you have, get the geologist to map it, do some slope stability calcs etc., then cut it to final design if it is ok.  We have proposed to do that were there are questions about the geology, and you can't find everything with borings.

RE: Retaining walls tp support cut in solid rock


Get a certified engineering geologist (CEG) familiar with the area geology to first review the site with respect to the area geology.  You're dealing with the geology of the terrances acreted to the California coast, and in many cases, what appears stable is not.

Since you are cutting into slopes, although the cuts are relatively small, the potential impacts upslope should be well understood.  Let the CEG develop a scope of work to answer your questions.  It will go through your building official with more ease, and may save a lot of grief later on!  

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources