Swimming Pool in bedrock on hillside

[aayjaber]

Planning a swimming pool to be placed in competent bedrock on a hillside location. The pool will be cut into perfect stable rock; this data is confirmed from adjacent excavations while creating landscaping planter. Is it better to cut the exact size of the pool and when placing reinforced concrete use the exposed rock face as a form for pouring concrete from one side and a wooden or metal form from the other side, or cut an additional 2-3 ft more than the pool footprint and build the pool walls with wood or metal forms on both sides then do and an engineered fill and compact it?

 

[civilperson]

If competent rock, why not smooth it with 3 or 4 inches of shot crete and forget the forms?

 

[aayjaber]

This is a good suggestion, I will tell the structural engineer to try this if that can pass the review by the City.

 

[STVU]

Have you met the H/6 setback? Also check with a local soils engineer about creep with that formation.

 

[BigEasyGeoSleuth]

I would also give some consideration to presence of daylighting bedrock discontinuities in the proposed cut slopes.

 

[geotekker]

Site Grading Plan Conflict

We have begun to see the following note on some site grading plans "All grading activity shall be coordinated with the recommendations in this report", referring to the site specific geotechnical report. However, the site grading notes further state the geotechnical report is "available for information purposes". We, the geotechnical engineer, contend that the report is not a contract document, is indeed for information purposes (in the hands of a contractor) only, and should not be used as a substitute for a project specific site grading plan. ARe we over-reacting?

 

[InDepth]

You may want to ask about the rock fracture plans. If there are fracture plans you may want to drill a few rock anchors. Shotcreting against the rock, using it as a backform, is a great idea....just don't forget the drainage strips and water proofing.

 

[aayjaber]

Rock Joints are well understood and documented by excavation of the one foot or so of top soil and gravel. There are joints that range in width from 3 to 8 inches on the surface and the good thing they tend to close down as you dig down. The frequency of the joints are at almost 8 ft. The joints run parallel with the direction of the slope which makes the rock formation stable.

If any rock joints persist after full excavations I will jet clean the joints and join the rock with epoxied 1 inch rebar and may grout the cleaned joints.