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SLOPE STABILIZATION, DRILLED SHAFTS & ARCHING CAPACITY OF CLAY SOILS

SLOPE STABILIZATION, DRILLED SHAFTS & ARCHING CAPACITY OF CLAY SOILS

SLOPE STABILIZATION, DRILLED SHAFTS & ARCHING CAPACITY OF CLAY SOILS

(OP)
Could anyone provide technical references with guidelines to evaluate effectiveness of a line of drilled shafts to stabilize slopes in clayey soils? In particular: Is there a way to establish the maximum, effective, pile spacing as a function of the soil parameters of wet clayey soils, such as the plasticity index? Or, is there a way to evaluate the arching capacity of clayey soils in terms of pile spacing and plasticity parameters?

RE: SLOPE STABILIZATION, DRILLED SHAFTS & ARCHING CAPACITY OF CLAY SOILS

Luis....as MOE333 notes, this is beyond Geotechnical 101, and unless you are doing this as an exercise toward becoming a geotechnical engineer, you should get an experienced, qualified geotechnical engineer involved.

RE: SLOPE STABILIZATION, DRILLED SHAFTS & ARCHING CAPACITY OF CLAY SOILS

(OP)
To moe333 and Ron,

Thanks for your response. I am trying to evaluate a proposal that requires timber lagging below the bench for the tieback of a soldier pile structure, all the way down to the slip surface of a failed slope. The argument in support for deep timber lagging is that the soil mass above the slip surfaced was remolded during failure and has no arching capacity remaining.

The soil involved is stiff clay with unconfined compressive strength of 2 k/sqft. I am not a geotech expert but cannot visualize that deep timber lagging is necessary to transfer the soil push to the pile structure. I cannot see the soil mass flowing through a curtain of 30 in diameter piles spaced 6 ft apart on centers.

Thanks again.

RE: SLOPE STABILIZATION, DRILLED SHAFTS & ARCHING CAPACITY OF CLAY SOILS

You really need to get another experienced geotechnical engineer involved. There are calculations that can be peformed to determine arching, but as pointed out, they are complicated and there are a lot of variable. This isn't somehting than can be figured out here.

Mike Lambert

RE: SLOPE STABILIZATION, DRILLED SHAFTS & ARCHING CAPACITY OF CLAY SOILS

(OP)
To GeoPaveTraffic (Mike?),

Thanks for your response. Would follow your recommendation. However, the practical approach may be to accept the proposed deep timber lagging, (altough it seems it is an over conservative solution, since it implies that the soil has no arching capacity).

Thanks again.

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