where to implement pressure meter tests

Question

where to implement pressure meter tests

killswitchengage (Geotechnical)

(OP)

1 Jan 20 17:51

Hi
Obviously when laying down boreholes for a slope stability problem they should be located outside of the zone that already moved ( meaning on a stable ground next to it ) , but where should the pressure meter test be located? inside the unstable mass or outside ?

GeoPaveTraffic (Geotechnical) · Answer 1 · 2020-01-01 22:17:54

Why would you drill outside the slide mass? What do you think you will learn drilling in that area?

Why would you run a pressure meter test?

Mike Lambert

GeoEnvGuy (Geotechnical) · Answer 2 · 2020-01-01 23:08:26

If you are using the test to determine the insitu Ko then you need to target the area of the slide plane which has the most horizontal stress. Near the centre or resisting side of the slide plane of a circular slide.

GeoPaveTraffic (Geotechnical) · Answer 3 · 2020-01-01 23:52:01

Why would you want to measure K0?

Mike Lambert

killswitchengage (Geotechnical) · Answer 4 · 2020-01-02 08:47:29

Borehole are to be implemented in stable ground for residual strength determination
We conduct pressuremeter test to design the solution be it pile sheet or tiebacks or whatever and no I am not looking for k0 especially since we are using Menard test which is not reliable for k0

GeoPaveTraffic (Geotechnical) · Answer 5 · 2020-01-02 15:11:12

I've worked on at least 100 landslides over the last 30+ years. Never saw the need for a pressure meter test of any kind. Explorations, laboratory testing, and analysis vary with each slide, but in general I find the following works best.

Drill several holes in cross sections perpendicular to the slope. Sample using a combination of SPTs and Shelby tubes.

Install inclinometers in a couple of the borings in the mid to lower part of the slope.

Once the depth of slide plane is determined from the inclinometers and the laboratory testing is done, create your stability model in software. I prefer UTEXAS, but other programs can work just fine.

Analyze the slope and modify your strength and water level assumptions until you achieve a FOS of 1.0. You now have a model of the current conditions.

Modify the slope in the model to increase the FOS. Rock buttresses often work well and be relatively inexpensive, but really depends on the situation. I normally shoot for a FOS of 1.25, i.e. a 25% increase in FOS. Sometimes less, sometimes more; depends on the risk tolerance of the client and how well I feel about the slope stability model.

Mike Lambert

killswitchengage (Geotechnical) · Answer 6 · 2020-01-02 18:14:28

Yes i am well aware of your method sir I am talking about using the pmt for solution design. You cannot shoot for a butresse where the slope under the roadway is very steep and consist of highly unstable soil and beyond that there is the sea. Especially since I am talking about a critical road

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