horizontal drains may be the appropriate solution

thanks a lot sir , the piezometer test was conducted yesterday the soil is saturated

shale weathers to residuum, the friction angle of (many) shales and their residuum contimues to degrade (think decades) to a fully-softened value. Proceedures to obtain the fully-softened shear strength of shale (and shale fills) include the mechanical disaggregation of the shale (think blenderization) and direct shear testing on a slurry prepared to the liquid limit (think normally consolidated strength). You just have to normally consolidate the sample for the normal loads of your testing progam however. That consolidation step must occur in the DDS machine, so you may have to apply incremental loads to get your test condition.

f-d

ípapß gordo ainÆt no madre flaca!

You are right Fattdad , the core sampling of soil extracted the shale that suffered from shearing
Those samples where completely crushed and highly saturated maybe at or above liquid limit , so it makes sense . Also Terzaghi book and others emphasize on the matter we discussing
Thanks again

Horizontal drains are not effective in fine-grained soils. Are there any sandy beds to target with h-drains?

Long-term question is where is the water coming from? Photo suggests that historical seepage may be stopped up gradient of the road fill. Is there a culvert or DI upgradient that is not working, resulting in wetting of the clays? If so, a subdrain excavated upslope and parallel to the roadway, that will get water directed to below the slide area may be the key.

Well the corkster you are right , horizontal drains are not in my mind.
Idk if there are any nearby water holding structures that are maybe damaged but i dont believe they exist , remember its a mountain range .
Else , there is a nearby tap
My idea since large economical budge cannot be afforded here ,is french drain and maybe remove some soil on the road just to decrease the total vertical stress.3