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BigH - Relative compaction was estimated using dry densities measured from driven ring samples and a compaction test of remolded soil from a bulk sample from the same borehole. I realize that ring samples, especially in a sandy soil, are disturbed and that test results may indicate either...

Relative compaction, as compared to the max dry density performed on a representative sample. Burland and Burbidge does account for the incompressible layer. I'll check out Tomlinson's book regarding Winkler method. Thanks

Let me correct myself. My mats range in size up to about 20' by 40' and the depth of influence is cutoff at about 12 feet (beneath base of mat) by very dense bedrock. The 'old fill' is unsaturated, silty sand with relative compaction about 85% and SPT field blow counts of about 12. The...

I am to provide a coefficient of vertical subgrade reaction for design of a mat slab over an older sandy fill material. Based on the dimensions of the mat slab the depth of influence is about 12 ft. Settlement analyses (Burland and Burbidge) indicate that up to 1 inch of settlement can be...

I often get requests to allow old AC pavements to be grinded and mixed with soil to be placed as a fill. Besided environmental issues, are there any legitimate reasons why this is a bad idea?

I selected the Schmertmann method due to the low fines content of the soil. I do understand that the 1:1 stress distribution is conservative and that a 2v:1h is more realistic, but where is this supported in the literature? Note that column footings are integrated into the continuous perimeter...

Background: Using Schmertmann's method I estimated settlement below a proposed column footing and recommended removals below the footing to reduce maximum settlement to less than one inch. I recommended that removals extend beyond the footing a distance equal to the removal depth. This is...

I am trying to estimate the secondary compression index following removal of a surcharge load. Is there a reasonable way to do this knowing the existing and future states of stress and C-alpha (normally consolidated)?

Is it appropriate to provide lateral earth pressure recommendations for design of a cantilever retaining wall that includes both active and at-rest values? For example, at locations where a wall turns, say 90 degrees, it is essentially restrained against rotation and therefore the strength of...

BigH - undrained strengths of 0.4-0.6 (20-27 ft) and 0.8-1.1 (>27 ft) based on mini torvane at end of shelby tube. Moisture content ranged from about 28-36% (20-27 ft) and 20-25% (>27 ft). No limits yet but suspected to have LI of about 0.5. Even some soft clay samples appeared unsaturated...

Fatdad - I do have good data, however I am attempting to evaluate settlements that may have been caused by dewatering as part of a forensic study - just trying to avoid taking a 1-D consolidation settlement analysis on potentially unsaturated samples (again based on visual observations only) to...

...determine the coefficient of consolidation.... I meant the compression index.

To determine the coefficient of consolidation, that is true. However, Terzhagi's 1-D consolidation theory is built on two basic assumptions: 1) the soil is homogenous, and 2) the sample is saturated. If the sample is not saturated you can not used the effective stress principle, which equates...

Thanks for the input. I also suspect sandy layers somewhere in the profile but do not have any data to support that. Even the log for the adjacent parking garage excavation backcut mentioned no sand. Actually the water readings were easily approximated during drilling (wet rod, sampler) -...

Gents, A site in an alluvial deposit has a water table ranging in depth from about 18 to 24 ft (based on boring logs). The soil from a depth of 10 to 30 ft is a clay, generally consistent in color (munsell), water content (25 - 35%), dry density (85 - 95 pcf) and fines content (75 - 95%)...

Thank you for your responses. I have modeled a preconsolidation profile and secondary settlements (not significant over 50 yr design life) have been evaluated using laboratory consolidation data at several depths. One of my concerns was: if the surcharge is removed prior to the end of...

A site consists of a soft clay deposit about 10 to 30 feet BGS. The ground water elevation is about 8 feet BGS. Dewatering is not an option for environmental reasons and therefore adequate removals can not be performed. An areawide fill 20 feet in height is proposed. Static settlements are...

Storm drain lines located up to 65 feet below existing grades will be supported by consolidated, sedimentary bedrock. Conventional grading methods will be used to install the lines, therefore at locations of manholes, the adjacent soils will consist of granular (SM and SP-SM with gravels)...

Thanks for the response geopave. Peak strengths seem to be just fine. I agree that as the fines content approaches zero, so should the residual cohesion. In theory, every soil will have zero residual cohesion if sheared at a slow enough rate. We are running one cycle on the direct shear...

Local jurisdictions require that safety factor calculations for static slope stability and infinite slope stability be based on residual, drained shear strength parameters obtained using a direct shear machine. I am consistently getting values for cohesion around 100 to 200 psf, and values for...