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I realize the beta=tan(phi)*tan(delta) but decided not to use it to avoid correlate the SPT and phi values. The following formulations: beta=1.2-0.2SQRT(Z) beta=1.5-0.244SQRT(Z) are given in GEC 8 and am comparing with the CFEM beta values. I am trying to understand the differences. Seems...

Hi - I am analyzing boreholes with 200-250 ft depths in predominantly silt, clayey silt or sandy silt. No Shelby but only SPT. Correlations are often through N-values, which I assume is the raw SPT obtained in the field. For example Beta= (N//15)* (1.2 - 0.11 sqrt(Z). or Phi= 0.3N + 27 or...

geotechguy1- what is CFA manual? I could not readily find it. Thanks.

Thank you geotechguy1 for providing references on beta. The term I used like sandy clayey silt was meant to be either a clayey silt or sandy silt. My apology if sounded like a classification name. The point was if there are references for beta values that are not for purely silt or purely clay...

I am employing the beta method to calculate the ultimate load capacity of relatively long piles (35-40m). The soils encountered are predominantly clayey sandy silts, as well as sand. The Standard Penetration Tests (SPTs) conducted in the field often exceed 30 or are reported as refusal before...

Thanks EireChch to point out the friction angle vs coefficient of uniformity, I could not readily find BS8004 but saw the attached figure and wonder how widely it is used in practice without consideration of the soil compactness...

I understand the difficulties to answer a general question of this nature but thanks all and in particular geotechguy1 for your useful hints. While the moisture content is a useful data for fine grained soils, I am still interested to know how to utilize the moisture content test results in...

Hi, I have three 250ft boreholes with only SPTs every 5ft for a heavy foundation of 1000 m2. The soils are predominantly silt, some clayey silt and (silty) sand in a till context. The silts to me err on the sand type rather than clay. I will have some Atterberg limit tests to verify. Grain...

Albert Atterberg invented the test apparatus for liquid limit with a porcelain bowl in 1900 that was then upgraded to a metal bowl in 1932. These two great engineers still remain pioneers. The attached picture may indicate the state of the art of industry during Atterberg-Casagrande marvelous...

Thank you. I do not recall having recent dialogues with structural engineers to know how they use the allowable bearing pressures given by a geotechnical engineer. It seems they multiply the allowable bearing pressure by the FoS used by the geotechnical engineer and then apply the LRFD method...

Hi I understand well the concept and application of FoS. However, having gone through the Canadian Foundation Manual, I have a difficulty to understand the geotechnical resistance factor. For example, a resistance factor of 0.5 is recommended for vertical bearing resistance of shallow...

Thank you for the helpful comments.

Thanks, geotechguy1. That was relieving [dazed] and conveyed the message well. My gut feeling is that clays are sheet or needle minerals with surface chemistry rather than an assumed equivalent spherical grain in hydrometer's Stoke law measurements. As such Atterberg limit test might better...

The fine soil materials classifications are unusually made based on A-line in Casagrande Chart. I have seen some engineers classify the fine soil based on the result of hydrometer test only and call it silty clay if the percentage of clay from hydrometer test is more than silt or clayey silt if...

Proceeding to the next stage, if the pile lengths (D) in the group are not all of the same lengths, how do they establish the equivalent raft at 2/3 D for settlement calculations. Would the D be: - the average length of all piles, - the length of perimeter piles or - the longest pile? Thank...

attachmenthttps://files.engineering.com/getfile.aspx?folder=c2443826-5776-4c89-aac0-bdc7c19efbf4&file=IMG_4172.jpeg

Thanks. I know realize that Look’s suggestion maybe come from the equivalent raft idea and that the 1.5B is the influencing zone below the raft as in the attached figure (if upload). The influencing bulb with a depth of 1.5B is understandable when we have end bearing poles and for settlement...

Thank you for all the valuable feedback. I assume if the building is 25m wide, for a prospective 40m pile at least one borehole should extend to 65m. I assume Burt Look has had the pile group effect in mind.

Thanks DaveAtkins. The bedrock is expected to be approx. 300 ft deep overlain by clayey sandy silt materials with some sand interlayers. Just wondering what would an overall exploration depth be even if we get some high N values at a depth of 80-90 ft.

I am working on ground investigation for a 28 floor high building on predominantly dense clayey sandy silt soils. I would like to know how deep others have gone down for boreholes. If it was a dam site, one would expect a borehole depth equal to the dam height. I do not think there would be a...