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I am working on a project in an old alluvial flood plain with liquefiable sands 40-50' deep on top of sandstone. The soils engineer has recommended helix anchors, embedded 5 feet into dense sandstone. I don't have much experience with helix anchors this deep, but have heard that the longer they...

Hi All, I have noticed as of late that soils reports include less and less lab testing. It seems that people take some blow counts, measure the moisture and call it a day based on some loose correlations with phi values, cohesion and bearing capacity. When do you think lab values are absolutely...

In this particular case, there are no slope stability issues, just about 8 feet of sand with fairly low blow counts that can be considered below the ground water table. LiquefyPro was used to calculate the settlement, but a safety factor (factored into the CSS value)of only 1.1 was used, whereas...

Hi All, I am taking a poll to see what people are using for a factor of safety against liquefaction in California. We are in the Central Coast region, and it seems that many soils engineers use a factor of safety of about 1.1 to 1.3 for single family dwellings. The local jurisdiction requires a...

Hi All, I am working on a project where an existing bridge has been built within a mapped floodplain (Zone A). There is no FEMA BFE at this site, but it is clear from other indicators that the bridge is overtopped by up to 10-15 feet during severe storms. The client wants to laterally widen...

Hi all, I have a question regarding the definition of "significant settlement" for foundations in California. Basically, a soils report has defined a liquefiable layer of soil from about 10' below grade to 21' below grade. In a seismic event they anticipate about 1.3" of settlement due to...

Thanks for the input - basically, the site is located in a lowlying area equidistant between a river and a slough (each about 1/2 mile away)and the soil is composed of clay with very low permeability. The soils engineer has performed investigations on several parcels in the immediate vicinity...

I am currently working on a project where the soils engineer has called for conventional foundations in soft, expansive clay soils. (Class CH, Blows 4-9 to 41' in depth). The foundations have been deepened to 5', the level of a fairly stable water table. The soils engineer states that...

Thanks for your input, BigH. As a Civil Engineer who has not specialized in Geotechnical, it is difficult to know when to trust the soils engineer versus asking for more tests (what I learned in school..). Also, there are certain tests that are required by the Unified Building Code for...

Thanks for all the comments. Obviously I cannot divulge which firms are putting this statement in their reports, but there are several in my area. Usually this is accompanied by some borings, blow count data, penetrometer readings and just about no testing other than moisture content - that is...

I often see the following excerpt in soils reports: "Since water has a significant influence on soil, the natural moisture content provides an indicator of the soil's compressibility, strength, and potential expansion characteristics." I never see any references to moisture correlations in the...

I am a civil engineer reviewing the geotechnical investigation for a foundation retrofit of a house in an area with firm to soft clays. (Blow counts of 6-12 in upper 10 feet, drastically dropping to 4-5 down to about 41 feet) Groundwater is at 5' below grade. The only testing done has been...