Soil Test/ investigation|How to soil test to make building

Soil Test/ Investigation|How to soil test to make Building. 

Soil test lab-digitalsoilsurvey.blogspot.com

Having a geotechnical engineer/technician (engineer) present during drilling investigations is highly recommended as they specialize in field reconnaissance, coordinating and directing the drillers, logging boreholes, and collecting soil samples. Having an engineer onsite during drilling investigations will cost more initially, but if subsurface information is inaccurate or inadequate, a greater number of assumptions need to be incorporated into the design, which increases the potential for negative impacts later in the design life and/or costly surprises during construction.

If an engineer cannot be onsite during drilling investigations, good communication with the drillers prior to performing soil borings will help ensure the most valuable information is obtained. It is important the drillers understand the purpose of the investigation. Explain that drilling is being done to find soils indicative of restrictive layers; i.e. soils that inhibit the flow of water. Listed by most restrictive to least restrictive, these soils are: clay, silt, sand, and gravel. Provide drillers with the following guidance:

If recovery in a split-spoon sample is less than six inches, drill two feet deeper and perform another split-spoon sample.
If a confining layer is found, or there is low recovery in a split-spoon, reduce sampling intervals to every two feet. Record the presence of the most restrictive layer, even if that material is not the most abundant in the split-spoon sample.
If low recovery is encountered, explain in the field notes why the driller thinks this is happening (i.e. gravel in the shoe of the split-spoon)
Blow counts or “N” values found during a Standard Penetration Test (SPT) are critical to determining the presence of restrictive layers. For information on standard penetration tests, see here
If soil boring auger refusal is encountered prior to depth desired, offset approximately five feet from initial borehole, blind -drill (continuous drilling without soil sampling) to refusal depth, and continue drilling/sampling from that point. Note there will be an additional cost associate with the offset and blind drill. If the second attempt results in the same refusal as the first, the driller should call the engineer to inquire about next steps immediately, prior to leaving the site. During that call, ask drillers to describe why they think refusal has been met and, if necessary to drill deeper, discuss alternative drilling methods or an additional offset.
Ask the driller to include soil type, recovery, blow counts, and presence of water in their field logs, and request a copy of their field logs.
It is highly recommended that the drillers use a standard form (attached). If they do not use a standard form, request to see their form prior to drilling and suggest modifications as necessary.
To the extent possible, the final boring logs should contain information listed in the table Summary of Information to Include on a Boring Log (see below).
Information gathered from soil samples
Soil samples help provide a general subsurface profile and can be used to measure engineering properties, including those properties indicating the presence of a restrictive soil layer. When a soil boring is performed to determine if a site is suitable for infiltration, the following information should be requested from a soil boring company