Sampling:

We conduct geotechnical investigations to obtain information about the physical properties of soil and rock around a site to design a solid and sound foundation that will properly support proposed structure.

Geotechnical investigation includes surface exploration and subsurface exploration of your site. Surface exploration includes geologic mapping, geophysical methods, and photogrammetry, or our geotechnical professional walking around on the site to observe the physical conditions at the site.

The site subsurface conditions are explored with soil sample sets taken inside the proposed footprint. Boring depths are approximately 20 feet below ground surface. The borings are advanced using a GeoProbe direct push/hydraulic hammer system. Sample collection and field tests are performed in general accordance with ASTM procedures or other accepted methods.

Undisturbed samples of cohesive soils are obtained using a Macro Core sampling tube. The Macro Core sampling tube extrudes the sample into a clear PVC liner. The Liner is 1.5” in diameter and 48” in length. Five (5) samples of approximately 48” in length are collected for each bore hole. The samples are identified on the liner according to boring number and depth. Hand Penotrometer and Dynamic Penotrometer tests are conducted in the field. Hand Penotrometer readings are collected and recorded on the soil that remains in the cutting shoe after each sample is retrieved. Dynamic Cone Penotrometer tests are performed at the depth of the bore hole following the removal of each sample. A small portion of each sample is collected in a container and weighed for determination of natural moisture content. After field testing and logging the sample, it is sealed for transport to the lab.

Selected soil samples are tested in the laboratory to determine material properties for our evaluation. These tests include: Moisture content, percent passing the #200 sieve, Atterberg limits, Hydrometer particle size analysis, and unconfined compressive strength.The laboratory testing is performed in general accordance with the ASTM procedures.

Filled soil collection tubes ready for analysis.

Analysis:

Dynamic Engineering uses the computer software VolFlo to evaluate the soil strata using the principles of unsaturated soil mechanics. VolFlo is a two dimensional moisture flow analysis program that is used to determine the Post Tension Institute design values of edge moisture variation (em) and the maximum unrestrained differential soil movement (Ym).These design values are given for both Edge Lift conditions and Center Lift conditions. Edge Lift occurs when the presence of abundant moisture at the edge of a foundation causes the soil at the edge to expand and therefore lift the outer perimeter of the foundation. Center lift occurs when the moisture at the edge of a foundation is desiccated and the outside perimeter of the foundation drops (equivalent to the center lifting) with the shrinking soil.

• The transition from extreme dry conditions to extreme wet conditions could cause a differential movement of the soil approximately equal to the Ym edge lift variable .This differential movement will occur within approximately the Em edge lift value of the edge of the slab. This is representative of an edge lift or swell condition.
  
• The transition from extreme wet conditions to extreme dry conditions could cause a differential movement of the soil approximately equal to the Ym center lift value. This differential movement will occur within approximately the Em center lift value of the edge of the slab. This is representative of a center lift or shrinkage condition.
  
• The information determined by the VolFlo analysis is plugged directly into the Post Tensioned Design Institutes foundation design equations to determine beam spacing and depth, allowable bearing, and steel installation. A pier analysis, if required, and deflection analysis are also conducted as part of the foundation design process.