NEES @ UC San Diego

Laminar Soil Shear Box

Laminar Soil Shear BoxFull Size

A full-scale laminar soil shear box was designed and fabricated for full-scale testing of soil-structure interaction under static or dynamic test loading conditions. This soil box, funded by the California Department of Transportation (Caltrans), has a length of 6.7 m (22 ft), a width of 3 m (9.6 ft) and a height of 4.7 m (15.2 ft). The laminar soil box consists of 31 steel laminar frames, each separated by a steel roller system on stainless steel lined webs, to allow for uni-directional movement. Movement of the laminar frames, when subject to uni-directional dynamic loading, provides a mechanism by which energy propagating through the soil can be absorbed. This energy absorption simulates in-situ soil conditions, in which energy can propagate through a uniform soil deposit over great distances with minimal energy reflection.

The laminar frames consist of: nine frames of W8x35 steel section in the lower region of the box, sixteen frames of W8x15 steel section in the mid height region and six frames of W8x10 steel section in the uppermost region. This variation in steel frame section sizes minimizes weight, so that the ratio of laminar frame weight to soil is in the range of 8 to 10%; a range common in similar full-scale laminar soil boxes in Japan. Displacement of the frames in the direction perpendicular to motion (or shaking) due to high soil pressures and potential hydrodynamic forces (if water is present) will be restrained by a steel tower reaction system. The tower system was designed to have a natural frequency 2.5 times the soil box natural frequency.

This soil box will allow full-scale testing of reinforced concrete piles, such as a cast-in- drilled-hole (CIDH) pile, with a diameter up to 0.60 m (2 ft). The effects of liquefaction (loss of soil strength in a saturated soil deposit) can be studied as well, with the aide of a watering system in the steel framed base. Water and soil will be kept inside the laminar soil box with a waterproof polypropylene liner. When filled with a soil of unit weight 1922 kg/m3 (120 pcf), the container will hold approximately 172,000 kg (380,000 lb) of soil.

Laminar Weight to Soil Weight Ratio (target) 8 — 15%
Length to Height Ratio L/H < 2.0
Width to Height Ratio W/H < 1.0
Deflection Due to Soil-Water (2000 kg/m3) L/1000
Ratio of Frequency of Lateral Support (flat) to Interested Maximum Frequency (fmax) flat/fmax > 2.5
Ratio of Out-of-Plan Acceleration to Maximum Horizontal Acceleration 0.1 — 0.25
Ratio of Maximum Vertical Acceleration to Maximum Horizontal Acceleration 0.5 — 0.67
Laminar Frame to Soil Weight Ratio < 0.1
Lateral Support to Soil Weight Ratio < 0.1