Geotechnical Laminar Box

Geotechnical Laminar Box.

Geotechnical Laminar Box

The Geotechnical Laminar Box is designed for soil-foundation-structure interaction studies at or near full scale. The laminar box and the soil contained within deform in a manner that simulates free ground response under simulated seismic excitations. The laminar box can be assembled to a maximum height of six meters.

Technical Specifications

General Dimensions and Information

  • The nominal internal dimensions are: 5 meters long x 2.7 meters wide.
  • The enclosed volume can be filled with saturated sand or soil to a maximum capacity of 82.5 cubic meters, using a hydraulic slurry pump and distribution system.
  • A supply of Ottawa (F-55) sand is stored in three 50 cubic yard outdoor storage containers and may be available for use.

Laminate Information

The structure consists of 39 rings or laminates (I-beam-cross sections) stacked vertically to form a rectangular box. Two base rings are available:

  • A level ring for assembling and testing a vertical soil column
  • A sloped ring that allows the testing of a soil column with a 2-degree incline

Each laminate is supported by ball bearings that are mounted within the depth of the laminate below. The laminates are separated by a 5 mm gap, allowing them to freely displace relative to each other. The stacked laminates are mounted on a sliding steel base assembly that is supported by 288 ball bearings. The sliding base is installed on a steel plate that is tied to the strong floor. Two 110-kip dynamic actuators are connected between reaction blocks and the sliding base. These actuators impose seismic motion on the sliding base. An internal liner (membrane) consisting of two layers of Firestone EPDM (inner 45-mil, outer 60-mil) provide for the containment of the test sand or soil. The laminar box assembly is surrounded by a safety restraint system consisting of steel beams and columns with adjustable spring-loaded over-travel bumpers. The bumpers along the sides of the box are designed to prevent transverse motion of the laminates during testing. The bumpers on the east end of the box (opposite the actuators) can be positioned to limit displacement of the laminates, which is critical for tests with a sloping ground configuration.

Sensors and Other Equipment

An instrumentation frame oriented longitudinally along the top of the laminar box provides a stable reference frame for the deployment of multiple sensors. Available sensors include:

  • Submersible accelerometers
  • String potentiometers
  • Piezoelectric pore-pressure transducers
  • A MEMS shape-array cable system measuring acceleration, velocity, and displacement at 300mm intervals
  • ASTM stnadard cone penetration system (CPT)
  • CPT that can be attached to the overhead frame in several locations along t he length of the box

Other laboratory hardware and equipment can be used to support laminar box research, including 300+ channels of data acquisition, signal conditioning and synchronization hardware and software; a 40-ton overhead gantry crane; heavy material moving and lifting equipment, three personnel lifts, and digital cameras with multiple resolutions.

Important Information Regarding Use and Scheduling

The membrane installed in the Geotechnical Laminar Box is an expendable component of the system and is not provided by the SEESL site. Any researcher or industry client proposing to conduct work using this equipment must budget funds to procure an acceptably robust new membrane for their project.
 
In the event a proposal uses soil or sand other than the Ottawa F-55 sand that is currently available here at SEESL, the procurement, transport and storage costs for up to 100 cubic meters of media must be budgeted. The costs for project-specific instrumentation must also be budgeted.