Geotechnical Laminar Box
Geometry
The UB Full-scale prototype 1-g soil and
soil-structure interaction testing facility consists of a 2-D modular laminar
box (Module A1: 2.75x5x6.2m, internal dimensions). The 2-D laminar box is made
of 24 laminates, separated and supported by ball bearings, facilitating 2-D
motions, including ability to simulate sloping ground subjected to large
deformations. The box can simulate boundary stresses closely to that of a free
ground. The laminar box can also be reconfigured into two other configurations
or modules (module B1: two boxes 2.75x2.5x3.1m each or module B2:
2.75x2.5x6.2m) or at a reduced height. The box can allow up to 15% shear strain
in general, larger deformations for selected cases of loadings, and large
permanent deformations on a case-by-case basis, subject to safety and other
limitations. Figures 3 present schematic diagrams of the laminar box
modules. Figure 4 shows a picture of the laminar box.

(a) Module B1: 2.75x 2.5x3.1 m (b) Module B2:
2.75x 2.5x6.2 m (c) Module A1: 2.75x5x6.2m (d) 2-D Bearing
(e) Module A2: 2.75x5x3.2 m (not shown)
Figure 1: 2D Laminar Box Modules at SEESL

Figure 2: Laminar Box (1-g Full scale Tests) on the Strong
Floor

Figure 3: A typical pile test configuration

Figure4: Laminar Box in Test Area 2
Features
Table 1: Laminar Box
Module Dimensions & Details
|
Module
|
A2
|
B1 and B2
|
A1
|
|
Box-Internal Base Size (mxm)
|
2.75x5
|
2.75x2.5
|
2.75x5
|
|
Box-Height (m)
|
3.1
|
6.2 or 3.1
|
6.2
|
|
Box-Metal Weight (empty)
(tons)
|
8.5
|
11.2 or 5.6
|
17.0
|
|
Box-Max Soil Vol. (m3)
|
38.6
|
34.6 or 17.3
|
77.2
|
|
Support
|
Steel-bridge-spanning two tables
|
Steel-bridge-spanning two tables (6.2m) or on a
single table (3.1m)
|
Strong Floor
|
|
Number of Laminates
|
12
|
24 (or 12)
|
24
|
|
Laminate Thickness (m)
|
0.26
|
0.26
|
0.26
|
|
Interlaminate Bearings
|
Ball Units
|
Ball Units
|
Ball Units
|
|
Spanning-Base Steel Bridge
(tons)
|
7.5
|
7.5
|
7.5
|
|
Payload Capacity
|
40g-ton
|
40 g-ton (6.2m) or 20 g-ton (3.1m)
|
0.3g max
|
|
Maximum Weight (incl box
& soil)
|
100 tons
|
100 tons (6.2m) or 50 tons (3.1m)
|
185 tons
|
|
Shaking Dir.
|
Horiz: X, Y
|
Horiz: X, Y
|
Horiz: X or Y
|
|
Inter-laminate displ. (nominal)
limit (mm)
|
36
|
36
|
36
|
|
Inter-laminate displ. (for
special tests) limit (mm) (may increase this limit for 1-D tests)
|
74
|
74
|
74
|
|
Permanent Displacement
between Laminate
|
To be decided on a case-by-case-basis
|
To be decided on a case-by-case-basis
|
To be decided on a case-by-case-basis
|
Table 1 presents the dimensions and details of the
various modules. The load capacity characteristics are to be considered
preliminary, subject to verification and update. In its largest configuration
(Module A1: 2.75x5x6.2m), the laminar box is supported on the strong floor, on
a steel shaking base frame supported on rubber/sliding bearings. It can be
actuated in 1-D using one or more of the UB-NEES 100 ton fast dynamic actuators
(MTS), or in 2-D by using two or more 100 tons fast actuators mounted at 45
degrees on the new UB-NEES reaction wall (30ft high, 41ft wide). The total
weight of the box filled with sand is about 150-170 tons, whereas the maximum
horizontal dynamic actuator capacity is 90 tons in each horizontal direction
simultaneously or 180 tons in any one direction. Thus very large shaking g
levels are possible. The actuators can be fed with any recorded motion and the
controllers can be set to compensate for any compliance effects to accurately
shake the base of the soil to meet any desired recorded earthquake motion. Data
acquisition systems are available to monitor up to 256 channels at high
frequencies. High resolution imaging tools can be positioned to capture
deformation patterns at any selected zone in the soil box.
In its smaller configurations (modules A2, B1 and B2),
the laminar box may be mounted on a shake table with a maximum payload capacity
of 50 tons weight including the box weight. Where higher weights are expected
the box may be assembled over a steel base frame supported by two identical
shake tables allowing up to 100 tons maximum weight, including the weight of
the box and the steel base frame. The shake table payload-acceleration
characteristics are presented elsewhere. Typically each shake table can operate
at up to 1.15g at a nominal payload weight of 20 tons, and the acceleration
decreases with an increase in payload weight. The shake tables have 6 degrees
of freedom, but the 1-g soil tests are limited to 1-D or 2-D at this time.
Sand may placed inside the box by air pluviation, wet
pluviation, or hydraulic filling. Due to dust control considerations the
hydraulic filling method is preferred. A close-loop system has been developed
to pump sand-slurry using sand-slurry pump from sand containers located just
outside the Test Area 2 building. In the case of dry pluviation, soil
saturation may be achieved by percolating by CO2 through the soil
and seeping water with the aid of vacuum suction.
The facility also has capability to simulate the
inertial effects of the building/bridge pier etc. on the foundation/pile cap
via mass-spring system and/or hybrid system where the loads/moments from the
building/bridge pier can be applied via fast actuators mounted on the reaction
wall. The soil experiments also can be coupled with other physical experiments
at UB or elsewhere and/or computational models that simulate the response of
the system or structure supported on the soil.
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