Large-scale pullout device
This device is used to measure the pullout resistance of the soil-geosynthetic composite as well as the stiffness at small displacements. It complies with ASTM D6706 “Standard Test Method for Measuring Geosynthetic Pullout Resistance in Soil” (ASTM 2001) and has internal dimensions of 1.5 m (L) x 0.6 m (W) x 0.3 m (H). The box includes a 50-mm opening at the front and two sleeves 150 mm in length to minimize the influence of the frontal box wall on pullout test results. Using the newly constructed reaction frame and loading facility, the normal pressure applied to the top of the specimen can be varied from 7 to 100 kPa (1 to 15 psi). The hydraulic system can run tests at displacement rates as low as 0.5 mm/min and as high as 10 mm/min.
Large-scale soil-geosynthetic interaction device
This equipment is used for large-scale assessments of the interaction between adjacent soil reinforcement layers under various levels of confining stress. The box includes transparent side walls and measures 1.5 m (L) x 0.75 m (W) x 1.2 m (D). The device includes an adjustable pneumatic normal pressure system, reinforcement clamping and a pullout system. The geosynthetics and soil particles are instrumented with linear potentiometers.
Large-scale direct shear device
This device is particularly suitable for characterization of the shear properties of aggregates and the interface shear strength between aggregates and a variety of other materials. The test bed dimensions are 510 mm (W) x 510 mm (L) x 400 mm (D). Up to 120 kN of shearing force can be applied under overburden pressures ranging from 0 to 350 kPa.
Large-scale triaxial testing equipment for fiber-reinforced soil
This device is currently used to evaluate the contribution to the soil shear strength of fiber reinforcements. With this triaxial device, extension, compression and tension can be applied to a soil sample at up to 150 psi of cell pressure and 10,000 pounds of axial load. It can accommodate a large-scale specimen size, with a diameter of 6 inches and height of 12 inches.
Small pullout device
The Small Soil-Geosynthetic Interaction (SGI) test is used to evaluate the soil-geosynthetic interaction under small displacements. The test facilitates determination of the following parameters, based on the SGI model: yield shear at the soil-geosynthetic interface (τy); confined stiffness of the geosynthetic specimen (JC); stiffness of the soil-geosynthetic composite (KSGC); and unconfined stiffness (Ju) of the geosynthetic, obtained through image analysis.
The test involves sandwiching a portion of a geosynthetic specimen between two layers of soil inside the box and attaching the free end of the specimen to a clamp used to pull the specimen out. The displacement of the confined portion is recorded using LPs and deformation of the unconfined portion is recorded by a digital camera.
The soil volume required for this test is only 4% of that required by ASTM D6706, resulting in improved testing, in terms of repeatability and ease of use, as well as a more expeditious and economical testing procedure for TxDOT.
Centrifuge permeameter for unsaturated soils
The centrifuge includes two permeameter environments, each of which is outfitted with sensors to measure moisture content and suction. Water is passed from the stationary environment to the spinning environment through a hydraulic union. This device is capable of simultaneously testing large duplicate specimens. It includes a unique data acquisition system that can operate under accelerations as high as 600 g’s, facilitating in-flight monitoring of flow processes.
Transparent soil-geogrid interaction device
The transparent Soil-Geogrid Interaction (SGI) device was developed to investigate soil-geogrid interaction. This device facilitates the study of the load-displacement response and deformation of a geogrid under an applied load. Similar to the standard SGI device, a tensile load is applied to a geogrid that has an unconfined end as well as a portion embedded in a soil matrix. Fused quartz saturated with mineral oil is used as a sand surrogate. The resultant mixture is transparent due to the materials’ matching refractive indices. Consequently, both the side and top of the geogrid can be observed while the load is applied. Particle movement can also be tracked via laser illumination.
Transparent large-scale rigid box for transparent soil testing
A large, transparent rectangular box (32 ft³) was developed for the study of large-scale geotechnical problems using transparent soil. A vertical load (static and cyclic) is applied to the box by one of the device’s electro-mechanical actuators. Fused quartz and mineral oil with matching refractive indices can be combined to produce a transparent sand surrogate. Alternatively, Laponite RD can be used to manufacture a clay surrogate. Windows comprise all four sides as well as the bottom of the box, allowing for direct observation of the problem being modeled. Particle movement can also be observed during testing using laser illumination.
Testing environment in MMLS
The Accelerated Pavement Testing (APT) facility at UT Austin houses two indoor experimental pavement test beds under controlled environmental conditions. This setup facilitates simultaneous construction and testing, reducing the down-time associated with pavement test bed construction and demolition. The controlled environment and strict testing protocols offer repeatability of test results and reliability in the data obtained.
The test beds are modular in nature, with multiple 6” collars that can be stacked to construct deeper or shallower sections. Currently, the facility can test any pavement configuration with a total depth of 6” to 36” and width ranging from 36” to 72.” Considering their scalability, the test beds meet the minimum requirements of the test-track according to AASHTO R-50 (2009). Consequently, this facility can be used to determine the relative performance (TBR, BCR, LCR, etc.) of flexible pavements with different configurations.
Large-scale plate load testing system
The latest addition to UT Austin’s Accelerated Pavement Testing (APT) facility is the full-scale APT setup. This facility can test a field-scale (1:1) pavement test section at up to 1.25 times the standard wheel load (40 kN). It consists of one modular test bed measuring 2 m x 2 m x 1.5 m, which complies with AASHTO R-50 (2009). The equipment includes a servo-electric motor-actuator assembly that can apply loads up to 50 kN in a pulse as short as 0.1 seconds (10 Hz). The pulsing can be in the form of a haversine or triangular load. This system is also capable of monotonic load-controlled and displacement-controlled testing.
The main operational characteristics of the large-scale Plate Load Testing (PLT) system include: a 12-inch plate diameter; plate contact pressure of 0 to 100 psi; 112.5-square-inch tire contact area (nominal); pulse time (0-Max-0) of 0.1 to 10 seconds; wheel load of 0 to 11,258.25 pounds; rate of load application of up to 3,600 per hour; and monotonic loading of 1.75 inches per minute to 250 inches per minute.
Large-scale soil-structure interaction device
This device is used to simulate the cyclic soil-structure interaction occurring in jointless bridge abutments due to temperature changes. The box measures 1.5 m (L) x 0.75 m (W) x 1.2 m (D) and includes a transparent side wall to facilitate digital image analysis of motion within the backfill. After placement of the backfill inside the box, instrumented artificial gravel particles are distributed within it. The device can carry out cyclic rotational wall movements (at the top of the wall) up to 7.5 cm in the passive and active directions.
Geocell extraction device
This equipment is used to determine the extraction capacity of geocells filled with concrete and soil-cement mixtures. It is capable of full-scale simulations of the extraction effect that occurs in transportation, hydraulic and geotechnical works using geocells with rigid infills under controlled conditions. In principle, it could be used for different types of loading-displacement applications, either as is or with modifications.
This device applies a vertical load via a two-way hydraulic actuator. The load is measured by a load sensor and can be roughly derived by pressure readings from the hydraulic system manometer. In addition to load, the displacement of the extracted plug is measured by two LPT sensors. Data is recorded with a customized DAQ and LabView module that allows for real time visualization.
The actuator of this device is rated for 20,750 lbs. (92.3 kN) of maximum force; the piston has a maximum pressure of 2,500 psi (17.2 MPa); the hydraulic pump powering the piston has a maximum pressure of 3,000 psi (20.7 MPa); and the LPT sensors have a range of ± 3.0 in (76 mm).
