Abstract

Lightweight cellular concrete (LCC) is an aerated or foamed concrete where 25-80% of the concrete matrix consists of air voids. The high volume of air voids reduces the strength but significantly decreases the weight of the material, which has made it an attractive alternative to soil for retaining structure backfills. Though the use of LCC has increased, little research has been performed on the large-scale behavior of retaining structures containing LCC as backfill. This research test attempts to fill knowledge gaps found with regard to the use of LCC in a mechanically stabilized earth (MSE) wall with a trapezoidal or sliver fill by examining the nature of LCC strength criteria from large-scale failure, failure mechanisms, and failure criteria. A large-scale test box (10 ft. wide x 12 ft. long x 10 ft. high), surrounded by a steel resisting frame, was constructed and filled with a silty sand backfill soil in a 1:1 stair-stepped slope and an LCC sliver fill. The west-facing wall was a two-paneled MSE wall with 16 ribbed steel strip reinforcements running through the LCC backfill. The LCC was poured over three days in equal height lifts to ensure stability. A total of 64 sample cylinder molds and four split mold shear boxes were filled with LCC during placement to help identify LCC material properties, which included density, unconfined compressive strength (UCS), and shear strength. A surcharge test was performed on the large-scale test box six days after initial placement of the LCC due to the unanticipated high strength gain and density found within the placed LCC. Instrumentation collected data on displacement, shear plane, lateral wall pressure, and reinforcement strain throughout testing. Initially, four hydraulic jacks were used during surcharge testing to induce a uniform surcharge load to fail the sliver-fill MSE wall. The strength limit of the steel resisting frame was reached before failure, at which point the number of hydraulic jacks was switched to three for a more critical loading condition. The test was again terminated before complete failure when the steel resisting frame strength limit was met. Though failure was not completed, the sliver-fill MSE wall failure had initiated before testing was terminated at a surcharge load of 70 psi. Results identify the initiation of shear failure within the LCC at about 65 psi, with maximum lateral and axial displacements of about 0.5 in. and 1.2 in., respectively. The shear failure occurs at about 52% of the average UCS of 123 psi. An arcuate shear plane, contrary to the traditional bilinear MSE wall failure surface with inextensible reinforcements, was identified within the LCC backfill, which initiated from the toe of the MSE wall and ended about 8 ft. back from the top of the MSE wall, using lateral displacements from Sondex tube profilometers in the backfill.

Degree

MS

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2023-04-06

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd12711

Keywords

MSE, sliver fill, LCC, large-scale test

Language

english

Download

Included in

Engineering Commons

Share

COinS