Rosa T. Affleck

Rapid stabilization of thawing soils: field experience and application

Abstract Thawing soils can severely restrict vehicle travel on unpaved surfaces. However, a variety of materials and construction techniques can be used to stabilize thawing soils to reduce immobilization problems. The US Engineer Research and Development Centers Army Cold Regions Research and Engineering Laboratory (CRREL) and the Wisconsin National Guard evaluated several stabilization techniques in a field demonstration project during spring thaw at Fort McCoy, Wisconsin, in 1995. Additional tests on chemical stabilizing techniques were conducted at CRRELs Frost Effects Research Facility. The results of these test programs were reduced to a decision matrix for stabilizing thawing ground, and used during the deployment of US troops in Bosnia during January and February of 1996. The soil frost and moisture conditions expected during this time frame were predicted using MIDFROCAL (MIDwest FROst CALculator). This paper is an overview of the stabilization techniques evaluated and their recommended application based on the expected soil frost conditions and traffic requirements. Although the experiments were performed with military vehicles in mind, the techniques are suitable for many civilian applications such as forestry, construction, mining, and oil exploration.

CAP PLASTICITY MODEL FOR THAWING SOIL

A material model for soft, wet soil was generated to simulate the deformation behavior of thawing soil under vehicle loading on pave d and unpaved roads. The soil modeled, a frost-susceptible fine sand called Lebanon Sand, was subjected to a full suite of saturated and unsaturated triaxial testing duplicating conditions experienced during large-scale freeze–thaw testing. Material parameters were generated for a capped Drucker–Prager plasticity model with hardening. These were calibrated in triaxial test simulations using the commercial finite element code ABAQUS. The material model was then implemented in several three-dimensional finite element simulations for validation and robustness. THE PROBLEM OF SPRING THAW Spring thaw is a critical time of year for the deteri oration of roads and airfields. Deformation of the road surface (either paved or unpaved) during spring thaw is nearly always the result of defo rmation of the thawing layer, which is weakened though a reduction in density and an increase in moisture as a result of the freezing process. The deformation of the loose, weak, thawing layer is largely plastic, consisting of both compaction and shear. Because of the difficult and time -consuming nature of constructing full -scale test sections and field experiments on thawing ground, we aimed to create a finite element modeling capability, validated with experimental data, which would then be useful for performing computer experiments on a wide range of off-road, pavement, and

Using ground-penetrating radar to delineate regions of massive ice at McMurdo Station, Antarctica

In November through December 2015, ground-penetrating-radar (GPR) data were collected at McMurdo Station, Antarctica, to better understand the near-surface geology, to find and delineate regions of excess or massive ice, and to inform future construction efforts. Of the 55 km of data collected, approximately 40% were analyzed and described in previous studies. In this study, we processed and analyzed the remaining data located within proposed areas for future construction. Both 400 and 200 MHz antennas were used for data collection, with depth penetrations reaching 5 and 10 m for each antenna, respectively. Near-surface features detected include massive or excess ice, bedrock, and buried utilities. Ground-truth data, including soil pits and borehole logs, corroborate our interpretations. A considerable amount of near-surface excess ice likely has anthropogenic origins from runoff refreezing in shaded areas. Our results show that the subsurface of McMurdo is characterized by a substantial amount of frozen ground that will require navigation in both the planning and construction efforts associated with rebuilding McMurdo Station. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR. ERDC/CRREL TR-18-4 iii

Characterizing the Strength Layering of Freezing Ground

A test section was constructed for vehicle testing on frozen soils having overall dimensions of 6 m (20 ft) wide by 32 m (105 ft) long. The section had three test cells. Each test cell was approximately 7.6 m (35 ft) long by 6 m (20 ft) wide, and contained one of three different soils: clay (CL), silt (ML) and silty sand (SM). The test soils were constructed and compacted in four 0.15-m (6-in.) lifts to a total depth of 0.6 m (24 in.). Each lift was compacted with a roller to a target density of approximately 90 to 95 percent of optimum compaction (CE12) to simulate a trafficked un-surfaced road or trail. Various soil characterization tests were conducted during trafficking for monitoring the condition and homogeneity within each test soil. To characterize the test section, frost depth, soil strength, soil density, and soil moisture were measured and examined with several instruments or monitoring tools that worked well on frozen soils. This paper focuses on frost depth and soil strength measurements using various tools and relates the California Bearing Ratio (CBR) to the soil modulus (E or Mr) value using several existing correlations developed for various soil conditions.