Evaluation Method for Bearing Capacity of Fine-Grained Soil Subgrade Based on Multiple Moduli

Abstract

The bearing capacity of the existing fine-grained soil subgrade is mainly achieved by measuring the modulus, and its testing methods can be divided into two categories including static method and dynamic method. The data connection between the two is still lacking in systematic research. The traditional BB (Benkelman Beam) static test has disadvantages such as slow detection speed, low accuracy, and poor reliability due to the use of deflection index, which is not fully applicable to the expressway. To this end, dynamic and static comparison tests were carried out and a rapid test method for subgrade bearing capacity based on Soil Stiffness Gauge (SSG) and Portable Falling Weight Deflectometer (PFWD) with dynamic modulus was proposed. To establish the connectivity of the static and dynamic modulus, modulus-dependent prediction model was developed. The results show that the multiplier power model with modulus ($$$$) is superior to the usual linear model (E_BB = 0.9415E_PFWD − 6.1507, R² = 0.9639; E_BB = 0.7878E_SSG − 0.4566,  R² = 0.8894), and it can replace the traditional BB method. PFWD and SSG were found to be reliable devices with faster and more accurate monitoring of the modulus change of the fine-grained soil subgrade. But they have the property of overestimating material modulus, the modulus ranking of the three instruments is obtained. In this way, it provides a reference for the dynamic and accurate determination and scientific evaluation of the bearing capacity of the highway subgrade.