Abstract
Hydraulic compactor is an efficient reinforcement machine for loess subgrade. However, it is difficult to control the layered compaction quality of the subgrade. This research presents a real-time layered compactness monitoring method for hydraulic compactor reinforcement of subgrade in loess areas. The hydraulic force coefficient is first introduced, and the dynamic response model of the hydraulic rammer and soil is established. The relationship between the acceleration of the hydraulic rammer and the compactness of subgrade is then obtained based on the collision theory in elastic half space. A full-scale test using a hydraulic compactor to reinforce loess subgrade was also carried out. Results show that the hydraulic compactor obtains the effective influence depth for the reinforcement of loess subgrade. Within the effective reinforcement depth, the relationship between the peak acceleration of the rammer and the layered compactness of subgrade can be well fitted by a quadratic function model. The layered compactness of the subgrade and the working state of the hydraulic compactor can then be remotely monitored at a mobile terminal in real time. Furthermore, the monitoring technology was applied to Huangling-Yan’an Expressway in China, significantly improving the accuracy and efficiency of real-time monitoring of the layered compactness of subgrade in the loess area.
Highlights
Loess is widely distributed in the northwest of China, covering approximately 6.6% of the land in China [1,2]
To obtain the acceleration time history curve of the rammer and read the peak acceleration of each impact, a piezoelectric accelerometer DH131E was installed on the center of the top of the rammer
With the increase of subgrade depth, the subgrade compactness decreases gradually, and the impact of dropping numbers on the degree of compaction slowly weakens. This result is due to the vertical damping in the soil, which leads to an attenuation of the transmission of the tamping energy of hydraulic rammer with depth, and the energy absorbed by the soil decreases gradually
Summary
Loess is widely distributed in the northwest of China, covering approximately 6.6% of the land in China [1,2]. Researchers have established a discrete element model of the hydraulic compactor reinforcing soil through numerical simulation, but this work only focuses on the rammer or the dynamic response of soil individually, rarely combining the two [18]. The experimental research methods of vibratory roller compactor-soil model and some experimental methods adopted in the development of compaction meter provide guidance for this work [19,20,21] The aim of this investigation is to combine dynamic sensing technology with the traditional compaction measurement method. According to the theory of collision, the accelerate the fall of the rammer during the22reinforcement of loess subgrade under the combined whole canand be regarded an incomplete elastic collision, which can be expressed as: rammer action process of gravity hydraulicasacceleration system, and contains initial velocity when the falls.
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