# Roller-Integrated Acoustic Wave Detection Technique for Rockfill Materials
## 5 Conclusions  
In this study, a new roller-integrated acoustic wave detection technique was proposed; the SCV was utilized as a compaction index for the evaluation of the compaction quality, and an infinite baffle piston radiation acoustic field model (i.e., A-model) was established to accurately estimate the dry density of the NGM. The new technique was adopted to detect the compactness and evaluate the compaction quality in the entire construction area of the upstream cofferdam of a reservoir project in Luoyang, China. The new technique was beneficial to improve the compaction quality and avoid quality defects.  
The following conclusions were drawn.  
1. The SCV value increased with the increase of the number of compaction times. Furthermore, the SCV increased with the increase of the compactness or dry density and vice versa. Moreover, the SCV had a strong linear correlation with the number of compaction times (\(R^{2}\) ranged from 0.7803 to 0.9696) as well as the compactness (\(R^{2}\) ranged from 0.7371 to 0.8064). The comparison analysis of the actual and calculated dry density based on A-model showed that the relative errors were between 0.04% and 5.80%, and the average relative errors were less than 5%.
2. A-model, namely, a relational model between the SCV and the dry density of the NGM, was established. During the modeling process, an innovative differential pulse excitation method was proposed and used to solve the numerical solution of the vertical displacement of the soil surface under harmonic loads. The A-model has been experimentally verified to have high accuracy and can meet the requirements of practical projects.
3. Statistical averaging of in situ measurements in each test strip of the field tests mitigated measurement variations and revealed the high accuracy of the calculated values based on  
Figure 19: Compaction nephogram of Strip 1 using SCV.  
the A-model. This data processing method conforms to the design specifications of rockfill dams and the calculation results based on the A-model are reliable.
4. Compared with existing contact techniques and methods and CMV-based RICM techniques, the new technique proposed in this paper demonstrated several advantages, such as higher accuracy, smaller discreteness, convenience, and suitability for detecting the compactness of rockfill materials with particle sizes larger than 200 mm. In addition, based on the CAWDS developed in this study and the RTK-GPS technique, the SCV could automatically be acquired and used to characterize the compaction status of the NGM as a nephogram. Based on the nephogram, the compaction performance in the entire work areas could be clearly determined and support could be provided for quality control in a timely manner. The above results showed that the SCV could serve as a real-time monitoring index characterizing the compaction quality of rockfill dam materials.  
This work was supported by the National Basic Research Program of China (973 Program, Grant No. 2013 CB035902) and the National Natural Science Foundation of China (No. 51339003). The costs to publish in open access have been covered by the funding.  
[PERSON], [PERSON], and [PERSON] proposed a roller-integrated acoustic wave detection technique for rockfill materials. [PERSON], [PERSON], and [PERSON] conceived and designed the experiments. [PERSON] performed the experiments, analyzed the data, and wrote the initial draft of the manuscript. [PERSON] and [PERSON] reviewed and contributed to the final manuscript.  
The authors declare no conflict of interest.