Chenchen Li

Timely and accurate detection of pavement distress is crucial for maintenance decisions. Despite advances in detection methods to ensure accuracy while increasing computational speed, there...

The shear strength of unsaturated granite residual soil (GRS) will decline rapidly when moisture content increases, because of loss of matric suction in the soil. This can lead to slope instability and embankment collapse during rainfall. Determining the matric suction of GRS accurately at different conditions can improve the accuracy of stability analysis. Generally, matric suction can be characterized as the soil–water characteristic curve (SWCC), and it is closely related to soil microstructure. In this study, the entire range of matric suction was measured using a combination of pressure plate method, filter paper method, and vapor equilibrium method. Microstructure change was investigated based on mercury intrusion porosimeter tests, in which the pore size distribution (PSD) curves of GRS samples with different initial densities and moisture content were measured. The PSDs of samples before and after wetting were also measured and compared to investigate the influence of water intrusion. Test results indicate that the combination of measurement methods can cover the entire matric suction range. The microstructure of GRS with different initial conditions presents a clear bimodal PSD. At the same density, the increase in initial moisture content can increase intra-aggregate pores and decrease inter-aggregate pores. When initial density increases, only the volume of inter-aggregate pores decreases. Wetting can decrease inter-aggregate pores and increase intra-aggregate pores. Finally, the Li model is applied in SWCC fitting for tested samples, the result of which performs well with a high correlation coefficient (R² > 0.95) and is recommended for GRS analysis.

This paper proposes the application and manufacturing of piezoelectric devices based on pile and arc-bridge transducers to harvest mechanical energy from concrete pavement. Multi-scale experiments are conducted to clarify the influence of electrical connection, load resistance, traffic speed, and loading times on the electrical properties of the harvesters. The reduced-scale test shows that the transducers should be connected to rectifiers before being connected as an array. Moreover, the output power of the arc-bridge transducer with resistance variations is unstable compared with that of the pile transducer. Accelerated pavement testing illustrates that the output power of the half pile array device increases to 1.7 mW with an optimal resistance of 10.0 MΩ; reducing the internal equivalent resistance is a potential way to increase the energy output. The results also show that the load speeds significantly influence the profile of the voltage and have a minor effect on the generated electric energy in the tested conditions. Furthermore, the electrical properties of the piezoelectric device exhibit no statistical degradation after the electrical fatigue test of 100,000 tire loads, indicating a novel electrical fatigue performance. The findings in this paper can further guide the application of such piezoelectric devices in concrete pavement.

To advance the development of piezoelectric energy harvesters, this study designed and manufactured bridge-unit-based and pile-unit-based piezoelectric devices. An indoor material testing system and accelerated pavement test equipment were used to test the electrical performance, mechanical performance, and electromechanical coupling performance of the devices. The results showed that the elastic modulus of the pile structure device was relatively higher than that of the bridge structure device. However, the elastic modulus of the two devices should be improved to avoid attenuation in the service performance and fatigue life caused by the stiffness difference. Furthermore, the electromechanical conversion coefficients of the two devices were smaller than 10% and insensitive to the load magnitude and load frequency. Moreover, the two devices can harvest 3.4 mW and 2.6 mW under the wheel load simulated by the one-third scale model mobile load simulator, thus meeting the supply requirements of low-power sensors. The elastic modulus, electromechanical conversion coefficients, and electric performance of the pile structure device were more reliable than those of the bridge structure device, indicating a better application prospect in road engineering.

To improve the energy harvesting efficiency of the piezoelectric device, a stack units-based structure was developed and verified. Factors such as stress distribution, load resistance, loads, and loading times influencing the piezoelectric properties were investigated using theoretical analysis and experimental tests. The results show that the unit number has a negative relationship with the generated energy and the stress distribution has no influence on the power generation of the piezoelectric unit array. However, with a small stress difference, units in a parallel connection can obtain high energy conversion efficiency. Additionally, loaded with the matched impedance of 275.0 kΩ at 10.0 kN and 10.0 Hz, the proposed device reached a maximum output power of 84.3 mW, which is enough to supply the low-power sensors. Moreover, the indoor load test illustrates that the electrical performance of the piezoelectric device was positively correlated with the simulated loads when loaded with matched resistance. Furthermore, the electrical property remained stable after the fatigue test of 100,000 cyclic loads. Subsequently, the field study confirmed that the developed piezoelectric device had novel piezoelectric properties with an open-circuit voltage of 190 V under an actual tire load, and the traffic parameters can be extracted from the voltage waveform.

The aim of this paper is to propose a simple empirical prediction model for temperature gradients within concrete slabs of jointed plain concrete pavements (JPCPs) based on data collected by the Pavement Conditions Monitoring System at Shanghai Pudong International Airport. Temperature data (7,056 data sets) were obtained at the center and corner of the concrete slab and evaluated via statistical analysis. Equivalent linear temperature gradients were employed to quantify the nonlinear temperature profiles throughout the depth of the concrete slab. The surface temperature was obtained via the regressed quadratic function of the temperature profile. For simplicity and effectiveness, concrete slab thickness, surface temperature, air temperature, and time were selected as the input variables. A simple empirical model for predicting the temperature gradient in the concrete slab was developed using multiple regression analysis and validated by field temperature data. The results show no significant difference between the temperatures measured at the center and corner of the concrete slab. Hence, measurement location appears to have little effect on the monitoring of temperature in JPCPs. The results also show that the calculated surface temperature is valid for establishing the empirical model. Moreover, the statistical analysis results indicate that the empirical model fits the data well and all the coefficients in the model are significant at 5% significance. The final results of the model validation demonstrate that the proposed empirical model is reliable and can be conveniently used to predict the temperature gradients within concrete slabs of JPCPs.

GRAPHICAL ABSTRACT Abstract An amphiphilic paradodecatungstate catalyst, [(C₁₈H₃₇)₂N(CH₃)₂]₉[NaH₂W₁₂O₄₂] was prepared and characterized by Fourier transform infrared spectroscopy, UV–visible spectrum, differential thermal analysis, and thermogravimetric analysis. The amphiphilic catalyst exhibits very high catalytic activity that dibenzothiophene (DBT) in model diesel can be oxidized into dibenzothiophene sulfones using hydrogen peroxide as an oxidant. The reactivity of sulfur compounds decreased in the order of DBT > 4,6-DMDBT > BT > 5-MBT. The reaction rates of these sulfur compounds are sensitive to the electron density on sulfur atoms and the steric hindrance of the substituted groups of sulfur compounds. The sulfur level of a commercial diesel after desulfurization can drop from 200 ppm to about 12 ppm.