# A Case Study on Distresses of Concrete Pavements Supported on a Retaining Wall
## 3 Evaluation of the Performance of the Subject Section
### Evaluation of Soil Conditions in MSE Wall
#### 3.3.1 Soil Modulus from DCP Test and CPT
\begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Test Location**} & **Investigation Depth below** & **Weighted Average Value of** \\  & **Pavement Surface** & **Resilient Modulus** \\  & **[in (m)]** & **[ksi (MPa)]** \\ \hline \hline \multicolumn{3}{c}{Along the outside lane left wheel path from the east to the west of the subject section} \\ \hline DCPS OL LWP & 101.4 (2.58) & 10.3 (71.0) \\ \hline DCP3 OL LWP & 102.7 (2.61) & 10.2 (70.3) \\ \hline DCP6 OL LWP & 102.0 (2.59) & 5.3 (36.5) \\ \hline DCP7 OL LWP & 101.6 (2.58) & 7.0 (48.3) \\ \hline DCP4 ML (Control) & 82.8 (2.10) & 15.8 (108.9) \\ \hline DCP8 OL LWP (Control) & 81.5 (2.07) & 17.8 (122.7) \\ \hline \multicolumn{3}{c}{At Location 2 from the outside lane to the inside lane} \\ \hline DCP2 OL RWP & 93.3 (2.37) & 14.0 (96.5) \\ \hline DCP2 OL LWP & 96.7 (2.46) & 9.8 (67.6) \\ \hline DCP2 ML & 88.8 (2.26) & 4.4 (30.3) \\ \hline DCP2 IL & 91.1 (2.31) & 7.9 (54.5) \\ \hline DCP2 IS & 81.4 (2.07) & 16.4 (113.1) \\ \hline \multicolumn{3}{c}{At Location 3 from the outside lane to the inside lane} \\ \hline DCP3 OL RWP & 98.5 (2.50) & 17.4 (120.0) \\ \hline DCP3 OL LWP & 102.7 (2.61) & 10.2 (70.3) \\ \hline DCP3 ML & 98.8 (2.51) & 4.8 (33.1) \\ \hline DCP3 IL & 102.7 (2.61) & 6.8 (46.9) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Weighted average value of resilient modulus at each DCP location. Figure 14: _Cont._  
As shown in Table 1, the maximum DCP investigation depth was 102.7 in (2.6 m) at Location 3, whereas the height of the MSE wall at Location 3 was about 17.8 ft (5.4 m). Figure 15 presents a plan set drawing that shows the height of the MSE wall at the CPT locations. To characterize soil conditions in the MSE wall for the entire height, as well as soils beneath the MSE wall (i.e., founding soils), CPTs were conducted through drilled holes (the depths of drilled holes were about 31 in (0.79 m)) at Locations 3, 5, 6, 7, and 8 in the close proximities of the corresponding DCP tests, typically within 2 ft (0.6 m) of each other. The maximum CPT investigation depth was 46.7 ft (14.2 m) below the pavement surface at Location 5. Figure 14: Resilient moduli estimated via DCP tests: (**a**) along the outside lane left wheel path (OL LWP) from east to west of the subject section, (**b**) at Location 2 from the outside lane to the inside lane, and (**c**) at Location 3 from the outside lane to the inside lane. One resistances from all five CPTs are plotted in Figure 16. It is observed that cone resistance values from a depth of about 2.5 ft (0.8 m) to 20 ft (6.1 m) below the pavement surface are typically less than 15 tsf (1.4 MPa). Also, CPT8 (control section) shows the largest cone resistance values, and CPT7 shows the smallest values. Variations in cone resistance up to a depth of 9 ft (2.7 m), which was about the maximum depth of the DCP tests, are also presented in Figure 16.  
Figure 16: Cone resistance vs. penetration depth from all five CPTs. Figure 15: Heights of MSE wall at the CPT locations. The results of CPTs are commonly used to estimate the engineering properties of soils, such as friction angle and relative density for sandy soils and undrained shear strength for clayey soils [49]. Unfortunately, very limited research was conducted into the relationship between cone resistance and resilient modulus, and there are no well-accepted correlations between them in the literature. [PERSON] et al. [50] proposed a statistical model for predicting resilient modulus from a miniature cone resistance but acknowledged that more tests were needed to develop a general model because their study was limited to a specific soil type. Similarly, [PERSON] and [PERSON] [51] examined the feasibility of using CPT data to estimate resilient modulus through CPTs and laboratory tests and concluded that the statistical analysis model used by them was not sufficient to allow the use of CPT to measure resilient modulus in the field.