**5. Discussion**

As mentioned above, *OCR* can not only directly reduce the thermal pore water pressure (Equation (6)), but it can also change the magnitude of the thermal pore water pressure by affecting the value of *Λ* (Equations (10) and (11)). However, the effect of *OCR* on *Λ* is often ignored in existing calculation methods [9,26], which may be the main reason for overestimating the thermal pore water pressure of highly overconsolidated soil. To quantitatively analyze the effect of *Λ* on the thermal pore water pressure, two cases are given here, namely, Case 1: the predicted results without considering the variation of *Λ* (*Λ* = 6.5), and their comparison with the experimental results; and Case 2: the predicted results considering the variation of *Λ* (*Λ* = 5.4, 5.0, and 3.8), and their comparison with the experimental results. The effect of *Λ* on the thermal pore water pressure is analyzed by comparing the coincidence between experimental results and predicted results. Figure 4a,b show the comparison of experimental results and predicted results for the two cases.

**Figure 4.** Comparison between experimental results and predicted results of (**a**) Case 1; (**b**) Case 2.

From Figure 4a, it can be observed that the predicted results without considering the variation of *Λ* will seriously overestimate the thermal pore water pressure. For clays with *OCR* equal to 10 and 30, the coefficients of determination (*R*2) of predicted results are both 0. When the change in temperature is 35 ◦C, the difference between the experimental results and predicted results reaches 61.5% for the clay with *OCR* equal to 10, and the difference reaches 127.2% for the clay with *OCR* equal to 30. However, from Figure 4b, it can be found that the coincidence between the predicted results considering the variation of *Λ* and experimental results was greatly improved. Especially, when *OCR* is equal to 30, the accuracy of the predicted results was improved by 92.7%, which means that the variation of *Λ* with *OCR* cannot be ignored when predicting the thermal pore water pressure inside the highly overconsolidated clay.
