Table 5.

Undrained cohesion and moisture content results after FTC based on the orthogonal experiment.

Runs	$x_1$ (%)	$x_2$ (%)	$x_3$ (mm)	$x_4$ (times)	$x_5$ (℃)	$x_6$ (kPa)	$y_C$(kPa)			$y_{\omega }$(%)
							$y_{c_U}$	$y_{c_M}$	$y_{c_L}$	$y_{{\omega }_U}$	$y_{{\omega }_M}$	$y_{{\omega }_L}$
0	20	90	–	5	− 15	30	5.3	3.6	5.8	24.2	24.2	24.6
1	28	96	35	9	− 5	50	6.4	3.3	3.3	27.3	27.6	27.6
2	28	93	30	7	− 10	40	5.3	3.6	3.4	25.7	25.9	26.6
3	28	90	25	5	− 15	30	6.5	4.3	6.6	23.2	24.6	24.2
4	28	87	20	3	− 20	20	6.0	7.6	7.0	22.7	22.1	22.4
5	28	84	15	1	− 25	10	8.6	8.1	7.6	23.1	22.5	22.8
6	24	96	30	5	− 20	10	5.3	3.3	3.3	25.2	25.6	25.2
7	24	93	25	3	− 25	50	7.7	8.1	7.6	25.4	24.7	25.3
8	24	90	20	1	− 5	40	7.9	9.7	8.9	23.1	23.0	23.1
9	24	87	15	9	− 10	30	5.3	4.6	4.4	24.9	26.5	26.8
10	24	84	35	7	− 15	20	5.6	5.1	3.1	26.2	26.5	26.8
11	20	96	25	1	− 10	20	6.4	7.5	6.4	23.7	23.3	23.7
12	20	93	20	9	− 15	10	5.6	4.7	4.5	24.9	26.4	26.5
13	20	90	15	7	− 20	50	5.3	5.0	4.9	25.8	25.9	27.3
14	20	87	35	5	− 25	40	7.6	5.4	7.0	24.3	24.6	24.4
15	20	84	30	3	− 5	30	5.3	5.0	5.1	22.6	22.4	22.5
16	16	96	20	7	− 25	30	9.8	8.4	8.3	23.6	25.5	25.8
17	16	93	15	5	− 5	20	8.5	7.4	6.3	24.8	25.2	25.9
18	16	90	35	3	− 10	10	6.5	10.2	8.5	24.8	23.9	24.2
19	16	87	30	1	− 15	50	6.5	7.5	6.6	25.7	25.1	25.7
20	16	84	25	9	− 20	40	5.2	3.2	3.0	24.8	26.4	26.6
21	12	96	15	3	− 15	40	6.5	8.5	7.1	23.2	23.0	23.2
22	12	93	35	1	− 20	30	6.4	6.3	6.3	22.5	21.1	21.3
23	12	90	30	9	− 25	20	9.7	8.2	7.8	25.3	26.4	27.8
24	12	87	25	7	− 5	10	7.7	7.2	5.9	24.8	25.6	25.7
25	12	84	20	5	− 10	50	6.4	4.2	4.1	23.5	24.0	25.4

where, $x_1$ is initial moisture content, %; $x_2$ is compaction degree, %; $x_3$ is reinforced spacing, mm; $x_4$ is number of FTC, times; $x_5$ is freezing temperature, ℃; $x_6$ is effective vertical stress, kPa; $y_{c_U}$, $y_{c_M}$ and $y_{c_L}$ are the undrained cohesion of the upper, middle and lower parts of the clay after FTC, kPa; $y_{{\omega }_U}$, $y_{{\omega }_M}$ and $y_{{\omega }_L}$ are the moisture content of the upper, middle and lower parts of the clay after FTC, %; There is no geogrid reinforcement of Run 0.