Shield Equipment Optimization and Construction Control Technology in Water-Rich and Sandy Cobble Stratum: A Case Study of the First Yellow River Metro Tunnel Undercrossing

Table 1

Cobbles of particle-size distributions.

Type	Statistical indicators	Grains composition (%)								Uniformity coefficient (CU)
		Grains sizes (mm)
		100∼60	60∼40	40∼20	20∼2	2∼0.5	0.5∼0.25	0.25∼0.75	0.75∼0.005
Cobble ()	Minimum value	0	8.8	9.4	3.1	0.6	0.5	0.2	0	2.21
	Maximum value	42.3	68.3	32.7	25.7	13.9	12.5	9.4	12	310.73
	Average value	11.63	30.84	22.11	15.19	7.09	5.36	4.87	2.91	113.1
	Standard deviation	12.890	11.166	5.802	4.905	3.506	3.033	2.458	2.763	66.129
	CV	1.109	0.362	0.263	0.323	0.494	0.566	0.504	0.949	0.585
	Count	37
Cobble ()	Minimum value	0	13.4	7.5	2.3	0.5	1	0.8	0.01	9.18
	Maximum value	34.5	75.1	38.7	21.24	13.7	11.8	8.5	13.6	1027.13
	Average value	6.44	32.73	24.65	13.87	7.7	5.56	4.09	4.87	213.06
	Standard deviation	8.6	12.9	6.33	5.39	4.1	2.89	1.69	3.71	239.56
	CV	1.335	0.394	0.257	0.389	0.533	0.511	0.412	0.762	1.24
	Count	24