Characteristics of Gravelly Granite Residual Soil in Bored Pile Design: An In Situ Test in Shenzhen

Table 4

Summary of back-analyzed factors for the shaft resistance.

	Depth	Average SPT-N	Undrained shear strength (Su)	Measured ultimate unit skin friction (qsu)	qsu/N	β	Soil
		blows/30 mm	kPa	kPa
TP-1; (RD+S)	3–5 m	12	—	51.95	4.33	0.77	GRS
	5–7.5 m	16	52.22	52.12	3.26	0.50	GRS
TP-2; (RD+S)	7.5–13 m	23	75.26	74.46	3.24	0.51	GRS
	13–17.5 m	32	—	58.05	1.81	0.29	GRS
	17.5–18 m	54	125.13	87.61	1.62	0.39	GRS
TP-3; (RD+S)	5–10 m	34	64.99	112.80	3.32	0.88	GRS
	10–13 m	22	79.13	52.32	2.38	0.28	GRS
	13–16 m	23.5	—	82.60	3.51	0.38	GRS
	16–18 m	25	—	37.06	1.48	0.15	GRS
	18–20.5 m	60	150.67	118.47	1.97	0.45	GRS
	20.5–22.5 m	73	—	65.53	0.90	0.23	GRS
TP-4; (RD+C)	5–7.5 m	20	65.97	98.70	4.94	0.95	GRS
TP-5; (RD+C)	5–13 m	25.7	70.14	78.52	3.06	0.67	GRS
	13–17.5 m	31.5	90.26	72.26	2.29	0.41	GRS
TP-6; (RD+C)	3–7.5 m	24	56.04	96.70	4.03	1.07	GRS
	7.5–10 m	27	72.80	110.21	4.08	0.76	GRS
	10–13 m	31	94.42	85.49	2.76	0.50	GRS
	13–16 m	26	104.84	60.98	2.35	0.30	GRS
	16–18 m	38	134.39	106.88	2.81	0.47	GRS
	18–20.5 m	41	—	154.84	3.78	0.62	GRS
	20.5–22.5 m	57	161.61	166.26	2.92	0.61	GRS

GRS: granite residual soil.