Risk analysis for urban excavation: a FAHP-VIKOR hybrid method

Figures & data

Table 1. Accident cases of foundation pit collapse from 2020 to 2021.

Date	Event	Cause	Casualty
June 3, 2020	Foundation pit collapse in Shenbei New District, Shenyang City, Liaoning Province.	Failure to take the required support and protection measures during slope excavation or for side walls	4 deaths
June 4, 2021	Foundation pit collapse in Yannan high tech Zone.	Failure to take effective safety measures, such as slope protection, to prevent collapse	1 death
August 5, 2021	Foundation pit collapse in Xiangxi high tech Zone, Hunan Province.	The construction site was buried due to landslides, falling mud and sand	4 deaths and 7 minor injuries
October 2, 2021	Foundation pit collapse in Linping District, Hangzhou City, Zhejiang Province.	Failure to implement the special construction plan	2 deaths
December 3, 2021	Foundation pit collapse in Nanhu watershed, Guangzhou, Guangdong Province.	The soil was soft and no supporting measures were adopted	1 death

Figure 1. Keyword co-occurrence knowledge graph: (a) multi-criteria decision-making (MCDM) method correlation diagram; (b) MCDM research heat map for 2019–2021.

Figure 2. Excavation risk assessment and management framework.

Table 2. Risk level implication.

Risk level	LV1	LV2	LV3	LV4	LV5
Assessment	Very low risk	Low risk	Median risk	High risk	Very high risk

Table 3. Reciprocal of triangular fuzzy numbers and their meanings (Adapted from Lyu et al. 2019).

Degree of importance	RFN	TFN	RTFN
Equally important	1	(1,1,1)	(1,1,1)
Almost equally important	1′	(1,1,3)	(1/3,1,1)
In between	2′	(1,2,4)	(1/4,1/2,1)
Slightly important	3′	(1,3,5)	(1/5,1/3,1)
In between	4′	(2,4,6)	(1/6,1/4,1/2)
important	5′	(3,5,7)	(1/7,1/5,1/3)
In between	6′	(4,6,8)	(1/8,1/6,1/4)
Obviously important	7′	(5,7,9)	(1/9,1/7,1/5)
In between	8′	(6,8,10)	(1/10,1/8,1/6)
Extremely important	9′	(7,9,11)	(1/11,1/9,1/7)

Figure 3. Triangular membership function (F₁ > F₂). (Adapted from Lyu et al. 2019).

Table 4. The values of RI for judgment matrices of order 1 to 9.

n	1	2	3	4	5	6	7	8	9
RI	0	0	0.52	0.89	1.12	1.26	1.36	1.41	1.46

Figure 4. Geographical location of the foundation pit.

Figure 5. Accident location: (a) foundation pit plan; (b) foundation pit details (adapted from Baidu map).

Figure 6. Collapse accident in the Guimintou foundation pit: (a) retaining structure failure; (b) parking shed on the slope (Chutian City Daily (CCD), 2022).

Figure 7. Meteorological data of Nanning in May (Tian Qi Website (TQW) 2022).

Table 5. Interval division of influential factors.

Factor	LV1	LV2	LV3	LV4	LV5
Groundwater level (X11)	[20,16]	[16,12]	[12,8]	[8,4]	[4,0]
24-hour precipitation (X12)	[0,10]	[[10,25]	[25,50]	[50,100]	[100,250]
Soil composition (X13)	[20,25]	[15,20]	[10,15]	[5,10]	[0,5]
Surface settlement (X21)	[0,2.5]	[2.5,5]	[5,7.5]	[[7.5,10]	[10,12.5]
Distance from surrounding buildings (X22)	[40,50]	[30,40]	[20,30]	[10,20]	[0,10]
Construction technique (X31)	[80,100]	[60,80]	[40,60]	[20,40]	[0,20]
Management quality (X32)	[80,100]	[60,80]	[40,60]	[20,40]	[0,20]
Depth of excavation (X41)	[0,10]	[10,20]	[20,30]	[30,40]	[40,50]
Stacking load (X42)	[0,20]	[20,40]	[40,60]	[60,80]	[80,100]
Dynamic load (X43)	[0,20]	[20,40]	[40,60]	[60,80]	[80,100]

Figure 8. Hierarchy chart of the potential safety risks in the Guimintou foundation pit.

Figure 9. Weight chart of evaluation index and risk factors: (a) weight of evaluation index. (b) Weight of risk factors.

Table 6. Triangular fuzzy matrix.

Index layer	N1	N2	N3	N4	λmax	CR
N1	[1.00, 1.00, 1.00]	[0.33, 1.00, 1.00]	[0.20, 0.33, 1.00]	[0.25, 0.50 ,1.00]	4.106	0.040
N2	[1.00, 1.00, 3.00]	[1.00, 1.00, 1.00]	[0.25, 0.50, 1.00]	[0.25, 0.50, 1.00]
N3	[1.00, 3.00, 5.00]	[1.00, 2.00, 4.00]	[1.00, 1.00, 1.00]	[1.00, 1.00, 3.00]
N4	[1.00, 2.00, 4.00]	[1.00, 2.00, 4.00]	[0.33, 1.00, 1.00]	[1.00, 1.00, 1.00]
Factor layer	X11	X12	X13		3.065	0.062
X11	[1.00, 1.00, 1.00]	[0.25, 0.50 ,1.00]	[0.33, 1.00, 1.00]
X12	[1.00, 2.00, 4.00]	[1.00, 1.00, 1.00]	[1.00, 2.00, 4.00]
X13	[1.00, 1.00, 3.00]	[0.25, 0.50 ,1.00]	[1.00, 1.00, 1.00]
Factor layer	X21	X22			No consistency check
X21	[1.00, 1.00, 1.00]	[1.00, 2.00, 4.00]
X22	[0.25, 0.50 ,1.00]	[1.00, 1.00, 1.00]
Factor layer	X31	X32			No consistency check
X31	[1.00, 1.00, 1.00]	[0.25, 0.50 ,1.00]
X32	[1.00, 2.00, 4.00]	[1.00, 1.00, 1.00]
Factor layer	X41	X42	X43		3.093	0.089
X41	[1.00, 1.00, 1.00]	[0.25, 0.50 ,1.00]	[1.00, 2.00, 4.00]
X42	[1.00, 2.00, 4.00]	[1.00, 1.00, 1.00]	[1.00, 3.00, 5.00]
X43	[0.25, 0.50 ,1.00]	[0.20, 0.33, 1.00]	[1.00, 1.00, 1.00]

Figure 10. Risk level chart.

Table 7. Scoring table for risk factor of the excavation.

Risk factor	X11	X12	X13	X21	X22	X31	X32	X41	X42	X43
rate	8	25	20	12.5	0	40	40	15	100	40

Table 8. Square normalization matrix.

Factor	X11	X12	X13	X21	X22	X31	X32	X41	X42	X43	S	R	Q
LV1	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
LV2	0.008	0.003	0.010	0.028	0.014	0.022	0.043	0.021	0.027	0.012	0.188	0.043	0.194
LV3	0.015	0.007	0.020	0.056	0.028	0.043	0.086	0.042	0.055	0.024	0.378	0.086	0.389
LV4	0.023	0.015	0.031	0.085	0.042	0.065	0.130	0.063	0.082	0.036	0.570	0.130	0.585
LV5	0.030	0.030	0.041	0.113	0.056	0.086	0.173	0.084	0.110	0.048	0.770	0.173	0.785
LV6	0.038	0.074	0.051	0.141	0.070	0.108	0.216	0.105	0.137	0.060	1.000	0.216	1.000

Table 9. Boundary standards of risk factor grade.

	LV1		LV2		LV3		LV4		LV5
Standard value	L	R	L	R	L	R	L	R	L	R
	0.00	0.194	0.194	0.389	0.389	0.585	0.585	0.785	0.785	1.00

Figure 11. Comparison of FAHP, AHP, and PC weight results.

Figure 12. Comparison of calculation results between FAHP-VIKOR and FAHP-TOPSIS.

Lyu HM, Shen SL, Zhou A, Yang J. 2019. Perspectives for flood risk assessment and management for mega-city metro system. Tunnell Undergr Space Technol. 84:31–44. doi: 10.1016/j.tust.2018.10.019.

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Chutian City Daily (CCD). 2022. A slope collapse at a construction site in Nanning caused damage to dozens of electric vehicles in the community, which was hidden trouble a year ago. [accessed 2022 May 23] https://baijiahao.baidu.com/s?id=1733621796335384198&wfr=spider&for=pc (in Chinese).

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Tian Qi Website (TQW). 2022. Nanning historical weather in May. [accessed 2022 May 31] http://lishi.tianqi.com/nanning/202205.html (in Chinese).

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Data availability

Data will be made available on request.