Safety evaluation of urban underground utility tunnel with the grey clustering method based on the whole life cycle theory

Figures & data

Figure 1. The construction scale in every year (2015–2020).

(Data source: China urban comprehensive pipe gallery market research and development prospect forecast report from 2021 to 2027 https://zhuanlan.zhihu.com/p/370086024, 2021–05-06.)

Figure 2. The main works at each stage of the life cycle of the urban underground utility tunnel.

Table 1. Safety classification standards of utility tunnel.

Safety level	Standards for the classification of safety levels
Very unsafe	There is serious damage to the structure, major accidents such as explosion and collapse have occurred, which has endangered the personal and property safety of residents
Less safe	The structure l is damaged, and there is a hidden danger of major accidents.
Basic safe	The structure is damaged, but it is operating normally at this stage, and there may be hidden danger of major accidents
Relatively safe	The structure is slightly damaged, it is operating well at this stage, and there is no hidden danger of major accidents.
Very safe	The structure is complete and runs well.

Table 2. Grey classification and value range.

Very unsafe	Less safe	Basic safe	Relatively safe	Very safe
[0, 60)	[60, 70)	[70, 80)	[80, 90)	[90, 100]

Figure 3. Graph of the triangular center-point mixed whitening weight functions.

Table 3. Sources of the whole life cycle safety evaluation indexes r of utility tunnel.

Safety factors	Literature sources
The overall urban planning, underground space and traffic.	Bu, Wang, and Jin et al. (2016)
Geological conditions	Li and Li (2019)
the completion of perfect laws and regulations.	Bu, Wang, and Jin et al. (2016)
The government to play a leading role, and the government’s support	Wang, Chen, and Li et al. (2018)
The huge investment of the utility tunnel is a huge burden on the government.	Liu and Li (2017)
The reasonable distribution of operation cost	Qiao, Liu, and Zhang et al. (2018)
The utility tunnel should be designed and constructed in combination with the underground space and traffic as well as the sponge city.	Tan, Chen, and Wang et al. (2016)
The key points of utility tunnel design include section design, passage size design, foundation buried depth design, node design and so on.	Gu, Zhang, and Ye (2018)
Compatibility of pipelines should be considered in the design. Sewage pipes should be designed separately.	Canto-Perello and Curiel-Esparza (2006)
In the design of the utility tunnel, the ancillary facilities such as escape, alarm, smoke exhaust, ventilation and lighting should be considered.	Canto-Perello and Curiel-Esparza (2013)
The pipeline with potential danger should be designed for disaster prevention, and corresponding safety measures should be taken.	Canto-Perello, Curiel-Esparza, and Calvo (2009)
The requirements of civil air defense.	Wang (2017)
Quality, cost and schedule risks. systematic risks (natural, policy, economic and social) and non-systematic risks (technology, management and decision-making).	Wei and Liu (2017)
Pipe corrosion.	Xu, Shao, and Wu (2014)
Harmful or combustible gas in operation	Chen, Zhao, and Xiao (2018)
The buried depth of the utility tunnel	Yang (2020)
Acts of sabotage and terrorism	Feng, Sun, and Wu et al. (2019)
The existing maintenance methods.	Jiang, Ren, and Xu et al. (2019)
Internet of Things, BIM, big data and other advanced technologies	Weng and Zhang (2018)
Natural disasters	Guo (2019)

Table 4. The whole life cycle safety evaluation index system of utility tunnel.

First-level indicators		Second -level indicators		Index explanation
A1	Planning	A11	Collaborative planning	The degree of collaborative planning
		A12	Preliminary investigation	The degree of detail of the preliminary investigation
		A13	Complete laws and regulations	The perfection degree of the laws and regulations
		A14	Government policy support	The degree of government policy support
		A15	Financing mode selection	Risks in choosing the financing model
		A16	Fee pricing mechanism	The reasonable degree of the pricing mechanism
A2	Design	A21	Collaborative design	The degree of collaborative design
		A22	Structure design	The degree of structural design
		A23	Internal pipeline design	The degree of internal pipeline design
		A24	Auxiliary facilities design	The degree of auxiliary facilities design
		A25	Disaster prevention design	The degree of disaster prevention design
		A26	Air defense design	The degree of air defense design
A3	Construction	A31	Insufficient cost risk	Insufficient cost risk during the construction
		A32	Schedule delay risk	Schedule delay risk during the construction
		A33	Construction quality risk	Construction quality risk during the construction
		A34	Construction technology level	Construction technology level during the construction
		A35	Human factor	Management and decision-making risks during the construction
		A36	Material equipment risk	Material and equipment supply risks during the construction
		A37	Engineering change risk	Engineering change risk during the construction
A4	Operation and maintenance	A41	Pipeline corrosion	Pipeline corrosion risk during the operation
		A42	Internal environmental safety	Internal environmental safety risk during the operation
		A43	External planning mistakes	External planning mistakes risk during the operation
		A44	Human sabotage	Human sabotage risk during the operation
		A45	Structural maintenance system	The perfection degree of the structural maintenance system during the operation
		A46	Intelligent technology application	The application degree of intelligent technology during the operation
		A47	Force majeure	Force majeure risks during the operation

Figure 4. Schematic diagram of underground utility tunnel.

Figure 5. Graph of the vertical section of standard section of branch line.

Table 5. The whole life cycle safety index system weight of utility tunnel.

First-level indicators	Weights $w_i$	Second -level indicators	Information entropy $H_j$	Weights$w_j$	Relative weights${\eta }_j$
A1		A11	0.8078	0.0344	0.1675
		A12	0.8350	0.0296	0.1441
	0.2054	A13	0.7865	0.0382	0.1860
		A14	0.8186	0.0325	0.1582
		A15	0.7853	0.0385	0.1874
		A16	0.8200	0.0322	0.1568
A2		A21	0.8038	0.0352	0.1478
		A22	0.7542	0.0440	0.1848
	0.2381	A23	0.7872	0.0381	0.1600
		A24	0.7956	0.0366	0.1537
		A25	0.7213	0.0499	0.2096
		A26	0.8087	0.0343	0.1441
A3		A31	0.8495	0.0270	0.0897
		A32	0.8077	0.0344	0.1143
		A33	0.5811	0.0750	0.2493
	0.3009	A34	0.7125	0.0515	0.1712
		A35	0.7807	0.0393	0.1306
		A36	0.7912	0.0374	0.1243
		A37	0.7973	0.0363	0.1206
A4		A41	0.8132	0.0335	0.1311
		A42	0.7844	0.0386	0.1510
		A43	0.7278	0.0488	0.1909
	0.2556	A44	0.7852	0.0385	0.1506
		A45	0.8179	0.0326	0.1276
		A46	0.8484	0.0272	0.1064
		A47	0.7966	0.0364	0.1424

Table 6. Whitenization weight values and comprehensive clustering coefficients of indices. (A₁₁-A₁₆).

							Comprehensive clustering coefficients
Indices	Scores	$f_j^1$	$f_j^2$	$f_j^3$	$f_j^4$	$f_j^5$	Grey category k1	Grey category k2	Grey category k3	Grey category k4	Grey category k5
A11	90	0.0000	0.0000	0.0000	0.5000	0.5000
A12	80	0.0000	0.0000	0.5000	0.5000	0.0000
A13	76	0.0000	0.0000	0.9000	0.1000	0.0000	0.0000	0.0000	0.3818	0.4250	0.1931
A14	76	0.0000	0.0000	0.9000	0.1000	0.0000
A15	90	0.0000	0.0000	0.0000	0.5000	0.5000
A16	86	0.0000	0.0000	0.0000	0.9000	0.1000

Table 7. Comprehensive grey clustering coefficient table.

	Very unsafe k1	Less safe k2	Basic safe k3	Relatively safe k4	Very safe k5
${\gamma }^k$	0.0147	0.0590	0.1674	0.4836	0.2753

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