Analysis of labour accidents caused by slope failure during slope cutting and application of a rapid checklist for risk management in Japan

Figures & data

Figure 1. Annual number of labour accidents during construction works.

Figure 2. Relationship between slope failure risk and working items during the construction process of a retaining wall.

Figure 3. Number of personnel present at the time of accident [23].

Figure 4. Classification of slope failure accidents by construction methods [23].

Figure 5. Accident site of concrete frame construction work [25].

Figure 6. Accident site of frame dismantling work [25].

Figure 7. Classification of slope failure accident causes of death [23].

Table 1. Design and construction procedures checklist [27].

Name of construction site
Position	Factor	Item	Phenomenon (detail to be confirmed)	1. Investigation and design	2. Construction planning	3. Stack out	Excavation
							4. Before work	5. End
Remaining slope	Topography	Landslide area	Cracks, steps and contour disturbance exist	Yes / No / Unknown	Yes / No / Unknown	Yes / No / Unknown	Yes / No	Yes / No
		Floating and boulders	Unstable conditions	Yes / No / Unknown	Yes / No / Unknown	Yes / No / Unknown	Yes / No	Yes / No
		Overhangs	Fresh collapse is observed	Yes / No / Unknown	Yes / No / Unknown	Yes / No / Unknown	Yes / No	Yes / No
	Surrounding conditions	Vegetation	Different from surrounding vegetation or bamboo groves	Yes / No / Unknown	Yes / No / Unknown	Yes / No / Unknown	Yes / No	Yes / No
		Structures	Cracks or other deformities exist	Yes / No / Unknown	Yes / No / Unknown	Yes / No / Unknown	Yes / No	Yes / No
Cutting slope	Geology, etc. (soil and rock quality)	Colluvial deposit, weathering slope	Soil is uneven and soft	Yes / No / Unknown	Yes / No / Unknown	Yes / No / Unknown	Yes / No	Yes / No
		Sandy soil, etc.	Soil type is particularly vulnerable to erosion	Yes / No / Unknown	Yes / No / Unknown	Yes / No / Unknown	Yes / No	Yes / No
		Fast weathering rock	Rock is sedimented on the surface	Yes / No / Unknown	Yes / No / Unknown	Yes / No / Unknown	Yes / No	Yes / No
		Fractured rock	Brittle rock with many cracks	Yes / No / Unknown	Yes / No / Unknown	Yes / No / Unknown	Yes / No	Yes / No
	Geological structure	Dip slope	Easily detached by dip slope	Yes / No / Unknown	Yes / No / Unknown	Yes / No / Unknown	Yes / No	Yes / No
		Fracture zones, etc.	Weak layer exists and may slip	Yes / No / Unknown	Yes / No / Unknown	Yes / No / Unknown	Yes / No	Yes / No
	Spring water	Groundwater	Constant and large amount of spring water, turbidity in spring water	Yes / No / Unknown	Yes / No / Unknown	Yes / No / Unknown	Yes / No	Yes / No
	Freezing	Freezing and thawing	Significant freezing and thawing	Yes / No / Unknown	Yes / No / Unknown	Yes / No / Unknown	Yes / No	Yes / No
	Disaster record	Slope failure	History of collapse at nearby construction sites	Yes / No / Unknown	Yes / No / Unknown	Yes / No / Unknown	Yes / No	Yes / No
Remarks	If ‘Yes’, describe the situation and response
Day/month signature				/	/	/	/	/
Safety of construction is assured, day/month signature				/	/	/	/	/

Note: Table translated by the author.

This checklist is intended for checking the outcrop of the ground to be excavated (1. Investigation and design; 2. Construction planning), surface (3. Stake out), interior (4. Before excavation; 5. After excavation), and slope conditions that require special attention. If the answer to any of the items is ‘Yes’, the safety aspect should be examined to ensure the safety of construction site, and measures such as the safe cut-and-fill arrangement should be taken before proceeding to the next stage.

This checklist is used for excavation work where the excavation height of the cut is less than 10 m.

Table 2. Daily checklist [27].

		/	/	/
Day/month (A: before starting slope-cutting work, B: at the end of work, C: during heavy rain, D: after earthquakes greater than a mid-level quake, E: others)		()	()	()	Remarks
Check item	(1) The cut slope does not adjust to the stack out
	(2) New cracks were found in the cutting slope
	(3) Deformation was found in the cut and toe of the slope
	(4) Fallen rocks were found at the bottom of the slope
	(5) Slope collapse was found as a part of the cut slope
	(6) Ground water (spring water) flows in the cut slope
	(7) Loose stones or boulders were found in the cut slope
	(8) Degree of inclination of trees in the local area has changed
	(9) Deformation was found in the nearby structures
	If the checking of items (10) and (11) below results in a ‘o’, make necessary repairs as soon as possible. (It is not necessary to move to the ‘Ground deformation checklist’ for improvement.)
	(10) Drainage is not smooth during rainfall
	(11) Unusual slope protection measures (sheeting) during rainfall
	(12) Phenomena in the design and construction procedures checklist appeared
	(13) Others
Remarks	Location, time, deformation status, etc.
Inspector signature
Checker signature

Note: Table translated by the author.

This checklist is used to identify any early deformation of slopes to predict slope failure and for prevention of labour accidents.

This checklist is used in the following cases: before starting slope-cutting work, construction of retaining walls on cut slopes, at the end of work, during heavy rain and after earthquakes greater than a mid-level quake.

If any of the check results are applicable, mark an ‘o’ for that item; if not, mark an ‘x’.

If any check result is marked ‘o’, the slope deformation must be reviewed using the ‘Ground deformation checklist’, and the necessary countermeasures must be implemented (excluding (10) and (11)).

Figure 8. Field site before disaster restoration work.

Figure 9. Plane view of the field site.

Figure 10. Typical cross-section of the slope and geometry.

Figure 11. Cracks found in the retaining wall before construction.

Figure 12. Small collapses caused by groundwater during excavation.

Table 3. Design and construction procedures checklist at this field site.

Figure 13. Installation of measurement instrumentation on the site.

Figure 14. IT tilt sensor (AKEBONO Brake Industry Co., Ltd., Japan): (a) general appearance; (b) tilt sensor installed in the ground.

Table 4. Excavation and nailing phases during this construction.

Event	Date
Excavation first stage	May 10, 2019
Nailing first stage	May 25, 2019
Nailing second stage	May 25–28, 2019
Nailing third stage	May 31, 2019
Excavation second stage	June 7, 2019
Nailing fourth stage	June 20, 2019
Nailing fifth stage	June 25, 2019

Figure 15. Time histories of two tilt sensors including some main events: excavation, nailing, rainfall, etc.

Figure 16. During and before the construction at the field monitoring site: (a) before work; (b) after first excavation; (c) after first and second nailing works; (d) after second excavation; (e) third nailing after rain; (f) finished nailing works.

Itoh K, Toyosawa Y, Tamrakar SB, et al. Analysis of labor accidents caused by slope failure. J Jpn Landslide Soc. 2005;41(6):585–594. doi:10.3313/jls.41.6_585

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Toyosawa Y, Timpong S, Itoh K, et al. Preventive strategy for labor accidents caused by slope failures. In: Japan Society for Safety Engineering, editor. Proceedings of the Asia Pacific Symposium on Safety; 2009 October 20–23; Okasa, Japan: Osaka Academia; 2009. p. 139–142.

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National Institute of Occupational Safety, Japan (JNIOSH). Report of commotions of inquiry on prevention of labor accidents caused by slope failure [Internet]; 2010 [cited 2023 Apr 14]. Japanese. Available from: https://www.jniosh.johas.go.jp/publication/houkoku/houkoku_2010_01.html

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