Ordinance on Industrial Safety and Health
Ministry of Labour Ordinance No. 32 of September 30, 1972
Latest Amendments:
Ministry of Health, Labour and Welfare Ordinance No. 47 of March 30, 2007
In Japanese
掲載日：2008.03.28
Part II Safety Standards
Chapter VI Prevention of Dangers in Excavating Work, etc.
Section 1 Open-Cut Excavating Work
Subsection 1 Time and Procedure of Excavating Work, etc.
Article 355 (Investigation on Work Place, etc.)
- (1) The employer shall, in the case of carrying out an excavating work of natural ground, and when it is liable to cause dangers to workers due to collapse of natural ground, broken underground-installed objects, etc., investigate in advance the natural ground of the work place and its surroundings as to the following matters by boring or other suitable methods, and determine the time and procedures of excavation on the in conformity with what is known by the investigation and carry out by the determinations thereof:
- (i) Landform, nature of the soil and conditions of strata.
- (ii) Existence and conditions of cracks, water content, spring water and freezing.
- (iii) Existence and conditions of underground-installed objects, etc.
- (iv) Existence and conditions of high-temperature gas and vapor.
Article 356 (Standard of Gradient of Excavation Surfaces)
- (1) The employer shall, when carrying out excavating work of natural ground (excluding natural ground composed of rock beds without cracks that cause collapse or fall of rocks, natural ground composed of sand, and natural ground in a condition which is liable to collapse due to blasting etc., hereinafter the same shall apply in this Article) by the method of manual excavation (meaning the method of excavation without excavating machines such as power shovel and tractor shovel; hereinafter the same shall apply in next Article), make the gradient of the excavation surface (in the case that there is a horizontal step with a depth of 2 m or more on the excavation surface, each excavation surface divided by the said horizontal step; the same shall apply hereinafter) the value listed in the right column of the following table or less corresponding to the type of the ground listed in the left column and the height of the excavation surface listed in the middle column of the same table, respectively:
Type of the natural ground Height of the excavation surface (m) Gradient of the excavation surface (degree) natural ground composed of rock beds or hard clay Less than 5 90 5 or more 75 Other natural ground Less than 2 90 2 or more but less than 5 75 5 or more 60 - (2) In the case prescribed in the preceding paragraph, when it is impossible to calculate the gradient due to some parts of the excavation surface differ in slope from other parts, the slopes of each part of the excavation surface shall be so maintained that the danger of collapse may not become greater than that as prescribed in the same paragraph.
Article 357
- (1) The employer shall, when carrying out an excavating work of natural ground composed of sand or of natural ground in a condition which is liable to collapse due to blasting, etc., by manual excavation, comply with the following provisions:
- (i) For natural ground composed of sand, to make the gradient of the excavation surface 35 degrees or less, or make the height of the excavation surface less than 5 m.
- (ii) For natural ground in a condition which is liable to collapse due to blasting, etc., to make the gradient of the excavation surface 45 degrees or less, or make the height of the excavation surface less than 2 m.
- (2) The provisions of item (ii) of the preceding Article shall apply mutatis mutandis to the case that it is impossible to calculate the gradient because some parts of the excavation surface of the natural ground set forth in the preceding paragraph differ in slope from other parts.
Article 358 (Checkup)
- (1) The employer shall, when carrying out the work of open-cut excavation, take the following measures to prevent workers from dangers due to collapse of natural ground or fallen earth and rocks:
- (i) To designate a checker and have the said checker carry out a checkup on the natural ground of the work place and its surroundings before commencing the work for the day, after a heavy rain and an earthquake of medium shock or heavier as to the existence and conditions of loose stones and cracks, and changes in water content, spring water and freezing.
- (ii) To designate a checker and have the said checker carry out a checkup on the existence and conditions of loose stones and cracks, after blasting operations, at places where the said blasting operations have been carried out and their surroundings.
Article 359 (Appointment of an Operations Chief of Excavating Natural Ground)
- (1) The employer shall, as regards the work set forth in item (ix) of Article 6 of the Order, appoint an operations chief of excavating natural ground from the persons who have completed the skill training course for operations chief of excavating natural ground and shoring.
Article 360 (Duties of an Operations Chief of Excavating Natural Ground)
- (1) The employer shall have an operations chief of excavating natural ground carry out the following matters:
- (i) To decide a work method and supervise the work directly.
- (ii) To check an instrument and a tool, and remove defective ones.
- (iii) To monitor the use of a safety belt, etc., and a safety helmet.
Article 361 (Prevention of Dangers Due to Collapse of Natural Ground, etc.)
- (1) The employer shall, in the case of carrying out the work of open-cut excavation, and when it is liable to cause dangers to workers due to collapse of natural ground or fallen earth and rocks, take measures to prevent dangers, such as setting up shoring, setting up protective nets, prohibiting workers from entering etc., in advance.
Article 362 (Prevention of Dangers Due to Underground-Installed Objects, etc.)
- (1) The employer shall, in the case of carrying out the work of open-cut excavation at a place adjacent to underground-installed objects, etc., or buildings of brick walls, concrete block walls, retaining walls, etc., and when it is liable to cause dangers to workers due to their collapse, not carry out the work unless measures to prevent dangers have been taken, such as reinforcing and removing them.
- (2) The measure set forth in the preceding paragraph shall, in the case that it is liable to cause dangers to workers due to breakage of gas conduits exposed by open-cut excavation work, be such measures as protection of the said gas conduits by suspending protection, supporting protection, etc., or removal of the said gas conduits, etc.
- (3) The employer shall, as regards the works for the protection of gas conduits prescribed in the preceding paragraph, designate a person to direct the said work, and have the said work carried out under the direct supervision by the said person.
Article 363 (Prohibition of the Use of Excavating Machine, etc.)
- (1) The employer shall, in the case of carrying out the open-cut excavation work and when it is liable to cause dangers to workers due to breakage of gas conduits, underground electric line or other underground structures by the use of excavating machine, loading and transporting machines, not use the said machines.
Article 364 (Travelling Route, etc., of Transporting Machines, etc.)
- (1) The employer shall, when carrying out the open-cut excavation work, determine in advance an travelling route for a transporting machine, a excavating machine and a loading machine (excluding a vehicle type construction machine and a vehicle type material handling machine, etc.; hereinafter referred to as “transporting machine, etc.” in this Chapter), and the method for those machines of entering and leaving from the loading and unloading place of the earth and rocks, and make them known to the workers concerned.
Article 365 (Arrangement of a Guide)
- (1) The employer shall, in the case where carrying out the open-cut excavation work, and when a transporting machine, etc., approach the work place by backing or when it is liable to cause falling, arrange a guide and have the said person guide the said machines.
- (2) The operator of the transporting machine, etc., set forth in the preceding paragraph shall follow the instruction given by the guide set forth in the same paragraph.
Article 366 (Wearing of a Safety Helmet)
- (1) The employer shall, when carrying out the work of open-cut excavation, have the worker engaging in the said work wear a safety helmet in order to prevent workers from dangers due to flying or falling objects.
- (2) The worker engaging in the work set forth in the preceding paragraph shall wear the safety helmet set forth in the same paragraph.
Article 367 (Maintenance of Illumination)
- (1) The employer shall, as regards the place where carrying out the work of an open-cut excavation, maintain necessary illumination for carrying out the said work safely.
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