Prevention of ground subsidence by drilling work

• Drilling work: The drilling depth is 4 meters or more below the ground surface and the drilling area is 500 square meters or more
• Tunnel construction: Finished inner diameter 1.35 meters or more and a length of 100 meters or more

Brochure (land subsidence and excavation work-Regulations by excavation work-) (PDF: 301KB)

Precautions

1. The excavation area for the drilling work shall be the projected area.
2. Extension of tunnel construction includes shafts.
3. If the tunnel shape is not circular, etc., it will be eligible if the diameter of any of the tunnel finish cross-sectional shape is 1.35 meters or more.

About the following report, we can perform in Yokohama-shi electronic application, report service (outside site).

registration form (Form No. 29) (word: 16KB)
Guide (Preparation of drilling work in registration form) (PDF: 789KB)

Businesses that fall under the above excavation scale (construction prime contractor) must notify at least 30 days before the date on which the excavation work starts (in the case of excavation).

1. Name or Name, and in the case of Address, the name of the representative.
2. Location where drilling work is performed
3. Outline of drilling work (drilling area, drilling depth, construction type and method, construction period of underground part)
4. Other matters specified by rules (measurement plan for changes in the surrounding ground, drilling plan, drilling cross section, drilling longitudinal section)
5. attached documents (a) Guide map, b) soil survey materials, c) Reason for selection of drilling method (including auxiliary methods), e) Schedule

Precautions

1. In the measurement plan for changes in the surrounding ground, please describe the measurement items, frequency, location, management standards, management system, and response to abnormalities.
2. The "drilling method" refers to the method of retaining the case of excavation work, and the excavation method (shield, NATM, propulsion method, etc.) for tunnel construction.
3. "30 days before the start of excavation work" means to start when performing mountain retaining or digging up the ground, whichever comes first.

Drilling work change registration form (Form No. 30) (word: 28KB)

• Changedattached documents: Please notify us within 30 days from the date of the change.
• Changes toattached documents: Please notify us at least 30 days before the date of the change.

Drilling work completed registration form (Form No. 31) (word: 13KB)

When the excavation work has been completed, notify us within 30 days from that date.

1. When planning drilling work, select a method that has high water stoppage properties and minimizes the impact on the surrounding ground and groundwater level.
2. When conducting excavation work, if there is a risk of ground collapse, the ground surface may sink or subsidence, select an appropriate auxiliary method in advance to stabilize the ground.
3. During drilling work, efforts should be made for early detection of abnormalities not only in the drilling yard but also in the surrounding ground and structures, as well as observe groundwater level and ground changes. (Please keep the record of the fluctuation observations for 3 years.)
4. In the event of land subsidence due to the excavation work, necessary measures shall be taken, including temporary suspension of construction.

The mayor may provide necessary guidance and advice to companies performing excavation work to prevent land subsidence, and recommend that necessary measures be taken when there is a risk of land subsidence (when it occurs). there is.