8.4　Quality Inspection for Detecting Work

8.4.1　The investigation and detecting of underground pipeline shall conduct quality inspection and acceptance according to the specifications in Article 3.0.22 of this Code.The underground pipeline investigation and detecting quality checklist shall be filled out according to the specifications in Table E.0.3 of Appendix E of this Code.

8.4.2　The pipeline points which are no less than 5% of the total number of distinctive pipeline points or the concealed pipeline points at each zone shall be selected respectively for quality inspection by redetecting.The inspection sampling points shall be evenly distributed，and selected randomly by different operators at different time.The quality inspection shall include the inspection for geometrical accuracy and connection relation of pipeline points，and for pipeline attribute data investigation results.

8.4.3　Inspection for geometrical accuracy of pipeline points shall include the check on distinctive pipeline points and concealed pipeline points.Recheck of the burial depth of underground pipeline shall be made for distinctive pipeline points.For concealed pipeline points，recheck of the plane position and burial depth of underground pipeline shall be made.According to the redetecting results，the mean square error（mts）of plane position and the mean square error（mth）of burial depth of the concealed pipeline points，mean square error（mtd）of the measured burial depth，and tolerance（δts and δth）of the distinctive pipeline points，mts and 2mth shall not exceed 0.5 times of the tolerance（δts and δth），and mtd shall not exceed±2.5cm.

Where:

ΔSti——Plane position deviation of concealed pipeline point（cm）.

Δhti——Burial depth deviation of concealed pipeline point（cm）.

Δdti——Burial depth deviation of distinctive pipeline point（cm）.

δts——Tolerance of plane position in re-detecting for concealed pipeline point（cm）.

δth——Tolerance of burial depth in re-detecting for concealed pipeline point（cm）.

n1——Number of check points of concealed pipeline points.

n2——Number of check points of distinctive pipeline points.

hi——Burial depth（cm）of the pipeline center at all the inspected points，when hi＜100cm，take hi=100cm.

8.4.4　The concealed pipeline points shall undergo excavation check and shall comply with the following specifications:

1　Each zone shall be evenly distributed in the concealed pipeline points，and no less than 1% of the total number of concealed pipeline points and no less than 3 points shall be randomly selected for excavation check.When the zone is large，and the number of those excavated points selected at 1% exceeds 30，then only 30 points should be selected.

2　In case that the deviation of plane position and burial depth between the excavated pipeline point and the detected pipeline points exceeds the number of tolerance points specified in Article 3.0.22 of this Code，and is less than or equal to 10% of the total number of excavated points，the detecting work quality in the said zone shall be accepted.

3　In case that the number of over-tolerance points exceeds 10% of the total number of excavated points，and is less than or equal to 20%，then no less than 1% of the total number of concealed pipeline points shall be re-selected for excavation check.When the number of over-tolerance points in those two selection among excavated points is less than or equal to 10% of the total number of excavated points，the detecting work quality shall be accepted.

4　In case that the number of over-tolerance points exceeds 20% of the total number of excavated points，and the number of excavated points exceeds 10，then the detecting work quality in the said zone shall not be accepted.

5　In case that the number of over-tolerance points exceeds 20% of the total number of excavated points，and the number of excavated points is less than 10，the number of excavated points for excavation check shall be increased to more than 10，and quality inspection shall be done according to the aforementioned principles.

8.4.5　During underground pipeline detecting，in addition to the check on the plane position and burial depth of pipeline points，the attribute data investigation for the pipeline points shall also be inspected.In case of any missing or mistake found out，makeup and correction shall be made timely.

8.4.6　For the zone that fails in quality inspection，the causes of failure shall be analyzed，and re-detecting shall be made after taking relevant corrective measure（s）till the requirements are met.In the re-detecting process，the effectiveness of the corrective measure（s）shall be verified.

8.4.7　Records shall be kept for all the inspections，and pipeline detecting quality inspection report shall be compiled after the inspection.