The defect level shall be determined in structural defect evaluation of pipeline. The structural defect parameter F is the defect score after comparing the highest score and the average score of the pipeline defect, and the level of this parameter is consistent with the corresponding level of defect score. The structural defect level of the pipeline only reflects the damage condition with the pipeline structure, and the influence factors of external environment are not considered. The structural defect type of pipeline is the reference value for making comprehensive definition of local defect or whole defect in evaluation of the pipeline.
The determination of structural defect level of the pipeline shall conform to the provisions of Table 3.1.3-1. The structural defect type evaluation of the pipeline shall be determined according to Table 3.1.3-2.
Table 3.1.3-1 Contrast Table for Structural Defect Level Evaluation of Pipeline
| Level |
Defect Parameter F |
Description of Damage Condition |
| Ⅰ |
F≤1 |
No or slight defects, structural condition is basically unaffected, but there is the possibility of potential deterioration |
| Ⅱ |
1 |
Pipeline defects are significantly more than level 1, and there is a tendency of deterioration |
| Ⅲ |
3 |
Pipeline defects are serious, and structural condition is affected |
| Ⅳ |
F>6 |
There are major pipeline defects, serious damage or impending damage |
Table 3.1.3-2 Reference Table for Structural Defect Type Evaluation of Pipeline
| Defect Density SM |
<0.1 |
0.1~0.5 |
>0.5 |
| Structural defect type of pipeline |
Local defect |
Partial or whole defect |
Whole defect |
Calculation of pipeline rehabilitation index
The pipeline rehabilitation index is an index which indicates the urgency of pipeline rehabilitation and is confirmed after the structural defect level of pipeline is confirmed and the pipeline importance and environmental factors are considered. The pipeline needs to be rehabilitated as long as it has defects. However, if there are many pipelines needing to be rehabilitated, the rehabilitation ability is limited and the rehabilitation team has heavy tasks, the pipeline rehabilitation plan shall be worked out according to the severity of defects, degree of impact of defects on surroundings, and urgency of defects. The rehabilitation index is the basis for preparation of the rehabilitation plan, and it shall be calculated according to the following formula:
RI = 0.7×F + 0.1×K + 0.05×E + 0.15×T
Wherein: RI——Pipeline rehabilitation index;
K——Regional importance parameter, determined according to the provisions of Table 3.1.3-3;
E——Pipeline importance parameter, determined according to the provisions of Table 3.1.3-4;
T——Soil influence parameter, determined according to the provisions of Table 3.1.3-5.
The rehabilitation level shall be determined according to the rehabilitation index, and the higher the level is, the larger the urgency is. The pipeline rehabilitation level shall be determined according to the provisions of Table 3.1.3-6.
Table 3.1.3-3 Regional Importance Parameter K
| Region Category |
Value of K |
| Central business district and the area where there is Class-A civil building engineering nearby |
10 |
| The area where there are main traffic roads and there are Class-B civil building engineering nearby |
6 |
| The area where there are other roads and there are Class-C civil building engineering nearby |
3 |
| All other regions or F < 4 |
0 |
Table 3.1.3-4 Pipeline Importance Parameter E
| Pipe Diameter D |
Value of E |
| D＞1500mm |
10 |
| 1000mm＜D≤1500mm |
6 |
| 600mm≤D≤1000mm |
3 |
| D＜600mm or F＜4 |
0 |
Table 3.1.3-5 Soil Influence Parameter T
| Soil |
General soil layer or F=0 |
Silt layer |
Collapsible loess |
Expansive soil |
Muddy soil |
Red clay |
| Level IV |
Level III |
Level I, II |
Strong |
Medium |
Weak |
Sludge |
Mucky soil |
| Value of T |
0 |
10 |
10 |
8 |
6 |
10 |
8 |
6 |
10 |
8 |
8 |
Table 3.1.3-6 Pipeline Rehabilitation Level Division
| Level |
Rehabilitation Index RI |
Rehabilitation Suggestions and Instructions |
| Ⅰ |
RI≤1 |
The structural conditions are basically intact, no need to repair |
| Ⅱ |
1＜RI≤4 |
The structure will not be damaged in a short period of time, but there should be a plan to repair |
| Ⅲ |
4＜RI≤7 |
The structure may be damaged in a short period of time, and it should be repaired as soon as possible |
| Ⅳ |
RI＞7 |
The structure has been damaged or is about to be damaged, and it should be repaired immediately |
