5 Scanning
5.1 Assumptions for the scanning analysis
Scanning performed in Bjørnegård tunnel can be considered as a high technology process.
Precise scans give very accurate 3D model of the excavated tunnel which can be used for geometrical and visual estimation of the scanned tunnel surface.
Figure 5.1 3D model from scanning
In this thesis calculation and tunnel contour analyses were executed for cross sections for every 0.5 m. Form of the results outcome is shown in the Figure 5.2
50
( i ) Overblasted area and contour length ( j ) Overbreak
Figure 5.2 Scanning outcome
To ensure uniform scanning results, a line 1 m above the center of the bottom of the tunnel profile was added. Only data above this line was considered for the analyses. This was caused by the fact that even though scanning was performed after removal of the blasted rock, in some places there were remains of the material left on the sides. Since the scanner is measuring distances to visible surfaces and mentioned above rock was not part of the tunnel contour, scanning data from the bottom of the profile could give incorrect results.
Some of the scanned cross sections had to be rejected from the calculation because data was damaged. This was due to the fact that the scanner was placed a few meters in front of the tunnel face under an already applied rock support. Scans of the contour surface after blasting had to be separated manually from the scans of the rest of the tunnel. Since the line of the shotcrete applied in the previous rounds is not regular, sometimes results from the beginning of the round were not complete. Also some scans form the end of the round had to be rejected by the reason of not regular tunnel face.
51 Figure 5.3 Example of rejected profile
Number of scanned cross sections with the results acceptable for calculation varies for most of the rounds as shown in Table 5.1 and Table 5.2
Non-electric detonators
Round 1320 1326 1331 1337 1342 1347 1410
Q-value 8,8 14 20 16 10 6,2 2,2
Number of profiles 10 11 11 11 7 8 10
Table 5.1 Number of scanned profiles – non-electric detonatros Electronic detonators
Round 1441 1447 1452 1457 1462
Q-value 3,1 3,1 3,1 2,8 2,5
Number of profiles 11 9 9 10 7
Table 5.2 Number of scanned profiles – electronic detonators
Scanning of the tunnel for electronic detonators rounds was performed both before and after scaling, but in this thesis only results from scanning after scaling were used for unification of the results.
Separation of the profiles from scanning results into rounds sets was done based on the information from diaries of Statens vegvesen quality engineers.
52 5.2 CONTOUR LENGTH
5.2.1 RESULTS FROM NON-ELECTRIC DETONATORS ROUNDS
Contour length results analyzed in this thesis are the average of the results from each blasting round. The analysis was done separately for non-electric and electronic detonators rounds.
Table 5.3 presents results from contour length analysis for non-electric detonators rounds.
The length of the theoretical tunnel contour calculated above the additional line was 20.74 m.
Average length of all analyzed cross sections is 23.60 m, what gives average 2.86 m longer contour. The ratio of actual contour length to planned contour length (RCL) for all blasting rounds is equal to 1.14, meaning a 14% difference in contours lengths. The round with the smallest difference between both contours was the first scanned round, 1320, with RCL equal to 1.09 and average difference of 1.92 m. Round with the highest ratio of the lengths is the last round of non-electric rounds with RCL found to be 1.20. That gives 20% difference
Table 5.3 Contour length – non-electric detonators
53
Figure 5.4 Graphical presentation of contour length – non-electric detonators
Figure 5.5 Average RCL – non-electric detonators
5.2.2 RESULTS FROM ELECTRONIC DETONATORS ROUNDS
Table 5.4 presents results from electronic detonators rounds. The average contour length for all five rounds was 24.19 m, which gives a 3.45 m difference from the theoretical contour length. Average RCL for the test stretch is 1.17. All rounds with electronic detonators had quite similar average contour length which varied from 23.66 m (RCL 1.14) in round 1462 to 2.43 m (RCL 1.18) in round 1457.
20,74 20,74 20,74 20,74 20,74 20,74 20,74
1,92 2,02 2,57 3,01 3,16 3,47 4,19
22,66 22,76 23,31 23,74 23,89 24,20 24,92
0
1320 1326 1331 1337 1342 1347 1410
Round
1320 1326 1331 1337 1342 1347 1410
Round
Average RCL
54
Table 5.4 Contour length – electronic detonators
Figure 5.6 Graphical presentation of contour length – electronic detonators
Figure 5.7 Average RCL – electronic detonators
20,74 20,74 20,74 20,74 20,74
55 5.2.3 ANALYSIS AND DISCUSSION
Compilation of the results from the contour length calculation from non-electric and electronic detonators are shown in Table 5.5. It was found that even though there was an assumption that test rounds should be characterized by the better quality of the contour, results of the contour length calculations were worse for the electronic detonators rounds. In general, the smaller the difference between the theoretical contour length and the actually blasted contour length, the better. Likewise, RCL value for the ideal case is equal to 1.0 and as its value becomes greater, it means the bigger difference of the contour.
Average contour
Table 5.5 Compilation of contour length results
As it is shown in the Table 5.5, the average difference between contour lengths from test rounds was 59 cm bigger than in non-electric detonators rounds. That implies the greater value of the RCL, which average value for non-electric detonators was equal to 1.14 and for electronic – 1.17. It was also found that in non-electric detonators rounds, both the highest and the lowest RCL value were registered. The difference between RCL values achieved in non-electric detonators varied from 1.09 to 1.20, corresponding to the length difference of 9%
to 20%. In the test rounds, values differ from 1.14 to 1.18 (14% to 18%). This distribution of the RCL shows that electronic detonator rounds have more uniform distribution of the results.
Based on scanning results, it can be assumed that in terms of contour length, the achieved contour was better for non-electric detonators rounds than for the test rounds.
56 Figure 5.8 RCL results compilation
Figure 5.9 Graphical presentation of contour length
5.3 BLASTED AREA
5.3.1 RESULTS FROM NON-ELECTRIC DETONATORS ROUNDS
Results from blasted area calculation for non-electric detonators rounds are presented in the Table 5.6. The theoretical blasted area (above additional line 1 m above the bottom of the contour) was equal to 66.53 m2. The average blasted area for all seven rounds was equal to 76.33 m2, giving 9.80 m2 of average overblast area. The ratio of the actually blasted to
1320 1326 1331 1337 1342 1347 1410 1442 1447 1452 1457 1462 Round
Average RCL
20,74 20,74 20,74 20,74 20,74 20,74 20,74 20,74 20,74 20,74 20,74 20,74 1,92 2,02 2,57 3,01 3,16 3,47 4,19 3,63 3,27 3,54 3,69 2,92 22,66 22,76 23,31 23,74 23,89 24,20 24,92 24,37 24,01 24,28 24,43 23,66
0
1320 1326 1331 1337 1342 1347 1410 1442 1447 1452 1457 1462 Round
Actual contour length [m]
57
planned area (RBA) for all non-electric detonators rounds was 1.15, corresponding to a 15%
difference. There were two rounds, 1320 and 1326, with similarly small overblast area equal to 6.53 m2 and 6.63 m2 respectively. For both rounds, difference between planed and achieved area was around 10%. Round with the biggest blasted area was round 1342 with 79.92 m2 and 20 % difference between planned area and actually blasted one.
Round Planned
Table 5.6 Blasted area – non-electric detonators
Figure 5.10 Graphical presentation of blasted area – non-electric detonators
66,53 66,53 66,53 66,53 66,53 66,53 66,53
6,53 6,63 9,13 10,94 13,40 12,06 11,70
73,07 73,19 75,70 77,47 79,92 78,56 78,21
0
1320 1326 1331 1337 1342 1347 1410
Round
Blasted area [m2]
58 Figure 5.11 Ratio of blasted area – non-electric detonators 5.3.2 RESULTS FROM ELECTRONIC DETONATORS ROUNDS
The average blasted area for the electronic detonators rounds was 76.88 m2. That result gives average 10.35 m2 of overblast area and RBA equal to 1.16. For each rounds average percentage difference of the areas varies from 13 to 18%. Round with the smallest overblast area was round 1452 with 8.83 m2 and 75.35 m2 of actually blasted area. Round with the largest – 1442, had 12.07 m2 of overblast area and 78.64 m2 of actually blasted area.
Round Planned
Table 5.7 Blasted area – electronic detonators 1,10 1,10
1320 1326 1331 1337 1342 1347 1410
Round
Ratio of blasted area Non-electric detonators
59
Figure 5.12 Graphical presentation of blasted area – electronic detonators
Figure 5.13 Ratio of blasted area – electronic detonators 5.3.3 ANALYSIS AND DISCUSSION
The analysis of the overblasted area is similar to the analysis of the contour length. In general, the smaller the overblasted area, the better. Additionally, the assumption for the ideal case, with RBA equal to 1.0, is analogic to the RCL estimation. A compilation of the results from blasted area calculation is presented in Table 5.8.
Average overblast
Table 5.8 Compilation of blasted area results
66,53 66,53 66,53 66,53 66,53
60
Results of the blasted area averages for non-electric and electronic detonators are relatively similar to each other. Average overbreak is found to be around 10 m2 for both sets of data, what is corresponding to RBA equal to 1.15-1.16 (15-16% of the difference from the theoretical area). RBA value for all 12 analyzed rounds are distributed between 1.10 and 1.20, and both, the highest and the lowest values are in the non-electric detonators data set. RCL just for test rounds, varies from 1.13 to 1.18. Based on the achieved results, no big improvement of the blasted area was observed.
Figure 5.14 RBA results compilation
Figure 5.15 Graphical presentation of blasted area
1,10 1,10
1320 1326 1331 1337 1342 1347 1410 1442 1447 1452 1457 1462 Round
Ratio of blasted areas
66,53 66,53 66,53 66,53 66,53 66,53 66,53 66,53 66,53 66,53 66,53 66,53 6,53 6,63 9,13 10,94 13,40 12,06 11,70 12,07 9,89 8,83 9,82 10,94 73,07 73,19 75,70 77,47 79,92 78,56 78,21 78,64 76,44 75,35 76,33 77,47
0
1320 1326 1331 1337 1342 1347 1410 1442 1447 1452 1457 1462 Round
Blasted area [m2]
61 5.4 OVERBREAK
Overbreak in this thesis is defined as the distance from planed contour line to the actually blasted contour line. For each round, the number of cross sections taken under consideration for the calculation are specified in Table 5.9. Only distances above the additional line were used for analysis of the overbreak.
Round
Table 5.9 Number of scanned profiles
5.4.1 RESULTS FROM NON-ELECTRIC DETONATORS ROUNDS
Figure 5.16 presents a graphical interpretation of average deviation of the overbreak.
Round Min [mm] Max [mm] Average deviation per
Table 5.10 Overbreak results – non-electric detonators
62
Figure 5.16 Graphical presentation of overbreak – non-electric detonators
The biggest overbreak was calculated for round 1342 where the highest value in profile 1347 was equal to 689 mm. In the same round, the average deviation per round had also the highest result with 615 mm. The first round of the scanning was characterized by the smallest average overbreak equal to 308 mm, but the smallest overbreak per profile was observed in round 1326 with 232 mm. Average overbreak for all seven rounds was 453 mm.
5.4.2 RESULTS FROM ELECTRONIC DETONATORS ROUNDS
For five electronic detonators rounds, the average value from all profiles was equal to 481 mm. The biggest average deviation per round was in round 1442 and it was 562 mm. In this round there was also profile with the highest calculated value from scanning equal to 656 mm. Round with the lowest average deviation was round 1452, but profile with the lowest value was 1463.5 in round 1462 with 338 mm of overbreak. Graphical interpretation and table with results are presented below.
Round Min [mm] Max [mm] Average deviation per
Table 5.11 Overbreak results – electronic detonators
0
1320,5 1321,5 1322,5 1323,5 1324,5 1325,5 1326,5 1327,5 1328,5 1329,5 1330,5 1331,5 1332,5 1333,5 1334,5 1335,5 1336,5 1337,5 1338,5 1339,5 1340,5 1341,5 1342,5 1343,5 1344,5 1346,0 1347,0 1348,0 1349,0 1410,5 1411,5 1412,5 1413,5 1414,5
Profile number
Average overbreak [mm]
63
Figure 5.17 Graphical presentation of overbreak – electronic detonators 5.4.3 ANALYSIS AND DISCUSSION
Results from the overbreak calculation show that average overbreak for non-electric detonators was lower than for electronic detonators rounds. For rounds with normally used detonators, the average overbreak was 45.3 cm, what was 2.8 cm smaller than the value of the overbreak for test rounds.
Average overbreak [mm]
NO-TEST 453
TEST 481
Table 5.12 Compilation of overbreak results
No special requirements for overbreak were stipulated for the electronic detonators test, so according to Stanens vegvesen Road Tunnel Strategy Study (2010), the boundary line of the overbreak can be calculated by the equation:
𝐷 = 0,07 ∙ 𝐴 where:
D – distance between the theoretical excavation line and the boundary line A – Theoretical excavated surface area
For the 78 m2 theoretical area of the whole profile, D value is equal to 61.8 cm. None of the overbreak averages per round exceed this value, but in some averages of the profiles, the limit distance was surpassed. The overbreak limit distance was achieved in rounds 1337 (62.2 cm),
0
1441,500 1442,000 1442,500 1443,000 1443,500 1444,000 1444,500 1445,000 1445,500 1446,000 1446,500 1447,000 1447,500 1448,000 1448,500 1449,000 1449,500 1450,000 1450,500 1451,000 1452,000 1452,500 1453,000 1453,500 1454,000 1454,500 1455,000 1455,500 1456,000 1457,000 1457,500 1458,000 1458,500 1459,000 1459,500 1460,000 1460,500 1461,000 1461,500 1463,500 1464,000 1464,500 1465,000 1465,500 1466,000 1466,500
Profile number
Average overbreak [mm]
64
1342 (68.9 cm), 1347 (66.1 cm), 1410 (67.4 cm) from non-electric detonators rounds and in rounds 1442 (62.9 cm) and 1462 (65.6 cm) from test stretch.
Average overbreak per round for non-electric detonators varies from 30.8 cm to 61.5 cm, which gives around a 30 cm difference between minimum and maximum value. For electronic detonators the variation of the results was between 41.3 and 56.2 cm with a 15 cm difference between extreme values.
The assumption was that use of the electronic detonators would decrease the overbreak dimension, but instead of reduction, small increase of the overbreak average was observed.
Although, test rounds comparing to non-electric detonators rounds are characterized with the more uniform distribution of the results. The difference between extreme values were twice smaller for electronic detonators. The difference between overbreak averages for both sets of data is slight, therefore it can be stated that the quality of the contour in terms of overbreak is similar for all rounds.
5.5 TUNNEL QUALITY INDEX
Tunnel Quality Index, TCI, proposed by Kim (2009) was used in this thesis for evaluation of the contour quality of a tunnel. TCI can be calculated for the one round, TCIR, or for the entire tunnel (or more than 5 rounds) - TCIT. Formula for TCI estimation proposed by Kim (2009) was slightly changed for the need of this thesis and it is determined by equation below.
The difference is that the ratio of contour length element used in the contour length element of the formula. Because data from scanning provided very accurate contour lengths it was possible to evaluate the ratio using actual contour length and planned contour length, so there was no need for empirical estimation of the ratio like it was proposed by Kim.
𝑇𝐶𝐼7 = 300 𝑉A - Longitudinal overbreak variation (cm)
𝑅𝐶𝐿 - Ratio of actual contour length to planned contour length
65
5.5.1 RESULTS FROM NON-ELECTRIC DETONATORS ROUNDS
Results from Tunnel Quality Indexes calculation are presented below. TCIR for non-electric detonators was distributed between 51.6 and 63. Round 1320 had the highest TCIR value equal to 63. Round with the lowest TCIR was round 1342 with 51.6. Calculated for all seven rounds, TCIT, which included also longitudinal overbreak variation element, was equal to 54.1.
Round Average contour
length per round [m] Average RCL Average
overbreak [cm] TCIR
Table 5.13 TCI results – non-electric detonators
Figure 5.18 TCIR results – non-electric
detonators Figure 5.19 TCIT result – non-electric detonators
5.5.2 RESULTS FROM ELECTRONIC DETONATORS ROUNDS
Table 5.14 shows the results from TCIR calculation. It was found that TCIR for electronic detonators rounds was distributed between 52.2 and 56.3. The most favorable contour quality
63,0 62,6
1320 1326 1331 1337 1342 1347 1410 Round
66
had round 1452. Round with the lowest TCIR equal to 52.2 was round 1442. The results of the TCIL calculation showed that for all test rounds, taking into account the longitudinal overbreak variation element, contour quality was equal to 53.6.
Round
Average contour length
per round [m]
Average RCL Average Overbreak [cm] TCIR
1442 24.37 1.17 56.2 52.2
Table 5.14 TCI results – electronic detonators
Figure 5.20 TCIR results – electronic detonators Figure 5.21 TCIT result – electronic detonators
5.5.3 ANALYSIS AND DISCUSSION
Compilation of the results from TCI calculation is presented in Table 5.15, and Figures 5.22 and 5.23 below.
67
Table 5.15 Compilation of TCI results
Figure 5.22 Compilation of TCIT results
Figure 5.23 Compilation of TCIR results 54,1
57,8 54,7 51,6 52,7 51,9 52,2 55,5 56,3 54,9 54,8
0,0
1320 1326 1331 1337 1342 1347 1410 1441 1447 1452 1457 1462 Round
TCIR
68
In general, higher TCI values means better contour quality. Kim (2009) in his thesis estimated the extreme values for TCIT: 29.8 for extremely bad case (overbreak – 155 cm, RCL – 1.34, longitudinal overbreak variation – 53 cm) and 81.5 for an ideal case (1 cm, 1.01, 1 cm – respectively). For normal cases, he evaluated the interval of TCIT values from 38.6 to 61.6.
For TCIR there are none special boundaries estimated.
TCIT results from Bjørnegård tunnel were similar for both type of detonators rounds. In non-electric detonators rounds, TCIT of 54.1 was calculated. A slightly smaller value was achieved for electronic detonator rounds, where TCIT was equal to 53.6. TCIR in all calculated rounds varied from 51.6 to 63.0. Both extreme results were achieved in non-electric detonators rounds. Results from test rounds were in the range of 52.2 to 56.3.
TCIT of 54 achieved for both detonators rounds was in the interval described by Kim for normal cases. Calculated value is more or less in the middle of the given interval and since there is no partition of the TCIT into quality groups, the quality of 54 in this thesis will be estimated as average.
5.6 SUMMARY OF SCANNING
In the scanning chapter, data from laser scanning of the tunnel was analyzed. 103 profile scans were used for the analysis: 68 from non-electric detonators and 35 from electronic detonators rounds. The goal was to analyze achieved contour and evaluate the influence of change of the ignition system on the quality. The assumption was that the use of electronic detonators could have a positive impact on contour quality.
Scanning was performed with a high technology scanner, which provided very accurate 3D model of the tunnel surface and information about the geometry of the tunnel. Types of data from the scanning used in this thesis were following:
- Theoretical contour length, - Actual contour length, - Theoretical blasted area, - Overblast area,
- Distances from the theoretical contour to actual contour.
Scanning was performed after removal of loose material (scaling) and scanner while measurements was placed few meres in front of tunnel face. Results from scanning were given for every 0.5 m of the scanned rounds, but in some cases data was damaged and those
69
profiles were rejected from the calculation. Calculations were done for the cross sections above additional line 1m above the bottom of the contour.
Analysis was based on evaluation of following values:
- RCL – ratio of actual contour length to planned contour length, - RBA – ratio of actual blasted area to planned blasting area,
- Overbreak – the average of the distances from the theoretical contour to actual contour,
- TCI – Tunnel Contour Quality Index.
Summary of the results from this section is presented in the Table 5.16 below:
Average RCL Average RBA Average overbreak [mm] TCIT
NO-TEST 1.14 1.15 453 54.1
TEST 1.17 1.16 481 53.6
Table 5.16 Compilation of scanning results
Calculation of the mentioned above values, showed that there was no big improvement of the result in the rounds with electronic detonators. Furthermore, analysis of the scans indicated a slight deterioration of achieved results from the test stretch. However, the differences between results from both sets of data are rather similar with small deviations. Based on the outcomes from scanning results calculation, it can be assumed that the quality of the tunnel contour was very similar for non-electric and electronic detonators rounds.
In terms of overbreak calculation, according to Stanens vegvesen Road Tunnel Strategy Study, the limit value of the overbreak for the 78 m2 tunnel cross section is equal to 61.8 cm.
None of the overbreak averages exceeded this value, though in some profiles, the limit distance was surpassed. The overbreak limit distance was achieved in rounds 1337 (62.2 cm), 1342 (68.9 cm), 1347 (66.1 cm), 1410 (67.4 cm) from non-electric detonators rounds and in rounds 1442 (62.9 cm) and 1462 (65.6 cm) from test stretch.
Considering guidelines for TCIT suggested by Kim (2009) it can be stated that achieved contour quality was average. TCIT of 54 is more or less in the middle of Kim’s interval for normal cases. The average TCIT is slightly different for non-electric and electronic detonators rounds and it is higher for the first set of data. Both averages for RCL, RBA and overbreak results are comparable for test rounds and for rounds before test.
70
Two last rounds of electronic detonator tests increased the drilling hole diameter from 48 mm to 60 mm. The change in the hole dimension did not influence the achieved results in a significant way.
71
6 C
ONCLUSIONS AND RECOMMENDATIONS6.1 CONCLUSIONS
The main idea of the thesis was to analyze the excavation of the E16 Sandvika-Wøyen Bjørnegård tunnel with special focus on the achieved contour quality and influence of applied initiation system. The analysis in the thesis is divided in the two major parts:
- Analysis of the drilling results - Analysis of the scanning results
Discussion and analysis are included in conclusion section.
Drilling analysis was based on the MWD data from the drilling jumbo which was divided into two groups:
- Local coordinates – used for the estimation of the spacing and length of the contour holes
- Global coordinates – used for the calculation of the start and end position of the holes
- Global coordinates – used for the calculation of the start and end position of the holes