Application of Rock Mass Classification Methods to the Klong Tha Dan Project Tunnels

Transcription

1 IJMMP Vol.3 No.1 Jun-June 12 pp: ISSN: International Science Press Application of Rock Mass Classification Methods to the Klong Tha Dan Project Tunnels J Ranasooriya *1, Myo Min Swe 2 & H R Nikraz 3 1 Department of Mines and Petroleum, Perth, Australia 2 Golden Tri star Co Ltd, Rangoon, Myanmar 3 Curtin University, Perth, Australia Abstract: Engineering geological mapping and classification of the rock mass intersected in five small diameter tunnels provided an opportunity to compare and correlate the two most widely used rock mass classification methods, Rock Mass Rating (RMR) and Tunnelling Quality Index (Q), under the project specific conditions. The tunnels were excavated through jointed volcanic rocks by conventional drilling and blasting techniques. The two methods were applied during construction and their support predictions were compared with each other and also with the actual support installed in the tunnels. The study showed that, in the five tunnels, more support was installed than those recommended by Q, whereas, RMR recommended support measures exceeded those installed. Linear regression analysis of the RMR and Q ratings of the five tunnels showed data scattering but a linear correlation similar to that commonly used for transforming ratings between the two systems was obtained. Key words: Rock mass rating, Q system, tunnel support, support pressures, comparison 1. INTRODUCTION As part of foundation treatment work of the Klong Tha Dan (KTD) water storage dam, five small diameter tunnels with a total length of 159 m were constructed. Four are drainage tunnels and the other is a grouting and drainage gallery. At the design stage of the project, support measures for the five tunnels were designed using the results of site investigations and taking into account the stability requirements specific to the project. During construction, for record purpose and communication between contractors and designers, the rock masses intersected in the five tunnels were classified according to the two most widely used rock mass classification methods, Rock Mass Rating (RMR) of Bieniawski (1989) and Tunnelling Quality Index (Q) of Barton et al. (1974). This provided an opportunity to determine the support requirements in accordance with the two methods and compare them with the actual support installed and also to correlate the ratings assigned. 2. PROJECT DESCRIPTION The KTD project located in Nakhon Nayok Province of Thailand is a major multipurpose water resources development scheme consisting of the largest roller compacted concrete (RCC) gravity dam in the world at that time. Constructed using an incredible 5.5 million cubic meters of concrete, it is 93 m high, approximately 2.7 km long, and has a maximum base width of 86 m. Together with a rock-earth saddle embankment dam, it creates a water storage reservoir of 224 million cubic meters at full supply level of 11 m RL. The main benefits of this project are irrigation, industrial water supply, flood control, fish harvesting and tourism. The project designed by Coyne & Bellier was constructed by a joint venture of four national and international construction firms (JV CCKV) for the Royal Irrigation Department of Thailand. Following its successful construction the project was formally commissioned in 5. The dam was founded on a solid rock surface with its lowest elevation at approximately 19 m RL. Strictly speaking the KTD RCC dam consists of two adjoining dams built between three hills: Hill A (right abutment), Hill B (middle) and Hill C (left abutment). The first dam connects Hills A 37

2 and B, and the second connects Hills B and C (Figure 1). A few meters below the crest level at 112 m RL the two dams join each other and become a single continuous structure making it the longest RCC dam in the world. The five tunnels constructed within the three hills are key components of the dam to control water losses through the foundation and also to ensure the stability of the dam by relieving uplift pressures. A summary of the tunnel details is provided in Table 1. Approximate locations of the tunnels are shown in Figure 1. Fig. 1 Long section of the dam showing the tunnel locations (upstream view) Table 1 Klong Tha Dan project tunnels Name Location Length (m) Shape W x H (m) Depth (m) Purpose TBR-D1 Hill A 227. D-shape 2.9 x Drainage TSB-D1 Hill B 388. D-shape 2.9 x Drainage TSB-D3 Hill B D-shape 2.9 x Drainage TSL-D2 Hill C 51. D-shape 2.9 x Drainage TSB-P Hill B 381. Horseshoe 4. x Grouting/drainage An extensive program of consolidation and curtain grouting was executed to improve the dam foundation conditions. The curtain grouting involving 6 m deep holes and part of the consolidation grouting were carried out from the grouting gallery (TSB-P). Immediately downstream of the grout curtain, which controls seepage through the dam foundation, a m deep drainage curtain was also established from the gallery. From the drainage tunnels, located 25 m downstream of TSB-P, a m nominal depth secondary drainage curtain was established. These are needed to control the hydraulic gradient and to reduce uplift pressure at the base of the dam. The long term stability of these tunnels and their efficient performance are therefore of paramount importance for the successful operation of the project. An evaluation of the seepage monitoring data undertaken by Mairaing et al. (7) confirmed that the seepage control system is in the condition as designed indicating that the five tunnels are functioning as per the design expectations. 2.1 Geology of the KTD Dam Site The KTD dam site mainly comprised undifferentiated Permo-Triassic volcanic rocks of the Khao Yai Volcanic Formation, which consists of rhyolite, andesite, rhyolitic and andesitic tuff and agglomerate and basalt (Phuntumat, 1997; Swe, 3). Within the site, the predominant geological discontinuities in the rocks are flow bands, joints and minor faults. No major regional-scale structures were present. The main rocks of Hill A are pyroclastic rocks which consist of agglomerate and tuff with minor occurrences of basalt and andesite at random. Hill C comprised lava rocks, namely rhyolite, 38

3 andesite and basalt. In Hill B (middle hill) the main rock type is rhyolite interrupted by basalt dykes. A series of laboratory tests conducted on core samples showed that the average uniaxial compressive strength (UCS) of rhyolite, andesite, agglomerate and tuff intact rock materials were 76, 134, 12 and 11 MPa, respectively. 2.2 Rock Mass Intersected in the Five Tunnels In the five tunnels rhyolite and tuff were the main rock types. Andesite, basalt and dacite were also present in small amounts usually as intrusions. The geological discontinuities intersected in the tunnels were flow bands, joints and minor faults. All five tunnels were excavated above the natural groundwater level and were dry during excavation. A summary of the rock types and the notable weakness zones intersected in the five tunnels is presented in Table 2. Table 2 Summary of the geological conditions of the five tunnels Tunnel Rock types Weakness zones/structures TBR-D1 Tuff 9%, basalt & adesite 1% Five minor fault/fractured zones at regular intervals TSB-D1 Rhyolite 9%, basalt 1% Twelve minor fault zones & three closely jointed zones TSB-D3 Rhyolite % Four minor fault zones & a closely jointed zone TSL-D2 Rhyolite %, basalt & dacite % Six minor faults, seven closely jointed zones with an average thickness of 2 m TSB-P Rhyolite 9%, basalt 1% Nine fault/fractured zones of less than 1 m thickness. A 3 m wide & two 5 m wide closely jointed zones. Since the rock mass is jointed the predominant form of ground response in the five tunnels was structurally controlled loosening. The tunnels were shallow and the in situ stresses were low and no stress related ground instability was observed. No water related effects were reported during construction as the natural groundwater level along the tunnel alignments was below the invert level. Structurally controlled failures occurred both in the crown and walls of the tunnels before the installation of support. After the completion of support installation no further instability occurred. 3. THE RMR AND Q ROCK MASS CLASSIFICATION METHODS The RMR and Q methods, which have gained wide acceptance in both mining and civil engineering applications, are based on six parameters considered to represent the behaviour of rock masses. Their primary aim is to divide a rock mass into classes of similar characteristics and to provide support recommendations for excavations created in the rock mass. The two methods are briefly outlined below. 3.1 The RMR Method The RMR method was first introduced by Bieniawski (1973) based on the experience gained from civil engineering project tunnels constructed primarily in South Africa. The method has undergone several revisions and its current version (Bieniawski, 1989) uses the following six parameters to rate a rock mass: Intact rock strength (IRS) Rock quality designation (RQD) Joint (discontinuity) spacing (JS) Joint surface condition (JC) Groundwater condition (GW) Rating adjustment (RA) for discontinuity orientation The six parameters are allocated different ranges of ratings and are rated based on observed or measured conditions in a rock mass. The sum of the ratings assigned to the six parameters is defined as the RMR value, which ranges from to. Guidelines on the selection of ratings and rock 39

4 support are provided in the references cited above. The support recommendations of the RMR system are for 1 m span horseshoe shaped tunnels with a vertical stress level of less than 25 MPa. The method can also be applied to smaller diameter tunnels as illustrated by Bieniawski (1989). 3.2 The Q Method The Q index was initially proposed by Barton et al. (1974). Developed primarily based on the data collected from civil engineering tunnels and caverns, the Q system also uses six parameters considered to represent the behaviour of rock masses: Rock quality designation (RQD) Joint (discontinuity) set number (Jn) Joint roughness number (Jr) Joint alteration number (Ja) Water reduction factor (Jw) Stress reduction factor (SRF) The system provides detailed guidelines on the selection of numerical ratings for the six parameters, covering a wide range of rock mass conditions that may be encountered in an excavation. Once the ratings are assigned to the six parameters the Q value, which range from.1 to, is calculated using the equation: Q = (RQD/Jn)(Jr/Ja)(Jw/SRF)...(1) The Q value is related to support requirements through an equivalent dimension, De, which is defined as: De = (Span, diameter or height)/esr... (2) where ESR, excavation support ratio, is a function of the purpose of the opening. A list of recommended ESR values is provided in the system. The Q system provides a support chart with Q value as its abscissa and De as its ordinate. By plotting the Q-De pair on the chart, the support requirements for excavations can be determined. 4. THE APPLICATION OF THE RMR AND Q METHODS TO THE CASE TUNNELS During excavation of the tunnels, the two rock mass classification methods were applied independently of each other and records of as-excavated rock mass conditions were prepared by site personnel. The records included a graphic log of engineering geology, a description of the rock mass, the minimum and maximum RMR and Q ratings for each m length of the five tunnels, support recommended by the two methods and a record of the support installed. The minimum and maximum RMR and Q ratings in each m tunnel length represent the worst and the best case ground conditions within that length. Tunnel construction details and the application of the two methods to the five tunnels are documented in the construction completion report (JV CCKV, 1) and the results of the application of the two methods are presented by Swe (3). In the five tunnels, the worst case and the best case RMR values ranged from 27 to 62 and 53 to 84, respectively, and the corresponding Q values ranged from.2 to 17 and 6 to 62, respectively. For comparison and correlation of the RMR and Q methods, the worst case and the best case ratings assigned to each m length of the tunnels are treated as two separate data sets, each representing a m length of a tunnel. Histograms of the percentages of rock mass falling into different RMR and Q classes under both the worst case and best case scenarios are shown in Figure 2. It is apparent from the histograms of RMR values presented in Figure 2 the difference between the worst case and the best case ground conditions is usually one RMR class. In other words, the RMR values increase (shift to the right in Figure 2) by only one rock mass class. In some instances the increase is less than one class as evident from the RMR values of TSB-D3 tunnel. In the case of the Q system, the difference between the worst and the best conditions is often more than one

5 rock mass class. This is an indication that compared to the Q system, the RMR system is less sensitive to the variations in the ground conditions intersected in the five tunnels. This is expected for two reasons. Firstly the RMR system has only five rock mass classes compared to the nine in the Q system. Secondly, the RMR value is derived by summing the ratings given to the six input parameters, while the Q value is the product of the three quotients (Equation 1) defined by the six input parameters. Hence any variation in the ratings assigned to the Q input parameters would result in a notable variation in the Q value. 6 (a) TBR-D1 RMR values RMR Values 6 (b) TBR-D1 Q values Q Values 6 (c) TSB-D1 RMR values RMR Value 6 (d) TSB-D1 Q values Q Value 6 (e) TSB-D3 RMR values RMR Value 6 (f) TSB-D3 Q values Q Values 6 (g) TSL-D2 RMR values RMR Value 6 (h) TSL-D2 Q values Q Value 6 (i) TSB-P RMR values RMR Value 6 (j) TSB-P Q values Q Value Fig. 2 Histograms Showing the s of Rock Mass Classes Under the Worst and Best Case Ground Conditions in Each Tunnel. 41

6 4.1 Comparison of RMR And Q Derived Support with Installed Support The RMR system introduced in 1973 has undergone several revisions and its current version is RMR 89 (Bieniawski, 1989). Its support recommendations remained largely unchanged. For nearly years the first version of the Q system (Q 74 ) introduced in 1974 remained unchanged until a revised version Q 94 (Grimstad and Barton, 1993; Barton and Grimstad, 1994) was proposed. In the revised version, the original classification parameters and the recommended ratings have not changed, except for those that have been made in the SRF term to accommodate slabbing and rock bursting cases in highly stressed ground. The changes in the SRF term of the Q system has no bearing on the KTD tunnels as they are shallow and the in situ stresses are low. The latest version (Q 94 ) also provided an updated support chart and reduced the number of support categories from the original 38 to nine, and simplified the support selection process. The support recommendations of Q 94 are somewhat different to those of Q 74, mainly because Q 94 relies on the use of fibre reinforcement for shotcrete instead of the welded wire mesh recommended previously. During construction of the five tunnels the RMR 89 and Q 74 versions were applied. Therefore, for the present study, the RMR 89 and Q 74 derived support measures were compared with the actual support installed. The support measures recommended by Q 94 are discussed separately. With the Q system, considering the need for regular access to the five tunnels, an ESR of 1.3 was used. Accordingly D e varies from 2.3 to 2.8 depending on the tunnel span. In order to compare the installed support with the RMR and Q support predictions, it was necessary to establish a set of support classes common to all three. In the KTD tunnels five predefined support classes denoted as Class I to V inclusive were used. The RMR method also has five support classes, denoted as Class I to V, and these can be directly compared with the support classes used. Q 74 has 38 support categories. Of which only four categories were applicable to the KTD tunnels with a Q values range of.2 to 62 and D e values of 2.3 to 2.8. They are the no support category and categories 21, 25 and 29. Since the support types and quantities of Categories 25 and 29 are essentially the same, these two categories were combined. The resulting three Q 74 support categories were then renamed as Class I (no support category), Class II (Category 21) and Class III (Categories 25 and 29). These can now be compared with the actual used and RMR predicted support classes. The support types in the relevant classes of Q 74 and RMR 89 and in the actual support classes used are given in Table 3. The percentages of rock mass falling into each relevant support class of Q and RMR and the actual support classes used are shown in Figure 3. Note that the percentages of Q and RMR support classes shown in Figure 3 are based on the worst case ratings assigned to the rock masses in the five tunnels. The best case support recommendations, which are unlikely to be used as the basis of permanent support design, were excluded from the comparison. As can be seen from Figure 3 and Table 3, the actual support measures installed were significantly more than the support requirements predicted by the Q system, whereas the RMR predicted support classes were comparable to the actual support classes used. However, it will be seen from Table 3 that the RMR recommended support, shotcrete and mesh in particular, are excessive compared to those of actual support Class III, which is the most commonly used in the five tunnels. This is partly due to the fact that the RMR support recommendations are for 1 m span tunnels and not necessarily for small span tunnels as in this project. In contrast the Q system has the flexibility to recommend support requirements virtually for any span. Nevertheless, as can be seen from Figure 3, for KTD tunnels, both RMR recommendations and the actual support installed far exceeded the Q system support recommendations. According to Q 74, 75% of the total tunnel length required no support, but in reality more than 9% of the total length was provided with support. This may be attributed to (a) the allocation of ratings for the Q input parameters were inaccurate, (b) the support designers and construction team were over conservative, or (c) the Q system under estimated the support requirements. These are discussed in the following sections. 42

7 Table 3 Support types in the five support classes of RMR, Q and the actual used Support class I II III IV V Q 74 system Bolts pattern None Systematic Systematic N/A N/A Shotcrete (mm) None mm (mr) Steel set spacing (m) None None None RMR system Bolts pattern None Spot/local Systematic Systematic Systematic Shotcrete (mm) None 5, if required 5- (mr) -15 (mr) 15- (mr) Steel set spacing (m) None None None Actual used Bolts pattern None Systematic Systematic Systematic Systematic Shotcrete (mm) None None 3 (mr) * 5 (mr) 5 (mr) Steel set spacing (m) None None None None mr = mesh reinforced, * occasional mesh, N/A not applicable RMR89 Q74 Actual of total tunnel length I II III IV V Support class Fig. 3 s of RMR 89 And Q 74 Recommended Support and Actual Support Classes Used in the Five Tunnels Accuracy of Q Ratings Allocation Since the RMR predicted support classes were generally in agreement with those used, it may be considered that the allocated RMR ratings represented the actual rock mass conditions in the five tunnels. In that case the accuracy of the allocated Q ratings may be cross checked by correlating the RMR and Q values assigned to the five tunnels. A plot of 17 RMR and Q data pairs representing the total length of the five tunnels is presented in Figure 4. By linear regression analysis of this data the following equation has been obtained: RMR = 6.3 ln Q (3) This equation is similar to the following equation derived by Bieniawski (1976, 1989) initially using 111 data pairs representing almost full range of RMR and Q values assigned to several different rock formations: RMR = 9 ln Q (4) 43

8 It can be seen from Figure 4 that the data used for deriving Equation 3 are widely scattered about the linear regression line. This is similar to the scattering of the 111 data pairs used in deriving Equation 4 (see Figure 1 and Figure 5.2 of Bieniawski 1976 and 1989, respectively). The main difference between the two equations is the gradient, which in Equation 3 is flatter than that in Equation 4. This difference is not uncommon. A literature review by Ranasooriya and Nikraz (9) showed that there are no less than 25 different RMR-Q correlations in the public domain and that scattering of the data used in deriving them is not uncommon. Further, they observed that different formulas can be obtained from different rock mass conditions. Nevertheless, the general similarity of the two equations and similar levels of data scattering indicates that the Q ratings allocation was reasonably accurate. 6 RMR y = 6.3Ln(x) R 2 = Q Fig. 4 Correlation for Klong Tha Dan project tunnels Conservativeness of The Support Designers and Tunnelling Crew As mentioned earlier the RMR predicted support classes were generally in agreement with the support classes used, but the actual support quantities installed (for instance shotcrete thickness) were less than those recommended. This may be an indication that support installed were not overconservative at least when compared to the RMR support recommendations. Further, the KTD project design required concrete lining of the grouting gallery. Since the purpose of the lining was not necessarily to deal with the as-excavated rock mass instability, it was not included in the present study for comparison with the RMR and Q derived support. The main purpose of the concrete lining was to ensure: (a) the stability of the tunnel during high pressure grouting, (b) an efficient grouting operation by preventing grout leakage into the tunnel, and (c) long term stability after the creation of the reservoir that generates a hydraulic head of more than m immediately above the tunnel excavated in dry rock mass conditions. These aspects are outside the scope of the two classification methods. Thus, for the present study only the primary support installed in the grouting gallery were considered. These support measures are unlikely to be overconservative as the gallery was to be fully lined soon after the completion of excavation. The main mode of rock mass instability during tunnel excavation was structurally controlled failure as noted in Section 2.2. An analysis of discontinuity orientation data collected during excavation showed potential for further rock wedge and block instability. In areas where potentially unstable rock blocks were relatively large due to wide spacing of discontinuities Class I support comprising pattern bolts were adequate. In closely jointed rock and fractured zones pattern bolts and shotcrete with wire mesh as necessary were used. These support measures far exceeded the Q 74 recommendations. According to the Q 94 support chart, a tunnel with a De of 2.3 to 2.8 would require no support if Q 2. Congruously, approximately 9% of the rock mass in the KTD tunnels requires no support. Only about 5% of the rock mass in the five tunnels requires Q 94 Category 5 support (systematic bolts 44

9 plus 5 to 9 mm of fibre reinforced shotcrete) and another 6% require Category 4 support (systematic bolts plus to mm of un-reinforced shotcrete). In effect Q 94 also recommended significantly less support than those installed in the five tunnels Comments on The Q Recommended Support From the foregoing it may be considered that Q 74 under estimated support requirements for the five KTD tunnels. This shortcoming in the Q system may be attributed to the lack of sufficient small diameter case records in the Q 74 database. A casual glance at the plus case studies used in developing the Q 74 support chart (Barton et al., 1974, 1977) would show that there weren t many small diameter tunnels in the database. The no-support boundary for small diameter (or small De) tunnels appeared to have extrapolated from other case studies. The revised version (Q 94 ) included 15 additional case studies, however, none of these represent small diameter tunnels. All of them have De values of 5 or more (see Figures 6 and 7 in Grimstad and Barton, 1993) indicating that they are medium to large diameter tunnels and caverns. In the Q 94 support chart, compared to the earlier version, the no-support boundary line is slightly flatter. The line appeared to have lifted up along the left margin of the chart. As a consequence small diameter tunnels with low De are more likely to fall into the no-support zone when plotted on the revised support chart. In other words, for small diameter tunnels the revised support chart is no better. According to the Q 94 support chart, the small span tunnels with a D e of around 2 do not require support if the Q values is greater than 2. While this may be true for the case studies included in the database used in developing the original Q system published in 1974, this has not been confirmed by any of the 15 additional case studies included in the updated database. The KTD project tunnels and a previous study by Ranasooriya and Nikraz (8a and 8b) which included a 3.5 m wide tunnel driven through meta-sedimentary rock showed that more support could be warranted for small diameter tunnels in jointed rock than those predicted by the Q system. In order to adequately cover support requirements of small diameter tunnels the no-support boundary should be modified. This cannot be done arbitrarily without sufficient case records in the database. In the mean time the users of the Q system should pay due attention to this limitation with respect to the small diameter tunnels. CONCLUSIONS By classifying the rock mass intersected during construction of five small diameter tunnels the two most widely used rock mass classification methods, RMR and Q, were applied to the project specific conditions and their support predictions were compared with the actual support installed. The RMR and Q rating values assigned to the five tunnels were correlated to cross check the general accuracy of the rating allocation. The formula obtained by linear regression analysis of the RMR and Q ratings of the five tunnels is similar to the commonly used correlation for transforming ratings between the two systems, but the two are not identical. The comparison showed that, in the five tunnels, more support was installed than those recommended by the Q classification method. The RMR system overestimated the support quantities but the predicted support types were comparable to those used. The study showed that more support could be warranted for small diameter tunnels in jointed rock than those predicted by the Q system. ACKNOWLEDGEMENTS The authors are grateful to the Klong Tha Dan project personnel, particularly of the Royal Irrigation Department of Thailand and the construction joint venture CCKV for providing the relevant data used in this study, which were initially compiled for the MSc research project of Myo Min Swe. The views expressed herein are those of the authors of the paper and not of their employers and the KTD project personnel. 45

10 REFERENCES [1] Barton, N. and Grimstad, E., The Q-system following years of application in NMT support selection, in Felsbau 12(6): pp [2] Barton, N., Lien, R. and Lunde, J., Engineering classification of rock masses for the design of rock support. Rock Mechanics. Vol. 6, pp [3] Barton, N., Lien, R. and Lunde, J., Estimation of support requirements for underground excavations. Design Methods in Rock mechanics. Proceedings, 16 th Rock Mechanics Symposium, University of Minnesota, ASCE 1977, pp [4] Bieniawski, Z.T., Engineering classification of jointed rock masses. Trans. South African Inst. Civil Eng. Vol. 15(12), pp [5] Bieniawski, Z.T., Rock mass classification in rock engineering. Proceedings, Symposium for Exploration for Rock engineering. Ed. Z.T. Bieniawski, AA Balkema, Rotterdam. pp [6] Bieniawski, Z.T., Engineering rock mass classifications, John Willey & Sons, New York, 251 p. [7] CCKV JV, 1. Final report on the completion of tunnel construction on Tha Dan Dam Project by JV CCKV (unpublished). [8] Grimstad, E. and Barton, N., Updating the Q-system for NMT, Proceedings, Intnl. Symposium on Sprayed Concrete, Norwegian Concrete Assoc, Oslo. pp [9] Mairaing, W., Thongthamchat, C. and Chaisiwamonghol, N., 7. Performance of seepage control system in the largest RCC dam in Thailand, published in: German Committee on Large Dams, ICOLD. [1] Ranasooriya, J. and Nikraz, H., 8a. Tetrahedral rock wedge stability under empirically derived support. Proceedings, 1 st Southern Hemisphere Intnl. Rock Mechanics Symposium, Sep 8, Perth, Vol. 1, pp [11] Ranasooriya, J. and Nikraz, H., 8b. An evaluation of rock mass classification methods used for tunnel support design. Proceedings, ARMS5, ISRM Intnl. Symposium 8, Tehran, Vol. 2, pp [12] Ranasooriya, J. and Nikraz, H., 9. Reliability of the linear relationship between Rock Mass Rating (RMR) and Tunnelling Quality Index (Q), Australian Geomechanics, Institution of Engineers Australia, June 9. [13] Swe, M. M., 3. Evaluation of support requirements in tunnel excavation at Klong Tha Dan Dam, Nakhon Nayok, Thailand, MSc Thesis, Asian Institute of Technology, Thailand. 46