Case study: application of NAT (New Abrasion Tester) for predicting TBM disc cutter wear and comparison with conventional methods

TBM 디스크 커터 마모 예측에 대한 NAT의 현장 적용 및 기존 방법과의 비교

Abstract

Wear prediction of TBM disc cutters is a very important issue during design as well as construction stages for hard rock TBMs as the cutter head intervention is directly related to the time and cost of tunneling. For that, some methods such as NTNU, CSM and Gehring models were used to predict disc cutter wear and intervention interval. There are however some problems to be addressed in these models in terms of accuracy and time for testing, so that a NAT (New Abrasion Tester) model has been developed in order to achieve simplicity and reliability together at the same time (Farrokh and Kim, 2018). On the basis, the proposed NAT model has been applied to ${\bigcirc}{\bigcirc}$ project in Korea. A comparative study was performed to compare with the conventional methods and as a result the NAT model showed a very good agreement with actual cutter life. The NAT model will be further applied to other projects to establish credibility.

암반용 TBM 공사에서 디스크 커터의 마모 예측은 설계 및 시공 단계에서 비용과 공기 측면에서 매우 중요한 요소이다. 디스크 커터 마모 예측에 널리 사용되고 있는 방법으로는 노르웨이 NTNU 모델, CSM 모델과 Gehring 모델이 있지만, 시험의 정확도와 소요 시간의 측면에서 개선의 여지가 있었다. 이를 반영하여 NAT (New Abrasion Tester) 모델을 개발하였다(Farrokh and Kim, 2018). 제안된 NAT를 국내 ${\bigcirc}{\bigcirc}$현장에 적용하였고, 기존의 방법과 비교 검토를 수행하였다. 분석 결과 ${\bigcirc}{\bigcirc}$현장의 경우 기존 방법에 비해 NAT의 예측 결과가 커터 교체 현장 실측 데이터와 잘 맞는 것으로 나타났다. NAT 모델을 향후 더 많은 현장에 적용하여 모델의 신뢰도를 높일 예정이다.

Fig. 1. NTNU test

Fig. 2. Cerchar test

Fig. 3. NAT (New Abrasion Tester) and test method

Fig. 4. NAT rock sample and disc

Fig. 5. Correlation between DWI and SCWL (Farrokh and Kim, 2018)

Fig. 6. Calculation of SCWL for NAT (Farrokh and Kim, 2018)

Fig. 7. Geological map of ○○ site

Fig. 8. Photograph of TBM & Rock surface in front of cutter head

Fig. 9. Cutterhead layout drawing

Fig. 10. Record for cutter intervention

Fig. 11. NAT and rock sample

Fig. 12. Cerchar & NTNU tests

Table 1. Prediction models for disc cutter wear (Kim et al., 2017)

Table 2. Disc cutter wear schemes

Table 3. Disc cutter wear weigh loss

Table 4. NAT Test results

Table 5. Comparison between site record and test results

Table 6. Disc cutter wear weigh loss