ROCK CUTTING FORCE ESTIMATION IN TUNNELING WITH TBM

The performance of TBM affects the execution cost and completion time of the rock excavation project. Therefore, it is vital to correctly predict the performance of TBM. Despite the large amount of research about TBM performance and estimation of its parameters, there is still a gap. Predicting cutting force remains a complex task due to the variability in rock conditions and properties, the diversity of TBM types, and the need to consider all relevant parameters and properties together. Therefore, it is necessary to analyze data using regression models based on statistical analysis. This thesis aims to address the performance prediction problem and improve the performance prediction model by gaining a better understanding of the interaction between rock and cutting force. To achieve the goal of this study, simple linear, multilinear and nonlinear regression analysis based on statistical analysis approaches were employed to develop a series of TBM performance model. A comprehensive database of TBM performance compiled from 3 tunnelling projects of Iran (Zagros, Ghomrood and Karaj), was established and used for the development of the model. The results of the study showed the influence of different rock parameters on the cutting force. Also, the quality of the rock has a significant impact on the cutting force. The results indicated that non-linear equations are more robust than linear models because linear relationships are less realistic under such volatile and unpredictable conditions. Compared to previous research, the current model, which utilizes intact rock properties and rock mass properties, has demonstrated favorable outcomes. This implies that the equations are dependable in predicting TBM (Tunnel Boring Machine) performance and can be utilized in situations where machine parameters are lacking. The conclusion drawn was that intact rock properties serve as the primary input parameters for predicting TBM performance. However, relying solely on intact rock properties may be insufficient, as in cases of fragmented rock, they may not adequately reflect the strength of the rock mass. It is also important to note that using the prediction formula without machine parameters can lead to inaccurate results, since machine parameters are also volatile in different conditions and affect the performance of TBM in a complex way. Method can be used for more extensive analysis, but limitations such as unrealistic values when imputing data must be taken into accoun

Evaluation of excavated surface irregularities and hardness of mechanical excavations and their relationship with excavator performance

This research involved lab and numerical excavation of a clastic sedimentary rock (Roubidoux Sandstone) using a long-bladed disc cutter in a Linear Rock Cutting Machine (LCM) with the aim of establishing relationships between the cutting parameters, excavated surface parameters (underbreaks, overbreaks and hardness), and performance parameters (specific energy and cutting rate). Three-dimensional cutting forces were recorded during the linear cutting. A structured laser imaging system was used to image the excavated surfaces for the estimation of the irregularities (ridge volumes (RV) and overbreak volumes (OV)). The excavated surface hardness was measured using the N-type Schmidt hammer. The numerical simulation was conducted in Itasca’s Particle Flow Code 3D (PFC3D). It involved model calibration, a study of the effects of the cutting geometry and cutter scale on the cutting forces, validation of the models using the lab cutting data, and a study of the effects of cutter size on the cutting forces. The results showed that the RV increased with increasing spacing-penetration (s-p) ratio for s-p ratios at which relieved cutting was achieved. However, the RV decreased with increasing s-p ratio under unrelieved cutting. The OV had a negative linear correlation with the s-p ratio under relieved cutting. In unrelieved cutting, the OV was independent of the s-p ratios. These findings can be used to determine the s-p ratio at which relieved cutting is first achieved. The specific energy decreased linearly with increasing surface hardness. The hardness was used together with the s-p ratio to develop a function for estimating SE. The numerical models yielded logarithmic functions for scaling forces from linear rock cutting simulations in PFC3D --Abstract, page iii

Tunnel boring machine performance prediction in tropically weathered granite through empirical and computational methods

Many works highlight the use of effective parameters in Tunnel Boring Machine (TBM) performance predictive models. However, there is a lack of study considering the effects of tropically weathered rock mass in these models. This research aims to develop several models for predicting Penetration Rate (PR) and Advance Rate (AR) of TBMs in fresh, slightly weathered and moderately weathered zones in granite. To achieve these objectives, an extensive study on 12,649 m of the Pahang- Selangor Raw Water Transfer (PSRWT) tunnel in Malaysia was carried out. The most influential parameters on TBM performance in terms of rock (mass and material) properties and machine specifications were investigated. A database consisting the tunnel length of 5,443 m, 5,530 m and 1,676 m representing fresh, slightly weathered and moderately weathered zones, respectively was analysed. Based on field mapping and laboratory study, a considerable difference of rock mass and material characteristics has been observed. In order to demonstrate the need for developing new models for prediction of TBM performance, two empirical models namely QTBM and Rock Mass Excavatability (RME) were analysed. It was found that empirical models could not predict TBM performance of various weathering zones satisfactorily. Then, multiple regression (i.e. linear and non-linear) analyses were applied to develop new equations for estimating PR and AR. The performance capacity of the multiple regression models could be increased in the mentioned weathering states with overall coefficient of determination (R2) of 0.6. Furthermore, two hybrid intelligent systems (i.e. combination of artificial neural network with particle swarm optimisation and imperialism competitive algorithm) were developed as new techniques in field of TBM performance. By incorporating weathering state as input parameter in hybrid intelligent systems, performance capacity of these models can be significantly improved (R2 = 0.9). With a newly-proposed systems, the results demonstrate superiority of these models in predicting TBM performance in tropically weathered granite compared to other existing and proposed techniques

Universal physics-based rate of penetration prediction model for rotary drilling

The drilling process is one of the most important and expensive aspects of the oil and gas industry. Drilling is required during mining for different ore production processes such as blasting and large drilling operations. Overall, it contributes significantly to the total cost of mining. As a result, an accurate prediction of the rate of penetration (ROP) is crucial for drilling performance optimization and contributes directly to reducing drilling costs. Knowledge of drilling performance is a powerful tool to aid in the development of a consistent drilling plan as well as to anticipate issues that may arise during drilling operations. Several approaches, with varying degrees of complexity and accuracy, have been tested to predict drilling performance, but all have shown several limitation to predict the complete drilling performance curve including locate the founder point. This limitation can be extended to their capacity of covering different drilling scenarios with high accuracy. In this thesis (manuscript style) a review of the history of drilling performance prediction is conducted with emphasis on the rotary drilling of small and large diameters. The approaches are grouped into two categories: physics-based models and data-driven models. Due to the low complexity of the physics-based models and the scarcity of drilling performance prediction research that reports the founder point location, a novel physics-based ROP prediction model for rotary drilling that includes the founder point location is presented. This model presents high accuracy to predict the drilling performance for fixed cutter drill bit, roller-cone drill bit, and large diameter drilling operations. The behaviors of the new model constants (drillability coefficient and drillability constant term) are discussed when analyzed in relation to the unconfined compressive strength (UCS), bit diameter, and rotary speed. Additionally, a new experimental setup approach was developed based on the circular movement of the full-scale disc cutter that are normally used in raise boring and tunnel boring machines. This setup will permit to simulate the large diameter drilling operations in laboratory scale aiming the understanding of the fragmentation process and application of optimization to this scenario

Discrete Element Modelling (DEM) For Earthmoving Equipment Design and Analysis: Opportunities and Challenges

Simulation of granular materials (soil, rocks) interaction with earthmoving machines provides opportunities to accelerate new equipment design and improve efficiency of earthmoving machine performances. Discrete Element Modelling (DEM) has a strong potential to model soil and rocks bulk behavior in response to forces applied through interaction with machinery. Numerical representation of granular materials and methodology to validate and verify constitutive micro-mechanical models in DEM will be presented. In addition, how DEM codes can be integrated to CAE tools such as multibody dynamics will also be discussed. A case study of tillage bar-soil interaction was modeled in EDEM to predict tillage draft force and soil failure zone in front of tool moving at 2.68-m/sec and depth of 102-mm. The draft force and soil failure zone was predicted at 10% and 20% error from laboratory measured data

Empirical correlations between rock cutting parameters and excavated rock surface rebound hardness

In field excavation, cutting tools operate on rock surfaces damaged from previous tool pass, yet, average intact rock properties are often used in field project estimations. This can result in overestimation of excavation time and cost. The ability to accurately correlate the damaged rock properties to the excavation parameters means more reliable estimates of project completion time and costs, and hence improved the application of mechanical excavation technology to a wider range of civil and mining industries. The purpose of this research was to better understand the relationship between rock cutting parameters and the excavated rock surface hardness during mechanical excavation. To do this, Roubidoux sandstone was subjected to linear cutting experiments using a radial drag pick at different cut spacing to depth of cut (s/d) ratios and the resultant forces and chips were analyzed. The rebound hardness of the excavated rock surface was subsequently measured using a rock-type Schmidt hammer. Results and subsequent analysis indicated that the wide variability of Roubidoux sandstone coupled with the complex process of rock cutting prevented a clear determination of the relationship between the cutting forces and the excavated rock surface hardness. 2D stereonet models of the resultant force orientation data and estimates of the tool path deviation indicated that the cutting tool experienced significant deflection during cutting. Finally, it was found that cutting geometry and excavated rock surface hardness contributed significantly to variations in the specific cutting energy --Abstract, page iii

Saturation effects on mechanical excavatability of Roubidoux sandstone under selected rock cutting tools

This study investigated the differences in the cutting performance of two rock cutting tools in dry and saturated rock. For this purpose, a permeable quartzose sandstone was subjected to a series of full scale linear rock cutting tests, in both dry and saturated conditions, using a constant cross-section (CCS) disc cutter and a radial drag pick at a constant cutting speed. In this rock, saturation with water reduced the forces acting on the disc cutter by 27-48% (significant at 90% confidence), but also reduced the chip yield by nearly as much. Even though the specific energy of fragmentation went down 8-10%, the difference was not statistically significant. Contrary to the behavior under the disc cutter, water saturation increased the drag pick cutting forces by 9-10%, which is suggestive but not enough to be statistically significant. It did not increase the chip yield by a concomitant amount, however, so the specific energy went up by 28% (significant at 90% confidence). The unexpected differences in the effect of water saturation on the rock fragmentation response to these cutters might be explained by the effects due to their different fragmentation mechanisms, such as the relative size of the crushed zone that forms beneath the cutters. The relationship between cutting speed and rock permeability was expected to be a major factor influencing the effective pressure beneath a cutter in saturated rock. However, load-indentation tests with pore pressure measurement at the same speed showed that the pore pressure within the tested sandstone remained too low to affect the rock fracture process. Other possible mechanisms are discussed --Abstract, page iii

Urban Tunneling Risk Management: Ground Settlement Assessment through Proportional Hazards Modeling

Nowadays, tunnel excavation plays a major role in the development of countries. Due to the complex and challenging ground conditions, a comprehensive study and analysis must be done before, during, and after the excavation of tunnels. Hence, the importance of study and evaluation of ground settlement is dramatically increased since many tunnel projects are performed in urban areas, where there are plenty of constructions, buildings, and facilities. For this reason, the control and prediction of ground settlement is one of the complicated topics in the field of risk engineering. Therefore, in this paper, the proportional hazard model (PHM) is used to analyze and study the ground settlement induced by Tabriz Metro Line 2 (TML2) tunneling. The PHM method is a semi-parametric regression method that can enter environmental conditions or factors affecting settlement probability. These influential factors are used as risk factors in the analysis. After establishing a database for a case study and using a proportional hazard model for surface settlement analysis, and then by evaluating the effect of environmental conditions on the ground surface settlement, it has been found that the risk factors of grouting pressure behind the segment, the ratio of tunnel depth to groundwater level, and drained cohesion strength at a significant level of 5% have a direct effect on the probability of settlement. The results also showed that the effect of grout injection pressure on ground subsidence is more than other parameters, and with increasing injection pressure, the probability of exceeding safe subsidence values decreases. In addition, it has been found that increasing the risk factor for the ratio of tunnel depth to groundwater level reduces the probability of exceeding the safe ground settlement. Finally, increasing the number of risk factors for drained cohesion strength increases the probability of exceeding safe settlement