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Understanding the variation patterns of tunnel boring machine (TBM) operational parameters is crucial for assessing engineering geological conditions and quality grades of surrounding rock within tunnels. Studying the multifractal characteristics of the TBM operational parameters can help identify the patterns, but the relevant research has not yet been explored. This paper proposed a novel classification model for quality grades of surrounding rock in TBM tunnels based on multifractal analysis theory. Initially, the statistical characteristics of eight TBM cycle data with different grades of surrounding rock were explored. Subsequently, the method of calculating and analyzing the multifractal characteristic parameters of the TBM operational data was deduced and summarized. The research results showed that the TBM operational parameters of cutterhead torque, total thrust, advance rate, and cutterhead rotation speed have significant multifractal characteristics. Its multifractal dimension, midpoint slope of the generalized fractal spectrum, and singularity strength range can be used to evaluate the surrounding rock grades of the tunnel. Finally, a novel classification model for the tunnel surrounding rocks based on the multifractal characteristic parameters was proposed using the multiple linear regression method, and the model was verified through four TBM cycle data containing different surrounding rock grades. The results showed that the proposed multifractal-based classification model for tunnel surrounding rocks has high accuracy and applicability. This study not only achieves multifractal feature representation and surrounding rock classification for TBM operational parameters but also holds the potential for adaptive adjustment of TBM operational parameters and automated tunneling applications. [ABSTRACT FROM AUTHOR]

Drilling motors are widely used in unconventional oil and gas exploration. Due to the increased nonproductive time and drilling costs brought about by accidental damage to drilling motors, predictive maintenance for drilling motors is necessary to optimize asset utilization. However, service companies face significant challenges in achieving predictive maintenance: operational data acquisition, automated statistics analysis, and drilling state recognition. This paper presents a miniature vibration recorder, an automatic statistical analysis method, and a layered recognition algorithm to resolve these challenges and improve tool maintenance efficiency. The designed recorder can be installed in the catch of a conventional mud motor to record drilling dynamics over a drilling motor's entire operation cycle. Timeseries data from the recorder can be used to automatically generate operation statistics, mitigating the costs incurred by manual data analysis. The layered recognition algorithm then enables the automatic identification of drilling operation states, i.e., surface, downhole non-drilling, downhole sliding, and downhole rotation. The solutions were validated by deploying the recorder in drilling field runs and analyzing recorded data using the associated design software, yielding a functional data collection, automatic data statistical analysis, and operation state recognition accuracy of 95%. Through achieving improved data collection and analysis, the recorder and software introduced in this work can notify motor owners of the detailed operation history of their tools and enable informed preventive maintenance. [ABSTRACT FROM AUTHOR]

In this paper, importance of tunneling and their methods are discussed. Most importantly, Metro projects are becoming current trends in India and one of the popular underground Metro which is existing in Kolkata with latest under water tunnel project is presented in this paper. It is an important project for Civil Engineers with some project highlights are given for upcoming generation. As underwater tunnel is first of its kind and gaining popularity. [ABSTRACT FROM AUTHOR]

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The specialized equipment utilized in long-line tunnel engineering is evolving towards large-scale,multifunctional, and complex orientations. The vibration caused by the high-frequency units during regular operation is supported by the foundation of the units, and the magnitude of vibration and the operating frequency fluctuate in different engineering contexts, leading to variations in the dynamic response of the foundation. The high-frequency units yield significantly diverse outcomes under different startup conditions and times, resulting in failure to meet operational requirements, influencing the normal function of the tunnel, and causing harm to the foundation structure, personnel, and property in severe cases. This article formulates a finite element numerical computation model for solid elements using three-dimensional elastic body theory and integrates field measurements to substantiate and ascertain the crucial parameter configurations of the finite element model. By proposing a comprehensive startup timing function for high-frequency dynamic machines under different startup conditions, simulating the frequency andmagnitude variations during the startup process, and suggesting functions for changes in frequency and magnitude, a simulated startup schedule function for high-frequency machines is created through coupling. Taking into account the selection of the transient dynamic analysis step length, the dynamic response results for the lower dynamic foundation during its fundamental frequency crossing process are obtained. The validation checks if the structural magnitude surpasses the safety threshold during the critical phase of unit startup traversing the structural resonance region. The design recommendations for high-frequency units' dynamic foundations are provided, taking into account the startup process of the machine and ensuring the safe operation of the tunnel. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mathematics, Mechanics & Computer Science is the property of Al-Farabi Kazakh National University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Tunnel boring machine (TBM) tunnel construction in composite strata relies heavily on understanding the rock-breaking characteristics of TBM cutters and optimizing cutter spacing and penetration. Utilizing a full-scale rock rotary cutting machine (RCM), this study conducted rock-breaking tests with disc cutters under varying rolling radii. An analysis of rock debris shape and cutter behavior provided insights into rock-breaking mechanisms. Two main types of rock fragments were identified, with both shear and compression failure observed during cutter–rock interactions. The influence of the rolling radius and cutter spacing on cutter forces was analyzed, along with numerical modeling using the particle flow method. Optimal cutter selection in soft–hard composite strata should prioritize cutter force, with the greatest force required in hard rock. Cutter force increases with penetration, while the force difference between cutters decreases with reduced cutter spacing. These findings offer practical guidance for efficient rock-breaking in composite geological formations during tunnel construction. [ABSTRACT FROM AUTHOR]

A viscous coupling is a simple device that transmits torque by shearing an oil film between one or more pairs of discs that are moving in relation to one another. Due to their many advantages, viscous couplings are studied in many applications such as fan transmissions in vehicles, pumps, winches, belt conveyors, wind turbines, tunnel boring machines. Using a CFD Software, this study examined how grooves affected the performance of a viscous coupling. The main objective of the reported work is to study the flow of the fluid film, the total temperature and the torque of a viscous coupling that is operating in different conditions. [ABSTRACT FROM AUTHOR]

In tunnel construction with tunnel boring machines (TBMs), accurate prediction of the remaining useful life (RUL) of disc cutters is critical for timely maintenance and replacement to avoid delays and cost overruns. This paper introduces a novel hybrid model, integrating fundamental and data-driven approaches, to enhance wear prediction of TBM disc cutters and enable accurate RUL estimation. The fundamental model is improved by incorporating composite wear mechanisms and load estimation techniques, showcasing superior prediction accuracy compared to single-mechanism models. Additionally, the hybrid model innovatively incorporates a data-driven supplementary residual term into the improved fundamental model, leading to a high-performance wear prediction model. Using actual field data from a highway tunnel project in Shenzhen, the performance of the hybrid model is rigorously tested and compared with pure fundamental and data-driven models. The hybrid model outperforms the other models, achieving the highest accuracy in predicting TBM disc cutter wear (mean absolute error (MAE) = 0.53, root mean square error (RMSE) = 0.64). Furthermore, this study thoroughly analyzes the hybrid model's generalization capability, revealing significant impacts of geological conditions on prediction accuracy. The model's generalization capability is also improved by expanding and updating the data sets. The RUL estimation results provided by the hybrid model are straightforward and effective, making it a valuable tool by which construction staff can monitor TBM disc cutters. [ABSTRACT FROM AUTHOR]

The Ylvie model is a novel method towards transparent Tunnel Boring Machine (TBM) data analysis for tunnel construction. The model innovatively applies machine learning to automate friction loss computation per stroke, enhancing TBM performance prediction in varying geomechanical environments. This research considers the complexities of TBM mechanics, focusing on the Thrust Penetration Gradient (TPG) and shield friction influenced by geological conditions. By integrating operational data analysis with geological exploration, the Ylvie model transcends traditional methodologies, allowing for a comprehensible and specific determination of the friction loss towards more precise penetration rate prediction. The model's capability is validated through comparative analysis with established methods, demonstrating its effectiveness even in challenging hard rock tunneling scenarios. This study marks a significant advancement in TBM performance analysis, suggesting potential for the expanded application and future integration of additional data sources for comprehensive rock mass characterization. [ABSTRACT FROM AUTHOR]

Although a shield tunneling machine is intended to excavate a tunnel along its planned alignment, deviations occur between the planned alignment and the measured alignment, which must be corrected. These operations are time‐consuming, and it is difficult to correct deviations. However, related studies have been unable to automatically calculate the optimum operation parameters. Therefore, this study sought to use machine learning to develop an autopilot model, which is a method to automatically calculate optimal operation parameters of the shield machine for straight and curved sections of the planned alignment in both plan and longitudinal views using support vector regression. As a result, it could automatically calculate operation parameters that predict a shield machine that excavates with the same or better excavating accuracy of a skilled operator and contributes to the automation of shield machine operation. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the bone collection capacity of bur drill systems used in implant surgery with different diameters, lengths, and drilling speeds. Materials and Methods: This study was performed on bovine ribs. Two bur drill systems were studied: Implantium (Dentium) and Straumann (Institut Straumann). The groups were divided into subgroups according to the bur diameter. As a result, there were four Implantium subgroups (3.3, 3.8, 4.3, and 4.8 mm) and three Straumann subgroups (3.3, 4.1, and 4.8 mm). In addition, for each bur diameter, the bone collection capacities of the drill systems were evaluated at three different drilling speeds (150, 250, and 400 rpm) and two bur lengths (10 and 12 mm). The diameter, length, and speed changes were performed, and the results were compared between the two drill systems. Results: The mean bone weight collected by using the Straumann burs was higher than that of the Implantium burs at each drilling speed and bur length. Using the Straumann system, the different drilling speeds/lengths of the burs had no impact on the bone collection capacity, irrespective of the bur diameter (P > .05). However, the drilling speeds/lengths of the Implantium system resulted in a statistically significant difference in the same diameters (P < .05). Conclusion: Both bur systems were suitable for autogenous graft collection for bone grafting in implant surgery, but the Straumann burs were more successful than the Implantium burs. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate if repeated use of pilot and depth drills for implant site preparation in combination with resterilization leads to any significant changes in cutting edges or in preparation times. Materials and Methods: With drills of different lengths and widths (pilot, parallel, and tapered), osteotomies were performed under constant conditions in pig jaws. After each osteotomy, the drills were processed and sterilized. The required time for finishing the osteotomy was noted and analyzed. At the end of each osteotomy cycle, consisting of 10 osteotomies and 10 sterilizations, the cutting edge wear of the drill was analyzed using scanning electron microscopy. Unused but sterilized drills served as a control group. Results: There was no statistically significant difference in the evaluated wear between pilot drills and depth drills as well as between the test and the control group. After 60 osteotomies, implant drills showed considerable signs of wear at the major cutting edge (P > .05). Osteotomy led to a significant increase in the drilling time. While pilot drills showed an increase of drilling time of the factor 33.3, and the tapered drills of the factor 5.37, the parallel drills remained constant in their performance. Conclusion: Within the limitations of this study, it can be concluded that the process of sterilization as well as the number of performed osteotomies play a major role in the wear of the cutting edge and the performance of implant drills. [ABSTRACT FROM AUTHOR]

The actuator is a key component of the creaming tool in drilling applications. Its jet performances determine the effective reaming efficiency. In this work, a new selective reaming tool is proposed and the RNG k-e turbulence model is used to calculate its internal and external flow fields. In particular, special attention is paid to the design of the flushing nozzle. The results show that the jet originating from the flushing nozzle has a significant influence on rock cutting and blade cooling effects. In turn, the jet performances depend on geometric structure of the creaming actuator. In this framework, a conical-cylindrical nozzle with a diameter of 7 mm is initially considered as a basis to implement a strategy to optimize the structural parameters of the reaming actuator, and improve the related side tracking reconstruction technology. [ABSTRACT FROM AUTHOR]

The cutting process of the cantilever tunneling machine mainly generates excitation through the cutting motor or the hydraulic cylinder driven by the hydraulic system. Regardless of the driving method, the frequency width of the excitation system is limited, difficult to control, and the excitation effect is poor. Therefore, in order to improve excavation efficiency, the excitation system parallel to the original cutting and rotating system is designed. Based on the excitation characteristics caused by alternating fluid flow, the core component of the excitation system, hydraulic exciter, is designed, and the dynamics and dynamic characteristics of the excitation system are analyzed. Based on AMESim software, analyze the impact of factors such as pump displacement, excitation frequency, and pipeline parameters on the operational performance of the electro-hydraulic vibration cutting system, and conduct experimental verification by building a cutting test bench. The experimental results show that as the inner diameter of the pipeline increases, the fluctuation at the acceleration turning point decreases in each cycle and approaches the peak faster. As the excitation frequency increases, the cutting acceleration of the electro-hydraulic excitation cutting system decreases first and then increases, verifying the accuracy of the simulation results. In the experiment, it was found that the acceleration transformation range of the cutting head of the excitation system is the smallest and most stable when the excitation frequency is 30 Hz. In order to verify that the excitation frequency of 30 Hz is the optimal frequency, further contact force tests were conducted on the cutting teeth. It was found that when the hydraulic excitation system adds a 30 Hz excitation frequency, the contact force on the cutting teeth is the smallest. It is more conducive to reducing the damage and wear of the cutting head, and the cutting effect of the cutting head is more obvious. The research results are beneficial for improving the cutting performance of the electro-hydraulic excitation cutting system, providing theoretical support for the selection of cutting parameters for excavation machinery and hydraulic excitation, and improving the existing theoretical system for active excitation cutting vibration analysis of excavation machines. [ABSTRACT FROM AUTHOR]

Segmental lining structures constructed by shields/tunnel boring machines are often subjected to uneven longitudinal cross-section torsion as a result of eccentric external loads, which is extremely adverse to tunnel safety but has not received sufficient attention for a long time. To figure out the torsional performance of segmental tunnels, it is essential to assess the longitudinal torsional stiffness and active-torsion-rejection capability of a segmented tunnel. The aim of the paper is to derive an analytical solution to the longitudinal torsional stiffness of a segmental tunnel with existing elliptical deformation. The longitudinal torsional stiffness under different internal force combinations is deduced considering the longitudinal axial force and bending moment based on the equivalent continuous model and force balance equation. The validity of the analytical solution is verified by comparing it with finite element method results. Then, a parametric analysis, using the new analytical solution, is included to investigate the effect of the key parameters on torsional behaviors, including the segment size, the bolt size and the transverse bending stiffness, etc. It is found that: (1) the longitudinal torsional stiffness efficiency (LTSE) of the segmental tunnel decreases with the rise of segment thickness to diameter ratio but increases with the ring width to diameter ratio; (2) the LTSE reduces with the increase of the effective shear length but rises with the diameter of bolts; (3) the LTSE increases rapidly with the ratio of compression-torsion or bending-torsion. Furthermore, the envelope curve of the critical load (N0, M0) for a tunnel to actively resist a certain internal torque is given. The proposed solution can be easily utilized to determine the longitudinal torsional stiffness of segmental tunnels and is an effective tool for tunnel design and maintenance. [ABSTRACT FROM AUTHOR]

The proposed underground tunnel for Mass Rapid Transit Line 1, Dhaka brings immense attention to the engineers and experts not only because of its construction challenges through a densely-built city, but also for the potential tunneling-induced ground settlements. This very preliminary study investigates the ground surface movement due to the progression of the tunnel boring machine (TBM) using numerical analysis. A series of finite element (FE) models have been developed using PLAXIS 3D, in which Mohr-Coulomb (MC), modified Cam-Clay (MCC), and hardening soil (HS) have been considered. The in-field data of Mashhad Metro Line-2 have been compared to verify PLAXIS 3D's efficacy in tunnel modeling. Subsequently, the outcomes of the FE analyses are compared with the existing empirical formulas. The PLAXIS 3D analysis considering the MCC soil model exhibits strong agreement with the real monitored data, with a variance of only 3.85%. After simulating different stages of the tunnel construction, results are reported in terms of the distance of the inflexion point from the center, the settlement trough pattern, the maximum transverse settlements, and the vertical settlements. They are also compared with the established empirical formula. In order to comprehend the surface settlement with various tunnel depths and diameters, a parameter dependency study has been carried out. The analysis findings showed that increasing the TBM's depth and radius causes the inflexion point's distance from the center of the tunnel to increase by 4% and decrease by 5%, respectively. It is also observed that as tunnel depth increases, the overall settlement of the tunnel lowers by 11% for every additional 5 meters of depth. The MCC model, out of the three, exhibits the most accurate value of the settlement compared to that obtained from the empirical solutions, and also the best-fit form to the Gaussian curve. [ABSTRACT FROM AUTHOR]

Rock condition perception based on tunnel boring machine (TBM) data is of great importance for not only ensuring tunnel boring safety but also improving construction efficiency. The prediction of TBM boring responses (i.e., torque and total thrust of the cutterhead) largely determines the reliability of rock condition perception. In this paper, a new architecture of a two-dimensional convolutional neural network (2D-CNN) with a dual-input strategy is proposed to predict the TBM responses. The TBM Lot 3 of the Yinsong project in Jilin province, China, is taken as the case study in this paper. Two types of models that follow different learning strategies are compared: one is defined as the point model, which only learns data of the stable phase, and the other is defined as the line model, which learns data from both the loading and stable boring phases. The line model is further improved by the weighted loss function method. The results indicate that the strategy of learning data from both the loading phase and stable boring phase and increasing the weight of samples from the stable phase is shown to be optimal in predicting TBM boring responses. In terms of learning strategies, the line model can learn the influence of active control parameters on passive response parameters, but the point model cannot. In terms of machine learning algorithms, 2D-CNN has the best performance, with R2 values of 0.865 and 0.923 for torque and total thrust, respectively. The proposed line model can overcome the problem that the traditional model failed to learn the influence of control parameters. Such a model can provide a solid base for the timely optimization of the control parameters in TBM boring process. [ABSTRACT FROM AUTHOR]

In shield tunnel boring machine (TBM) tunnel construction, grouted pea gravel is used to fill gaps between the surrounding rock and segment rings, acting as a connecting layer that significantly impacts the support performance of the segment ring. This study first obtained the mechanical parameters of pea gravel through experiments, followed by an in-situ investigation to analyze the stress and surface settlement law of the segment ring during TBM construction. A discrete-continuous coupling model was then employed to examine the load transfer process at the micro level between the surrounding rock, pea gravel, and segment ring. Finally, physical model tests were conducted to compare the stress characteristics of the segment ring under different states of pea gravel during continuous loading. The findings reveal that loose pea gravel fails to sufficiently transfer the surrounding rock load to the segment ring, resulting in inadequate support and continuous surface settling until the pea gravel is consolidated. The degree of compression of loose pea gravel directly affects the contact force acting on the segment ring and its supporting effect on the surrounding rock. Moreover, the ultimate bearing capacity of the segment decreases when the pea gravel is loose. The state change of pea gravel resulting from grouting plays a crucial role in the supporting effect of the segment ring; thus, simultaneous grouting is necessary during tunnel construction in unstable strata or insufficient pea gravel filling. [ABSTRACT FROM AUTHOR]

The tool structure is an important factor affecting the damage of CFRP/Ti stacks machining. However, the impact of tool structure on the formation process of stacks hole damage cannot be fully revealed through experimental methods alone. In contrast, finite element simulation can effectively overcome the limitations of experiments. In this study, a numerical simulation model is established to investigate the relationship between step drill structure and formation process of CFRP/Ti stacks hole damage. Based on this, the research discusses the effect of step drill structure on the burr height of Ti layer, delamination of CFRP, aperture deviation, defects in hole surface. The results show that when the stacking sequence is CFRP to Ti, the burr height of Ti at hole exit decreases first and then increases with the rising of the ratio of primary drill bit diameter to secondary drill bit diameter (kd). When kd is 0.6, the burr height of Ti at hole exit is the lower. As kd increasing from 0.4 to 1.0, delamination factor of CFRP increases by 2.57%, which are affected little by the step drill structure due to the support of Ti. Besides, the aperture size deviation decreases first then increases with the rising of kd, and the minimum aperture size deviation is 2.09 μm when kd is 0.6. In addition, as kd is 0.6, the hole wall defect is fewer. In conclusion, step drill with kd of 0.6 is suitable for drilling of CFRP/Ti stacks. [ABSTRACT FROM AUTHOR]

Copyright of Scientific Bulletin of National Mining University is the property of National Mining University, State Higher Educational Institution and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The oversized cargo transportation market in Poland actively participates in developing the economy, providing services necessary for implementing large infrastructure and industrial projects on a national and European scale. Development and functioning of this sector in the EU and globally requires overcoming many organizational, technical and administrative barriers and difficulties, and the authors of several publications indicate how these services are developing. The current study contains a detailed analysis of data from 2001-2022. The paper characterizes the changes in particular years, indicating the main causes of the occurring processes, and defines the existing trends. It presents the legal framework that regulates the functioning of the domestic market. Moreover, it discusses the number of permits and the value of fees for issuing permits collected by the General Directorate for National Roads and Motorways (Generalna Dyrekcja Dróg Krajowych i Autostrad, GDDKiA) over two decades. The article also evaluates trends concerning the number of licenses with more than a 50% decrease compared to the maximum in 2008. It assesses the course of changes in values, which in 2021 reached their highest level during the period under assessment. Furthermore, it discusses the differences in the number of permits issued and applications submitted in 2014-2022. It describes the structure of the number of permits issued in categories IV-VII in 2014-2020 and categories III-V in 2021-2022. It characterizes the course of the largest operation in the history of Polish road haulage - the transport of an abnormallysized TBM (Tunnel Boring Machine) - in terms of requirements and problems that occurred during the preparation and fulfilment of this order and were typical for the functioning of the sector. The evaluation provides the basis for summaries and conclusions on the development and condition of the oversized cargo transportation sector in the Polish road transport sector. [ABSTRACT FROM AUTHOR]

Tunneling projects face several risks during the execution stage that affect the execution objectives (cost, time, quality, and safety). This study aimed to define the main execution activities of machinery tunnels with the associated risk factors and to develop a model for evaluating and analyzing the effects of the risk factors on the execution stage. The recognized activities of executing tunnels included the following: (A01) thrust and reception shaft installation; (A02) machine setup and break-in; (A03) machine progression and lining placing; and (A04) machine break-out and removal. Additionally, thirty-two risk factors associated with these activities were identified. Risk factor probability of occurrence and impacts on cost, time, quality, and safety were determined. Due to this risky and uncertain environment, the fuzzy logic method was applied for developing a model to analyze the effects of the risks on the tunneling process. The model was applied and verified using data collected in Egypt. Many correlations were determined among risk factors that affected tunneling execution objectives, resulting in close relationships with each other. The results emphasized many significant risk factors, such as "conflict between technical geological report and the ground nature", and "shaft wall damage during break-out". A03, which is related to machine progression and lining placing, was declared the riskiest activity group during tunneling execution. Further, safety was rated as the objective most affected by risks. The risk model presented in this study can be modified and applied to other cases, while the results and key risks can support the decision-makers who deal with tunneling construction. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate a new guided drill system (MIPS) for placement of bone-anchored hearing systems (BAHS) with respect to cutting performance, generation of heat, and distortion of the bone during drilling and compare it with a conventional drill system (Ponto). Further, the role of irrigation and drilling procedure with respect to the degree of heat generation was evaluated. Materials and Methods: Compact artificial bone was subjected to each drill in the two systems (conventional vs guided) while measuring thrust force, torque, and temperature. The temperature changes, induced during different drilling procedures, were measured by thermocouples positioned 0.5 mm from the periphery of the drill tract. The degree of bone damage was evaluated histologically after drilling in bovine, compact, tibial bone. Results: The mean thrust energy was significantly lower for the drills of the guided system compared with the corresponding conventional drills. In contrast, the mean torque energy was higher using the guided system but only for the initial guide drilling step. Whereas twist drills in combination with a guided drilling approach (MIPS) generated relatively more heat, especially during a prolonged drilling sequence, it was more forgiving in the case of impaired irrigation. The histologic evaluation showed relatively more even cut surfaces and fewer microcracks in the osteotomy wall using the guided system compared with the conventional system. Conclusion: Provided the clinically recommended drilling procedure was adhered to, the absolute temperatures using either a conventional drill system or a guided drill system were below the threshold for thermally induced tissue damage. This study suggests that the guided MIPS system conveys a promising design for an efficient and still-safe osteotomy site preparation for BAHS placement. [ABSTRACT FROM AUTHOR]