Performance Of Excavation Research Articles

Calculation of resistance force at firm clay digging with a cylindrical bucket

BACKGROUND: The performance of single-bucket hydraulic excavators affects many areas of activity. This parameter of the machine largely depends on the volume of the material being moved. However, the bucket resistance forces do not allow large buckets to be installed on an excavator. AIM: The paper discusses the design of the bucket which resistance to digging is reduced when it embeds into the ground. This statement has to be verified. METHODS: For this aim, the process of embedding the bucket into firm dry clay is considered. This kind of soil is the most difficult to be processed. Since there is no viscosity in this soil, the equations of spatial problems of elasticity theory are used to describe the process. A number of assumptions are made, and the system of differential equations describing stresses in the soil is solved. RESULTS: The result of the solution is the obtained dependence for determining the normal pressure from the soil in the process of its destruction, which helps to determine the overall digging resistance force. The initial parameters of the soil and bucket of the proposed design, developed for the excavator based on the YuMZ tractor, are described. The initial parameters are substituted into the resulting solution. CONCLUSION: The obtained value of the digging resistance force is significantly lower than the force that the hydraulic drive of an ordinary excavator has to overcome.

Numerical analysis of a deep and oversized group excavation: A case study

Group excavations are composed of several individual excavations adjacent to each other with simultaneous or successive construction sequences (CS), which are distinctive from individual excavation in terms of the performance of excavation. In this study, a hyper-scale 3D finite element model was established to investigate the deformation behavior of a diaphragm wall system retaining a deep and oversized group excavation (DOGE) in Shanghai soft clay deposits. The numerical model simulated the practical construction stages and sequences, and it was verified by a series of comparisons with field measurements. Based on the numerical model, the spatial effect of the performance of DOGE in the process of excavation stages was investigated in this study, which cannot be addressed by limited field measurements. Furthermore, the effects of partition walls and CS on the deformation control were discussed to provide practical suggestions for oversized and deep excavations. The results indicate that the employment of bi-partition walls to divide the oversized excavation into several small pits and mono-partition walls and cross walls to further divide the pits near the metro lines into smaller ones, was proved to have significant effectiveness in controlling the wall deflection and protecting the adjacent metro line. For the partition wall, the magnitude and direction of the wall deflection primarily depended on the initial excavation, while the influence of subsequent excavation activities proved insignificant. Thus, it should be noted that the effect of the initial excavation should be especially concentrated. The findings can help optimize similar DOGE engineering.

Residual strength and critical state of strain softening–hardening considering thermal effect for brittle rocks

Since the post failure of rock has a significant effect on the performance of excavation, the residual strength of rock considering the thermal effect, is important for deep rock engineering, such as sequencing in underground excavation and tunnel support design. From the micromechanical perspective, this paper presents novel models of residual strength and critical state of strain softening–hardening, considering the thermal effect for brittle rocks. The model of the residual strength for brittle rocks was established by considering the thermal effect. Then, the criterion was proposed under for critical state of stress softening and strain hardening by considering the thermal effect. The new models include independent parameters with physical meaning. Finally, the reliability of the proposed model and criterion was verified by comparing theoretical predictions and experimental data. It was found that the proposed models can provide an effective means to predict the residual strength behavior and critical state of strain softening–hardening, considering the thermal effect for brittle rocks.

Numerical investigation of bucket wear and excavation performance with non-spherical materials

Wear significantly affects equipment performance at mining sites, especially when excavating materials with diverse shapes, leading to increased bucket wear and reduced service life. This work combines the co-simulation of multibody dynamics and discrete element method with the Archard wear model to investigate the dynamic interactions between the bucket and non-spherical materials, and the impact of bucket wear on excavation performance. The results indicate that wear is evident on the bottom surface, side surface, and teeth of the bucket throughout the working cycle. The wear patterns observed for different teeth vary, highlighting the importance of maintenance for the middle and side teeth. Compared to spherical particles, ellipsoidal ones cause greater excavating resistance, bucket wear, and hydraulic fluctuations. As wear intensifies, the teeth become blunt, and the bottom surface exhibits unevenness, resulting in reduced payload and increased resistance and hydraulic power. Proposed wear mitigation strategies can help uphold satisfactory operating performance.

Study of the technical parameters dynamics influence on operational performance of hydraulic single-bucket excavators

Introduction. The development of automobile and road construction is a priority in the Russian economy. Timely putting construction projects in commission increases the requirements for planning of execution mechanized works. The operation of transport and technological machines in construction processes for a long time leads to a decrease in their potential capabilities, including operational productivity. The purpose of the proposed article is to improve the method of calculating the performance of a single-bucket hydraulic excavator (EO), taking into account the operating time.Methods and materials. The performance calculation method takes into account the dynamics of the working pressure in the hydraulic system of the working equipment (GRO), the speed of rotation of the crankshaft (PMVC) from the operating time, regression dependencies were used to describe them. The parameters of the law of distribution of the random value of the working pressure in the hydraulic drive and the rate of its fall for the ‘development and recruitment of soil’ operation were also obtained.Results. Processing of the results of production experiments enables to establish the dependence of changes in the working pressure in the hydraulic system during development and gathering soil, as well as for all technological operations of the working cycle, the rotational frequency of the crankshaft of a single-bucket excavator engine on the operating time. The influence of the working pressure in the hydraulic drive, the rotational speed of the crankshaft of the excavator engine on the supply and hydraulic power, the duration of technological operations is studied. The calculation of the operational productivity of a single-bucket excavator is carried out taking into account the dynamics of parameters reflecting its change over operating time.Discussion and conclusions. It has been established that with an increase in operating time, the operating pressure in the hydraulic drive decreases by an average of 12.7-13.0%, and the decrease in the average operating speed of the crankshaft is 4%. The estimated value of the drop in the average hourly operating performance of the EO, taking into account the deterioration of the technical condition, is 55% in the operating time range from 0 to 10,000 operating hours for the Japanese EO ZX 330 model.

The Performance of a Circular Excavation Supported by a Prefabricated Recyclable Structure in a Full-Scale Test

Excavations for underground structures, such as working shafts, underground grain silos, and parking garages, are characterized by uniformity, consistent dimensions, large quantities, and strict timelines. Prefabricated recyclable supporting structures (PRSS) are gaining attention over traditional retaining structures due to their standardized design, efficient construction, and reusability, which suit such excavations better. To validate their performance, full-scale tests are conducted to analyze the deformation and stress characteristics of PRSS. The results show that the average maximum lateral displacement of supporting pile is 0.07% of the excavation depth (He), roughly half that of steel plate. Differences in ground surface settlement behind steel plates and the supporting piles are not as significant as those in their lateral displacements. While the displacement of the supporting piles is insufficient to induce soil movement into the active limit state on the non-excavation side, the circular excavation’s arching effect reduces the earth pressure on this side of the supporting piles below the active earth pressure limit. Furthermore, the earth pressure acting on the steel plates is lower than that acting on the supporting piles, suggesting the presence of a soil arching effect between two adjacent piles. These findings offer valuable insights for guiding the construction of PRSS.

Parametric Study of the Deep Excavation Performance of Underground Pumping Station Based on Numerical Method

Environmental responses to deep excavations are combined results of numerous factors. The effects of some factors are relatively straightforward and can be considered carefully during the design. On the other hand, more features impact excavation-induced performances indirectly, making their influences difficult to be clearly understood. Unfortunately, the complexity and non-repeatability of practical projects make it impossible to thoroughly understand these issues through realistic deep excavation projects. Therefore, parametric studies based on repeatable laboratory and numerical tests are desired to investigate these issues further. This work examines the influence of several key features on excavation-induced displacements through a series of 3D numerical tests. The study includes the choice of soil constitutive models, the modeling method of the soil–wall interface, and the influences of various key soil parameters. The comparison shows that the MCC model can yield a displacement field similar to the HSS model, while its soil movement is greatly improved compared to the MC model. Both the soil–wall interface properties and soil parameters impact the excavation-induced displacement to a large extent. In addition, the influence mechanisms of these parameters are analyzed, and practical suggestions are given. The findings of this paper are expected to provide practical references to the design and construction of future deep excavation projects.

Обоснование оптимальных наработок основных насосов карьерного гидравлического экскаватора

As the pump operates and wears out, the gap in the friction pairs increases and the volumetric efficiency decreases, the pump flow gets reduced, which leads to increasing duration of working and auxiliary operations, the operating cycle of the excavator, a decrease in its productivity and excessive fuel consumption. Infrequent pump replacement can lead to a significant increase in fuel consumption and reduced excavator performance. If the pump is replaced prematurely, its service life will not be used to the full extent. In order to develop a method for establishing optimal operating hours that allow minimizing fuel consumption and the cost of replacing a pump, taking into account operating conditions, a mathematical model of the pump operation is proposed, which makes it possible to obtain an expression for determining the differentiated optimal value of operating time between replacements. A calculation method and a software algorithm have been developed in the MatLab Simulink software suite to calculate the rate of decrease in the volumetric efficiency, as well as to establish the influence of volumetric efficiency on the fuel consumption and performance of a hydraulic excavator to be utilized in the model using the example of the HPV375 pump of the Komatsu PC2000-8 excavator, Based on the proposed mathematical model of the main pumps operation, a method has been developed for calculating the differentiated operating time between replacements of the main pumps of a mining hydraulic excavator, taking into account the rate of decrease in volumetric efficiency, replacement costs and damage due to changes in productivity and excessive fuel consumption. The dependence of the rate of changes in the volumetric efficiency of the pump is presented for the excavation, viscosity, contamination and temperature of the working fluid parameters. A coefficient of “reserve of partial engine power transferred to the pump” is proposed, determined by the ratio of the difference between the average maximum and initial partial power to the value of the initial partial power, which allows estimation of the operating time of the main pumps without affecting productivity of the excavator.

Assessment of safety of masonry buildings near deep excavations: impact of excavations on structures

The knowledge of impacts and the load-bearing capacity of unstrengthened/strengthened structures is a crucial source of information about the safety of masonry buildings near deep excavations, especially in dense urban areas. Incorrect calculations made for such designs can seriously affect not only an analyzed object, but also the adjacent buildings. The safety of masonry buildings can be determined by many factors that are closely related to the hazards presented during the performance of deep excavations. These factors are at first identified and then prioritized. The AHP process in the multi-criteria analysis was used to support the decision-making process related to the verification of factors affecting the safety assessment of masonry buildings in the area of deep excavations. The proper design of building structures, including the verification of the structure strengthening near deep excavations, was found to be the most significant factor determining the safety of such buildings. The methodology for proceeding with the verification of ultimate (ULS) and serviceability (SLS) limit states in accordance with the literature data, current regulations, such as Eurocode 6 and other design standards, and know-how of the authors, described in this paper was the next stage of the discussed analysis.

Semi-empirical model for abrasive particle velocity prediction in abrasive waterjet based on momentum transfer efficiency

AbstractAbrasive waterjet (AWJ) is a technology that removes a target material with an abrasive accelerated by ultra-high-pressure water. Recently, its application for rock excavations in civil and geotechnical engineering has increased. AWJ excavation performance is affected by the abrasive velocity formed by momentum transfer during mixing and acceleration. The abrasive velocity varies owing to changes in the abrasive flow rate, focusing tube diameter, and focusing tube length. In this study, the momentum transfer efficiency (MTE) according to the abrasive flow rate and focusing tube geometry was investigated by a numerical analysis to better understand the multiphase flow inside the AWJ system. The MTE was defined based on the theoretical relationship between the abrasive velocity ratio and focusing tube factor, and evaluated through the empirical relationship between the water stiffness and focusing tube length. The optimal abrasive flow rate for generating efficient MTE was approximately 15 g/s, which enabled economical and effective acceleration of abrasive particles. Accordingly, a prediction model based on the derived MTE was developed for the final abrasive velocity generated at the tip of the focusing tube. Using the prediction model, it is possible to evaluate the comprehensive relationship between various AWJ parameters. Based on the prediction model, the abrasive–water flow ratio to generate the optimal abrasive velocity was 0.83. The developed prediction model provides guidelines for selecting the optimal focusing tube geometry and applying an economical abrasive flow rate when designing an AWJ system.

3D FEM Back Analysis of the Observed Performance of a Very Deep Excavation in the Historical Center of Naples, Italy

3D FEM Back Analysis of the Observed Performance of a Very Deep Excavation in the Historical Center of Naples, Italy

Data-driven excavation trajectory planning for unmanned mining excavator

In autonomous mining scenarios, excavation trajectory planning plays a significant role since it considerably influences the working performance of the unmanned mining excavator (UME). Aiming at the limited dynamical characterization of traditional theoretical methods that yield unsatisfactory performance in trajectory planning, herein we propose a data-driven excavation trajectory planning framework based on deep learning for improving the operation performance in autonomous excavation scenarios. First, the actual sensing data is collected, and a temporal convolutional recurrent neural network (TCRNN) combining stacked dilated convolutions with an attention-based sequence to sequence (Seq2Seq) module is proposed to predict the digging force accurately. Then, the surrounding material profile is perceived based on Lidar, and a polynomial response surface is performed to point cloud reconstruction. Considering mining efficiency, energy consumption and stability in the excavation process, a multi-objective function is constructed, and a data-driven excavation trajectory planning framework based on TCRNN is established. To obtain the accurate solution of the planning framework, a discretization strategy based on Radau pseudospectral method is developed to model solving to ensure the working performance in autonomous mining. An actual unmanned prototype experiment is performed to investigate the performance of the proposed framework. The results demonstrate the effectiveness and superiority of the proposed framework.

Prediction of the tunnelling advance speed of a super-large-diameter shield machine based on a KF-CNN-BiGRU hybrid neural network

The tunnelling advance speed (TAS) of a super-large-diameter tunnel boring machine (TBM) significantly affects project progress and safety. Effective prediction of the TAS of a TBM is crucial for early warning and evaluation of its excavation performance. This paper proposes a model based on convolutional neural network (CNN) and bidirectional gated recurrent unit (BiGRU) to predict TAS. This model can more effectively extract and retain many features; additionally, it considers the temporal relationships among the operating parameters of the TBM. Additionally, a Kalman filter (KF) is incorporated into the model to effectively remove input parameter noise, leading to a more accurate prediction of TBM excavation speed. A case study indicated that the pressure of the excavation chamber and the pitch angle of the shield tunnelling machine were correlated with the advance speed. The research results show that the proposed model can accurately and effectively predict TAS.

Comprehensive Performance Evaluation of an Unmanned Excavator Based on Signal Stability Extraction

The comprehensive performance of unmanned excavators is crucial for the development and optimization of the field of construction machinery. To effectively improve the unmanned excavator to meet the needs of the market, it is imperative to quantify the evaluation method of the comprehensive performance of unmanned excavators. In this study, an evaluation method combining a fuzzy analytic hierarchy process and multivariate image area analysis method is proposed. Firstly, based on the feature extraction of the signal stability of the unmanned excavators, fifteen evaluation indexes were proposed. Then, the case study is used to obtain the scores corresponding to these indexes. The fuzzy analytic hierarchy process is applied to determine the relative weight of the selected evaluation criteria, in which the uncertain and imprecise judgments of decision makers are converted into fuzzy numbers. At the same time, the braking performance of the three types of unmanned excavators was comprehensively evaluated and ranked using the multivariate image area analysis method as an empirical example. Finally, a weight analysis is performed to check the robustness of the ranking results. The results show that the proposed method is effective and feasible. It provides a reference for the performance improvement and efficiency optimization of unmanned excavators.

Performance analysis of hydraulic excavators in complex excavation environments and different bucket trajectories

Simulations of excavation operations not only help understand how excavators perform in specific environments but also can be used to optimise operating parameters. In this work, we explore the performance of hydraulic excavators under conditions of cohesive and size-dispersed materials and different bucket trajectories. The results indicate that with the cohesion increasing, the spillage of particles from the bucket is reduced, but the hydraulic power fluctuates greatly due to the strong collision of particle aggregates on the bucket. As the particle size distribution turns wider, small particles exert an intensive interaction force on the bucket, and the stress distribution on the bucket becomes wider. Therefore, some suggestions are given for practical excavation operations in different stockpile scenarios. Additionally, the bucket can be initially placed close to the base of the stockpile to achieve low specific energy consumption and high productivity.

Performance of tracked excavators equipped with grapple-saw stacking treetops in poplar plantations

ABSTRACT In recent years, the cost of manpower increased in Southern Europe. This has encouraged companies to improve the mechanization level of all activities. Purpose-built machines are very expensive, so in this transition phase, there is a tendency to purchase multipurpose machines to reduce depreciation costs. In this scenario, excavators play a fundamental role because they can be used in many activities by changing the working tools. In poplar plantations, excavators with grapple saws and tracks are usually used to move the residual biomass. This work aimed to analyze the performance of excavators with a grapple-saw during the stacking of residual biomass in poplar plantations. Six excavators that varied in power and mass were analyzed. The data analyzed showed that productivity is directly proportional to the machine’s power and mass (0.15 t h−1 kW−1 and 0.75 t h−1 t−1). Furthermore, productivity is linked to the opening size of the grapple (6.43 t h−1 m−1 of opening). In conclusion, on the basis of the results obtained, it is possible to confirm that the excavators can be valid machines also in forestry activities independently of their nominal power and gross mass.

The major impact of coal mining service activities to GHG emissions: Case study at PT Bukit Makmur Mandiri Utama (BUMA) jobsite Binsua and Lati

Indonesia is ranked 9th as a country contributing 1.6% to total global emissions and is committed to reducing GHG emission targets unconditionally by 29% and conditionally by 41 % compared to the business as is a scenario of 834 Mt CO2e and 1,185 Mt CO2e, respectively, in 2030. Mining industry has been viewed as one of the largest contributors to GHG emission with a specific process that inevitably generates it. Mobile sources produce direct GHGs of CO2, CH4, and N2O. This study is intended to compare the results of the emission intensity and impact of coal mining production activities as the compounded GHG to discern which of them yields the enormous amount of emission. The method is concentrated only on scope 1 and Tier 2 as a direct responsibility of BUMA as a coal mining contractor. The total amount of fuel consumption GHG emissions was 512,193 tCO2e at Binsua and 742,006 tCO2e at Lati. The composition of the highest emission equipment at Binsua and Lati in 2020-2021 is dump trucks, loaders, and dozers. BUMA will continue to develop potential GHG roadmaps and focus on the performance of dump trucks and excavators, as they are responsible for more than 70% of scope 1 emissions.

ОПТИМИЗАЦИЯ ПАРАМЕТРОВ ТЕХНОЛОГИИ РАЗРАБОТКИ ПОЛУСКАЛЬНЫХ ВСКРЫШНЫХ ПОРОД ЭКСКАВАТОРНОАВТОМОБИЛЬНЫМИ КОМПЛЕКСАМИ С ПРИМЕНЕНИЕМ МЕХЛОПАТ

The article presents the results of research on the optimization of the parameters of the technology for the development of semi-horizontal overburden by excavator-automobile complexes using mechlopats. The available methods for calculating the productivity of mechlopats are analyzed. An empirical universal dependence of the calculation of the value of the excavation coefficient on the average diameter of the piece has been established for all types of modern mechanical shovels, which makes it possible to determine the change in the value of the replaceable operational performance of mechanical shovels from the value of the average size of pieces of blasted rocks. The results of statistical processing of comparing the values of the excavator performance installed in production conditions with the calculated ones showed that the coefficient of variation when calculated according to the proposed (new, universal) formula is almost two times lower than the known (used) ones. An enlarged block diagram of a complex algorithm for optimizing the parameters of the EACMS is determined by selecting the value of the specific consumption of explosives, the type of a mechanical shovel, dump truck, drilling rig and bulldozer.

Dynamic digging force modeling and comparative analysis of backhoe hydraulic excavators

The evaluation of excavator performance relies heavily on digging force, which serves as a crucial indicator. However, the accuracy of performance assessment is hindered by the absence of a suitable method to characterize the dynamic digging capacity of excavators. This study addresses this limitation by proposing an approach to establish a set of solution-limited inequalities for dynamic digging force. The approach incorporates D’Alembert’s principle and composite digging, while considering the influence of inertia force. Furthermore, to mitigate the issue of bucket tooth tip trajectory shaking caused by discontinuous posture during excavation, an amount of measurement data from a 20-ton machine is utilized to construct a consistent theoretical digging trajectory. The theoretical trajectory is subjected to numerical verification to determine the dynamic digging force along the trajectory. A comparative analysis is then conducted, contrasting the obtained dynamic digging force with different theoretical digging forces and measured resistances. Additionally, the dynamic digging forces within the selected digging area of the machine are characterized, without accounting for attitude continuity. The findings demonstrate that the dynamic digging force effectively captures the excavator’s performance along the trajectory, and it also provides an excellent characterization of the digging force at discrete digging spots.

Comparison of Tunnel Construction Cycle with NTNU Model for the Headrace Tunnel of Seti Khola Hydropower Project

Achieving smooth and efficient blasting of tunnel walls is a challenging task. Tunneling performance and advancement can best be performed with proper and effective blasting techniques in drill and blast techniques. In this manuscript, the Seti Khola hydropower project's headrace tunnel's real-time statistics are used to compare the overall performance of tunnel excavation for the widely used blasting approach. The headrace tunnel's 663 meters of observed and recorded length comprises rocks with weak to medium blastibility. According to the Q-system, this tunnel section's rock mass quality class ranges from good to bad. The rock type found has a monotonous sequence of metasandstone and phyllite with quartz partings and discontinuities filled with clay to silt. A variation in the excavation cycle is observed in relation to the presence of different rock mass classes. Ultimately, the NTNU model is compared and analysis is done on the drilling patterns and cycles of tunnel building. It was discovered that using the NTNU model for tunnel excavation presents a significant opportunity to enhance performance.