Additional Load Research Articles

Reinforcement solution of damaged load-bearing frame structure in a coal power plant for additional loads

Significant subsoil deformation and additional loads from the new denitrification unit caused a major problem with the load-bearing capacity of the coal power plant. It was necessary to perform an advanced assessment of the technical condition of the structure. Laser scanning (LiDAR) were used to obtain detailed data upon structure. Based on the analysis of the point cloud, the location of the column axes was determined, which allowed to determine the global and local displacements of the structure. Spatial models of the structure were created. Non-linear analyses of the structure were carried out using two types of models: 1) global beam-shell 3D models of the boiler room used to calculate the magnitude of internal forces and deformations of the structure; 2) local beam-shell detailed models of selected structural elements. Based on the results of the calculations, necessary reinforcement of the structure was designed and successfully implemented. Advanced analysis of the structure using laser scanning, subsoil monitoring and complex numerical models made it possible to perform only local reinforcements of the entire complex structure.

Enhancement Seismic Response of a Bored Tunnel Using Isolation for the Challenge of a Faulted Rock Crossing

The tunnel boring method (TBM) is a widely used and effective tunneling technology in various rock mass quality circumstances. A “faulted rock mass” can range from a highly fractured rock mass to a sheared weak rock mass, making the ground conditions challenging for tunneling, especially for TBMs. “Faulted rock” significantly affects hard rock TBMs, primarily due to the TBM’s high geological risk and poor flexibility. TBMs require careful planning and preparation, starting with preliminary assessments. This study investigates the impact of establishing an isolation material between a circular tunnel and the adjacent faulting rock on seismic response. The two parts of the parametric analysis for the isolation material utilized in the model look at how changes in the mechanical characteristics of the material, such as the shear modulus of the rock and the fault, affect the stresses created in the tunnel. The second section examines how changes in the isolation width concerning the fault width affect the stresses and displacements produced in the tunnel. Additionally, the effectiveness of isolating the tunnel during sudden changes in the characteristics of the rock was investigated under seismic loading perpendicular to the tunnel and parallel to the tunnel. The finite element approach was utilized to model the TBM tunnel and the neighboring rock with a fault or sudden change in the rock using Midas/GTS-NX, simulating the interactions between the rock and the tunnel. Time-history analysis using the El Centro earthquake was conducted to calculate the stresses in the tunnels during seismic events. Peak ground accelerations between 0.10 g and 0.30 g were utilized for excitation. A time step of 0.02 s and a length of 10 s for the seismic event were used in the analysis, with traditional grout pea gravel vs. the isolation layer. Comparisons were made between the absolute stresses (the greatest possible values) in the normal tunnel section (Sxx) and those induced in the tunnel with traditional grout and with isolation. Furthermore, the study of vertical displacement was taken into consideration. The seismic isolation method is highly effective in improving the seismic safety of bored tunnels. The results show that the significant values of the ratio between the shear modulus of isolation and the surrounding soil should be between 0.2% and 0.4%. Where parts of the tunnel run through a fault, the effective length of isolation should be between one and two times the fault width. The dynamic behavior of the tunnel with isolation is better than that with traditional grout. Generally, when isolation is used for any length, it reduces the stresses at the area of sudden change. Consequently, engineering assessments from both structural and geotechnical engineering viewpoints are now required for these unique constructions. An underground structure’s safety should be evaluated by the designer to ensure that it can sustain various applied loads, taking into account seismic loads in addition to construction and permanent static loads. Tunnels may be especially vulnerable in areas where the composition of the soil or rock varies.

Industrial waste-based Ni-catalysts for ammonia decomposition to produce clean hydrogen

The high mineral containing solid waste materials generated during aluminum production currently lacks any practical application. In this work, the potential of solid waste with/without additional nickel loading (10 to 20 wt%) was investigated as an active catalyst for low temperature ammonia decomposition to produce high purity hydrogen. The X-ray diffraction (XRD) analysis of the samples reveals that iron oxide was the primary component of solid waste with the ability to catalyze the ammonia decomposition reaction. The reducibility, metal support interaction and catalytic activity of the solid waste supported Ni-based catalysts were correlated by the reduction kinetics of the catalysts using temperature-programmed reduction (H2-TPR) data and nucleation/nuclei growth models. Based on the statistical indicators, it was concluded that the random nucleation model describes catalyst reduction adequately. The estimated activation energy for the reduction of the solid waste itself was significantly higher (108.5 kJ/mol) than that of solid waste supported catalyst containing 10 wt% Ni (86.6 kJ/mol). The increase in nickel loading also slightly decreased the activation energy of catalyst reduction, indicating an improvement in the reducibility of the nickel-containing catalysts. These reduction behaviors were also reflected in the ammonia decomposition reaction in a flow reactor. The addition of nickel onto the solid waste resulted in the creation of additional active nickel sites. Consequently, the nickel loaded solid waste supported catalysts exhibited significant improvements in ammonia decomposition activity. Among the three solid waste supported Ni-based catalysts, the catalyst containing 15 wt% Ni displayed the highest activity, that also remained unchanged over extended period, indicating the catalyst stability.

Fabrication of monolithic omniphobic PVDF membranes based on particle stacking structure for robust and efficient membrane distillation

Robust omniphobic membranes have attracted great attention in improving the continuous service performance of the membrane distillation (MD) in treating high salinity wastewater. However, the fabrication of omniphobic membranes commonly undergoes complex procedures of modification including the construction of rough structures and post-modification using low-surface-energy substances. Herein, monolithic omniphobic polyvinylidene fluoride (PVDF) membranes were conveniently constructed by the combination of porous membranes possess particle stacking structure generated by a one-step vapor-induced phase separation (VIPS) procedure with subsequent surface perfluorination modification. The water contact angle, soybean oil contact angle, and low-surface-tension ethanol contact angle of the perfluorinated modified membrane increased from 139.6°, 45°, and ∼0° of the original membrane to 153°, 141°, and 110°, respectively. In addition, the LEP of the perfluorinated membrane is as high as 0.32 MPa, which is higher than the 0.22 MPa of the original membrane. More importantly, the monolithic omniphobic membrane can maintain a stable water flux without deteriorating salt rejection rate during the entire MD testing due to its high specific surface area, high porosity, three-dimensional micro/nano hierarchical structure, and adjustable pore size. This study offers useful insights for constructing monolithic omniphobic membranes for efficient and robust MD processes without additional nanoparticle loading procedure.

Demand side management using optimization strategies for efficient electric vehicle load management in modern power grids.

The Electric Vehicle (EV) landscape has witnessed unprecedented growth in recent years. The integration of EVs into the grid has increased the demand for power while maintaining the grid's balance and efficiency. Demand Side Management (DSM) plays a pivotal role in this system, ensuring that the grid can accommodate the additional load demand without compromising stability or necessitating costly infrastructure upgrades. In this work, a DSM algorithm has been developed with appropriate objective functions and necessary constraints, including the EV load, distributed generation from Solar Photo Voltaic (PV), and Battery Energy Storage Systems. The objective functions are constructed using various optimization strategies, such as the Bat Optimization Algorithm (BOA), African Vulture Optimization (AVOA), Cuckoo Search Algorithm, Chaotic Harris Hawk Optimization (CHHO), Chaotic-based Interactive Autodidact School (CIAS) algorithm, and Slime Mould Algorithm (SMA). This algorithm-based DSM method is simulated using MATLAB/Simulink in different cases and loads, such as residential and Information Technology (IT) sector loads. The results show that the peak load has been reduced from 4.5 MW to 2.6 MW, and the minimum load has been raised from 0.5 MW to 1.2 MW, successfully reducing the gap between peak and low points. Additionally, the performance of each algorithm was compared in terms of the difference between peak and valley points, computation time, and convergence rate to achieve the best fitness value.

A Review paper on seismic response of various slab systems with and without lateral load resisting systems

With the ongoing modern trends of the construction industry, slab systems like flat slab and post tensioned slabs are widely used in the construction. Flat and post tensioned slab are widely favored by architects and clients for aesthetic reasons. They also do possess a huge advantage structurally over conventional slab arrangement such as Less depth of the slab is required , increasing the floor-to-floor height , longer spans are possible , no beam projections , reduced self-weight of the building and many more. But it comes with its own disadvantages as well such as Brittle punching (shear) failure. Which requires additional reinforcement along the connections of column and slab. Which increases the longitudinal steel required. Slab – column connections are the first point of yielding in higher seismic zones with buildings without lateral load resisting system (LLRS). In higher seismic zones the slabs can resist only the gravity loads and can’t resist the lateral dynamic loading and hence may require additional lateral load resisting system (LLRS) to resist lateral loads such as seismic and wind loads. Thus it becomes essential to study the seismic behavior of conventional slab , flat slab and post tensioned slab systems in high rise RCC structure with and without various LLRS ( lateral load resisting system).This study is aimed to study various literatures related to effects of lateral loads on flat and post tensioned slab system and different LLRS (lateral load resisting system) to make the structure more resistant and economical against such lateral loads considering parameters like story displacement , base shear , stiffness of the connections and time period.

Experimental study of moment redistribution in continuous concrete beams prestressed with unbonded tendons

AbstractThe moment redistribution in a continuous prestressed concrete beam occurs as a result of a change in the rigidity of a beam and formation of plastic hinges when approaching the failure. Rotation capacity is required to allow for moment redistribution. Four continuous two‐span concrete beams prestressed with unbonded tendons were built and loaded up to failure at the laboratory of Civil Engineering in Tampere University. The test beams had different reinforcement ratios in the support area when the degree of prestressing and amount of tension reinforcement in the midspans were kept constant. All test beams were loaded by bending, but one test beam had torsion load in addition to bending. The degree of bending moment redistribution was defined by using nonlinear analysis and equations from the European standard and ACI318, as well as the test results. Moment redistribution clearly occurred on all test beams, and the beams had a high level of deformability.

Effect of 2D/3D Visual and Haptic Cues for Fine Operation Tasks With Varying Difficulties

Fine operations exist in the form of teleoperation, human-machine cooperative work, and fine manual assembly. However, there is a lack of research that explores the characteristics of different assistive guidance methods and their use for fine operation tasks with different levels of difficulty. For this issue, this study first designed a prototype of a magnetic-based kinesthetic interaction device, and then using this device, a user study (n = 27) was designed and conducted. The experiment explored the performance of 2D and 3D visual cues as well as haptic cues when facing operation tasks with different levels of difficulty and analyzed the characteristics of each guidance modality and its reasons. The experimental results suggest that (1) visual cues are better suited than haptic cues to convey directional information in fine operations, (2) haptic cues can introduce an additional physical load, and (3) 2D visual cues’ missing depth information can affect operations in the view direction.

Effects of added trunk load on the in vivo kinematics of talocrural and subtalar joints during landing

BackgroundLanding from heights is a common movement for active-duty military personnel during training. And the additional load they carry while performing these tasks can affect the kinetics and ankle kinematic of the landing. Traditional motion capture techniques are limited in accurately capturing the in vivo kinematics of the talus. This study aims to investigate the effect of additional trunk load on the kinematics of the talocrural and subtalar joints during landing, using a dual fluoroscopic imaging system (DFIS). MethodsFourteen healthy male participants were recruited. Magnetic resonance imaging was performed on the right ankle of each participant to create three-dimensional (3D) models of the talus, tibia, and calcaneus. High-speed DFIS was used to capture the images of participants performing single-leg landing jumps from a height of 40 cm. A weighted vest was used to apply additional load, with a weight of 16 kg. Fluoroscopic images were acquired with or without additional loading condition. Kinematic data were obtained by importing the DFIS data and the 3D models in virtual environment software for 2D–3D registration. The kinematics and kinetics were compared between with or without additional loading conditions. ResultsDuring added trunk loading condition, the medial-lateral translation range of motion (ROM) at the talocrural joint significantly increased (p < 0.05). The subtalar joint showed more extension at 44–56 ms (p < 0.05) after contact. The subtalar joint was more eversion at 40–48 ms (p < 0.05) after contact under the added trunk load condition. The peak vertical ground reaction force (vGRF) significantly increased (p < 0.05). ConclusionsWith the added trunk load, there is a significant increase in peak vGRF during landing. The medial-lateral translation ROM of the talocrural joint increases. And the kinematics of the subtalar joint are affected. The observed biomechanical changes may be associated with the high incidence of stress fractures in training with added load.

Site-specific wake steering strategy for combined power enhancement and fatigue mitigation within wind farms

Wind energy plays a crucial role in the quest for sustainable energy solutions. However, optimizing the efficiency of wind energy utilization remains a significant challenge. Wake steering, a key strategy in the field, offers the potential to address this challenge. This study introduces an innovative site-specific wake steering framework that incorporates a wake superposition model for wake steering, a machine-learning based fatigue and power predictor and a multi-objective optimizer to both enhance total power generation and mitigate fatigue loads within wind farms. The wake superposition model, developed and validated here, successfully replicates secondary wake steering effects and provides a new solution for calculating superimposed transverse velocity. The study comprehensively considers and implements constraints based on physical laws. Analysis of inflow speed and turbulence levels reveals that wake steering can continue to enhance total power output. Power enhancement can reach up to 18% at lower turbulence levels and still achieve significant increases even when inflow speeds exceed rated values, with only marginal increases in fatigue loads. Lower turbulence levels improve optimization results at the expense of heightened structural loads, while higher turbulence levels lead to diminishing power enhancement and additional fatigue loads. Examination of wind turbine spacing shows that smaller intervals yield substantial power enhancement, with improvements of up to 51.7%, although the effect diminishes as intervals increase and wake recovery takes place. In conclusion, the proposed site-specific wake steering framework offers an efficient means of balancing enhanced wind farm power output and structural integrity, representing a significant advancement in wind energy optimization.

Analytical solution for buried pipeline deformation induced by normal and reverse fault considering structural joint influence

AbstractPrevious studies take less account of analytical solution analysis for buried pipeline under the action of active fault. Furthermore, current theoretical studies of fault‐pipeline interactions generally treat the structure as continuous pipeline, with less attention given to the effect of joints. This paper provides an analytical method to estimate the deformation and internal force of jointed pipelines under normal and reverse fault. By introducing the simplified soil deformation model and error function, the soil greenfield deformation curves under the influence of normal and reverse fault are obtained. Considering the interaction between the pipeline structure and the disturbed soil, the two‐parameter Pasternak foundation model is adopted to analyze the forces on pipeline infinitesimal elements. Then, the mechanical response of the jointed pipeline structure due to the fault additional load is solved by finite difference method. The accuracy of the presented analytical solution is verified by comparisons with observed data of model test and 3D numerical simulation results. Finally, the parametric analyses are performed to estimate the influence for the characteristics of the foundation, fault and joint, including subgrade shear stiffness, subgrade reaction coefficient, fault dip, joint rotational stiffness, joint spacing, and intersection of fault and pipeline.

Changes in gait parameters and pelvic movement during gait under the influence of light loads carried symmetrically or asymmetrically — preliminary research

Introduction: Walking is one of the basic human activities. Taking care of the correct gait pattern is important for maintaining proper body posture and preventing dysfunctions of the musculoskeletal system. Since walking often involves carrying a load, the study aimed to evaluate changes in gait parameters and pelvic movement during gait under the influence of light loads carried symmetrically or asymmetrically in a bag or backpack. Material and methods: The group of 11 women and 15 men aged between 19 and 25 were examined. The BTS G-Sensor device was used. The basic gait parameters were examined, as well as the symmetry coefficient of pelvic motion and the range of pelvic motion in each of the three planes. The test involving walking 30 meters was repeated four times: while walking without a load, with an additional load worn in a backpack on both shoulders, in a bag on the right shoulder, or in a bag worn diagonally on the left shoulder. Each time the load was equal to 10% of the participantʼs body weight. Results: Walking speed, stride length to body height ratio, gait symmetry coefficient, and left and right foot propulsive speed did not change significantly during walking while carrying a load of 10% of body weight, regardless of the method of carrying a bag or backpack. Conclusions: Although carrying a light bag or backpack does not change the basic gait parameters, even such a small load reduces the symmetry of pelvic movement and the range of pelvic motion in the frontal and transverse planes during walking.

Cognitive-Motor Dual-Task Performance of the Landing Error Scoring System.

The Landing Error Scoring System (LESS) is a common assessment used to determine biomechanical landing errors. However, this assessment is completed as a single motor task, which does not require additional attentional resources. It is unclear if the LESS can be used to detect cognitive-motor interference (i.e., dual-task cost) in biomechanical errors associated with lower extremity injury. To determine if the LESS is a suitable clinical assessment of dual-task performance in uninjured females and to evaluate whether specific landing criteria are more affected by an additional cognitive load than others. Observational Cross-Sectional Design. Setting: University research laboratory. Twenty uninjured, physically active females participated. Intervention(s): Participants performed the LESS under three different conditions: baseline landing with no cognitive distraction (Single), a visual-based dual-task (Visual), and a number-based dual-task (Number). Mean sagittal, frontal, and total LESS scores were compared between conditions using a one-way repeated measures analysis of variance with Tukey post hoc corrections. Cohen's d effect sizes with 95% confidence intervals were used to determine the magnitude of differences. The frequency of errors for each individual LESS item under the three conditions were compared using Chi-Squared analyses. Participants exhibited greater sagittal plane (P=.013, d=0.91 [0.26, 1.56]) and total (P=.008, d=1.03 [0.37, 1.69]) errors during the Visual condition compared to the Single condition. Frontal plane errors were significantly greater during the Number condition compared to the Single condition (P=.008, d=1.03 [0.37, 1.69]). The frequency of errors observed for each LESS item did not statistically differ between conditions (all P>.05). The LESS was able to detect a dual-task cost in landing errors during both the Visual and Number conditions. We recommend developing clinically-oriented solutions to incorporate similar dual- task paradigms in traditional injury risk reduction programs.

About the Use of Gearless Electric Motors in the Construction of an Exoskeleton Walking on an Uneven Surface

The regular walking (up or down) on a ladder (or an inclined plane) of a human operator with an exoskeleton of the lower extremities, carrying an additional load, is considered. It is assumed that the exoskeleton is equipped with high— torque electric motors without gearboxes — in the knee and, perhaps, in other joints. The modes of flat, single-support quasi-comfortable walking are considered, in the implementation of which both electric motors and a human operator with experience working with this mechanism participate. The nominal pattern of movement associated, in particular, with the circumvention of obstacles (steps) with a portable foot and placing it in the support position at the next step is set and supported by a person. The task of the algorithm controlling electric motors is to partially reduce the load that falls on the operator. From the point of view of minimizing human energy consumption, the supporting leg and especially its knee joint are the most important. In the knee joint of the supporting leg, an algorithm for controlling the corresponding electric motor is proposed, based on measuring the vertical reaction force of the support in combination, perhaps, with the angle in the knee and angular velocity. Feedback is constructed, the "successful" values of the coefficients of which can be predicted using a kind of least squares method along the nominal mode. The task of this feedback is actually the distribution of the load that falls to the share of the operator and the system of electric motors. It is shown by using numerical research methods to what benefits in terms of energy consumption in one regular step this can, in principle, lead. This principle of feedback construction extends further to the hip and ankle moments of the supporting leg. It is assumed that the portable leg is controlled everywhere only by the human operator’s own efforts, the absence of gearboxes allows this to be done without much friction loss, which in turn affects the smallness of energy costs and for the operator.

A Magnetron Using an Additional External Reactive Load for Frequency Tuning: Theory Features and Experiment

A Magnetron Using an Additional External Reactive Load for Frequency Tuning: Theory Features and Experiment

ESTABLISHMENT OF BASELINE CONDITIONS FOR TRICYCLE RESEARCH IN TUGUEGARAO CITY, PHILIPPINES

There are a lot of initiatives to reduce the effect of global warming. In the Philippines, in the sector of transportation, shifting to a modernized mode of transportation (EVs), development of mass transport, and the like are being pushed. However, the effectiveness of each solution cannot be quantified without established baseline information. The objective of this study is to provide baseline information on 2-stroke and 4-stroke tricycles in Tuguegarao City. Experimental test runs are conducted to determine the effect of the general terrain, weight, road gradient, and age on the mileage efficiency of the tricycles. For general mileage efficiency, ten 2-stroke and ten 4-stroke tricycles are deployed on the same routes. Results show that the average mileage efficiency of the 2-stroke is 23.4 km/L, while that of the 4-stroke tricycle is 31.77 km/L. On a flat road, an additional load of one (1) kg on the tricycles decreases the mileage efficiency by an average of 0.4131% and 0.4095% on the 2-stroke and 4-stroke tricycles, respectively. The 4-stroke tricycle is 30% more efficient when tested on inclined roads. There is no direct relationship between the age of the tricycles tested and their corresponding mileage efficiency. A representative drive cycle for each type of tricycle is developed using a microtrip-based cycle construction. A load cycle is also developed based on the representative drive cycles constructed. The results of this paper will be a good input for future transportation-related studies in the city. This could also be the basis of Local government unit (LGU) and other lawmaking bodies in drafting policies related to transportation and environment.

The collapsible nature of reworked residual granites in the Stellenbosch Municipality, South Africa

In South Africa, residual granite is associated with the collapse phenomenon, a geotechnical hazard that was first identified in the 1950s. Residual granite is a product of chemical weathering (in-situ decomposition) or physical weathering of the parent rock (granite) whilst reworked residual granites is defined as residual granite reworked in-situ by termites. Residual granite usually consists of bulky-sized quartz particles, with silts, and bridged by colloidal matter. Extreme leaching of the colloidal matter creates a structure like a honeycomb. It, however, leaves voids within the structure, which affects the mechanical behaviour of the soil. The soil collapses upon wetting under additional loading. Construction on soils with a collapsible fabric has led to many documented problems. This paper, therefore, reports on the examination of mineral composition and particle shape examination and its effect on behavioural changes of potentially collapsible soil. The soil used for this study includes reworked residual granite obtained from the Stellenbosch area in the Western Cape of South Africa. A multi-element analysis and morphological studies were performed on mounts using the ZEISS EVO MA15 scanning electron microscope at the Centre for Analytical Facility at Stellenbosch University. Shape analysis confirmed that the severity of collapse increased with increasing angularity. In addition, the type and amount of clay present at particle contacts influenced the swell and collapse behaviour of reworked residual granite.

Dynamic Structural Change of Plant Epidermal Cell Walls under Strain.

The molecular foundations of epidermal cell wall mechanics are critical for understanding structure-function relationships of primary cell walls in plants and facilitating the design of bioinspired materials. To uncover the molecular mechanisms regulating the high extensibility and strength of the cell wall, the onion epidermal wall is stretched uniaxially to various strains and cell wall structures from mesoscale to atomic scale are characterized. Upon longitudinal stretching to high strain, epidermal walls contract in the transverse direction, resulting in a reduced area. Atomic force microscopy shows that cellulose microfibrils exhibit orientation-dependent rearrangements at high strains: longitudinal microfibrils are straightened out and become highly ordered, while transverse microfibrils curve and kink. Small-angle X-ray scattering detects a 7.4nm spacing aligned along the stretch direction at high strain, which is attributed to distances between individual cellulose microfibrils. Furthermore, wide-angle X-ray scattering reveals a widening of (004) lattice spacing and contraction of (200) lattice spacing in longitudinally aligned cellulose microfibrils at high strain, which implies longitudinal stretching of the cellulose crystal. These findings provide molecular insights into the ability of the wall to bear additional load after yielding: the aggregation of longitudinal microfibrils impedes sliding and enables further stretching of the cellulose to bear increased loads.

Nanoparticulate TiN Loading to Promote Z-Scheme Water Splitting Using a Narrow-Bandgap Nonoxide-Based Photocatalyst Sheet.

Some oxide-based particulate photocatalyst sheets exhibit excellent activity during the water-splitting reaction. The replacement of oxide photocatalysts with narrow-bandgap photocatalysts based on nonoxides could provide the higher solar-to-hydrogen energy conversion efficiencies that are required for practical implementation. Unfortunately, the activity of nonoxide-based photocatalyst sheets is low in many cases, indicating the need for strategies to improve the quality of nonoxide photocatalysts and the charge transfer process. In this work, single-crystalline particulate SrTaO2N is studied as an oxygen evolution photocatalyst for photocatalyst sheets applied to Z-scheme water splitting, in combination with La5Ti2Cu0.9Ag0.1O7S5 and Au as the hydrogen evolution photocatalyst and conductive layer, respectively. The loading of SrTaO2N with CoOx provided increases activity during photocatalytic water oxidation, giving an apparent quantum yield of 15.7% at 420nm. A photocatalyst sheet incorporating CoOx-loaded SrTaO2N is also found to promote Z-scheme water splitting under visible light. Notably, the additional loading of nanoparticulate TiN on the CoOx-loaded SrTaO2N improves the water splitting activity by six times because the TiN promotes electron transfer from the SrTaO2N particles to the Au layer. This work demonstrates key concepts related to the improvement of nonoxide-based photocatalyst sheets based on facilitating the charge transfer process through appropriate surface modifications.

LSTM-based deformation forecasting for additional stress estimation of existing tunnel structure induced by adjacent shield tunneling

A redistribution of stress is caused by the excavation of a new tunnel within the soil surrounding the existing shield tunnel structure. This stress redistribution results in alterations to the soil and water loads around the existing tunnel structure, ultimately impacting its stress and deformation. The deformation response of existing tunnels is primarily focused on in most existing studies, with limited research conducted on the coupling system of new tunnel excavation, soil stress state, and deformation and stress of existing tunnels. This paper proposed an innovative methodology to predict deformation in existing tunnel structures and estimate additional stress during the excavation of a new shield tunnel. The reliability of the suggested calculation method was verified using measured internal force and convergence data of the structures. The results demonstrated that the Long Short-Term Memory (LSTM) model could more effectively establish the temporal correlation between the excavation parameters of new tunnels and the deformation of existing tunnels. Compared to the Recurrent Neural Network (RNN) model, the R2 of the LSTM model increased by 11.81% in the prediction of the tunnel waist and 9.38% in the prediction of the tunnel crown. The Light gradient boosting machine (LightGBM) algorithm was used to analyze the crucial factors of deformation of the existing tunnel structures during shield tunneling, and the results showed that the relative position and the average earth pressure were the essential factors. Furthermore, a calculation method for the additional stress of existing tunnel structures was proposed based on the load structure model. The method assumed that the additional load was distributed rectangularly at the top and bottom of the existing tunnel, and triangularly at the waist of the tunnel. The comparison between the calculated results and the measured results indicated that the phased characteristics of the internal force changes in the existing tunnel structure during the construction of a new tunnel could be accurately reflected by this method.