Maximum Horizontal Displacement Research Articles

Study on the Bouncing Process Induced by Ice Shedding on Overhead Conductors under Strong Wind Conditions

Strong winds can lead to more complex ice shedding oscillation processes for overhead conductors, inducing flashovers, strand breakages and other accidents. This study analyzes the aerodynamic parameters of several typical icing features and establishes a numerical model for ice shedding on overhead conductors under strong wind conditions. The results show that for the same amount of icing, the resistance and lift force on the conductor changes with ice shape, wind attack angle and wind speed, which has a significant effect on the ice shedding jumping process. When the wind attack angle approaches 180°, the airflow resistance of the fan-shaped and D-shaped icing conductors significantly increases. And in the process of ice shedding response of transmission lines, the lateral amplitude may exceed 20 m, which increase the discharge risk of horizontally arranged conductors. Moreover, for the significant lateral oscillation of conductors by ice shedding under strong wind, the maximum horizontal displacement is approximately 1.6 times the difference in lateral position before and after ice shedding.

Effect of assembled H-shaped steel struts with servo system on the safe excavation of a subway station

An innovative design of assembled H-shaped steel struts (AHSS) with servo system is introduced for the deep excavation of a T-shaped subway interchange station in soft soil. Analysis of the field monitored axial force of the strut, horizontal displacement of retaining wall, ground surface settlement and displacement of the nearby existing tunnel showed that the servo system could provide a convincing stable axial force for each level of AHSS. When a new level of AHSS with servo system was put into operation, the axial force of the closest level of concrete strut above tended to be more greatly affected than the other levels of strut. The first level of concrete strut contributed much less to resisting horizontal displacement of the diaphragm wall than the other levels of strut, and was under tension during the later stage of excavation. The maximum horizontal displacement of diaphragm wall, displacement of the existing tunnel and ground surface settlement were all controlled well with the operation of AHSS with servo system. Meanwhile, stricter control of the horizontal displacement of the diaphragm wall in the early stage is considered to be beneficial to the control of further deformation of the excavation at a later stage.

Deformation of Existing Shield Tunnel Adjacent to Deep Excavations: Simulation and Monitoring Analysis

Deep excavations near subway tunnels can induce deformation, necessitating a comprehensive investigation into causal factors and mitigation strategies. Field measurements were conducted to assess both vertical and horizontal displacements of existing tunnels near a deep excavation in Shenzhen. Utilizing a validated three-dimensional finite element model that considers structure−strata interactions, this study analyzes tunnel displacements, ground movements, diaphragm wall impacts and the sensitivity of enclosure structure parameters. The results indicate that tunnel deformation correlates with enclosure structure deformation, particularly near the center of the pit. Moreover, shallow soil excavation significantly affects the vertical displacement of shallow-buried tunnels. However, the design parameters of the existing enclosure structures inadequately limit tunnel displacement. Therefore, it is crucial to intensify vertical displacement monitoring in shallow tunnels during early excavation stages and to enhance horizontal displacement monitoring during later phases. Implementing measures such as optimizing central support design or retaining soil at the pit bottom helps control maximum horizontal displacement. While support stiffness plays a greater role than retaining wall thickness, its impact on deep excavation projects is limited.

Numerical Simulation and Deformation Prediction of Deep Pit Based on PSO-BP Neural Network Inversion of Soil Parameters.

The finite element numerical simulation results of deep pit deformation are greatly influenced by soil layer parameters, which are crucial in determining the accuracy of deformation prediction results. This study employs the orthogonal experimental design to determine the combinations of various soil layer parameters in deep pits. Displacement values at specific measurement points were calculated using PLAXIS 3D under these varying parameter combinations to generate training samples. The nonlinear mapping ability of the Back Propagation (BP) neural network and Particle Swarm Optimization (PSO) were used for sample global optimization. Combining these with actual onsite measurements, we inversely calculate soil layer parameter values to update the input parameters for PLAXIS 3D. This allows us to conduct dynamic deformation prediction studies throughout the entire excavation process of deep pits. The results indicate that the use of the PSO-BP neural network for inverting soil layer parameters effectively enhances the convergence speed of the BP neural network model and avoids the issue of easily falling into local optimal solutions. The use of PLAXIS 3D to simulate the excavation process of the pit accurately reflects the dynamic changes in the displacement of the retaining structure, and the numerical simulation results show good agreement with the measured values. By updating the model parameters in real-time and calculating the pile displacement under different working conditions, the absolute errors between the measured and simulated values of pile top vertical displacement and pile body maximum horizontal displacement can be effectively reduced. This suggests that inverting soil layer parameters using measured values from working conditions is a feasible method for dynamically predicting the excavation process of the pit. The research results have some reference value for the selection of soil layer parameters in similar areas.

Mechanical Properties of Super-large and Shallow-buried Loess Tunnel with the Prefabricated Temporary Support

Background: At present, there are few studies on the mechanical properties of tunnels with prefabricated temporary support. Based on the project of the Xichengshan Tunnel on the highway from Zhuanglang to Tianshui, this paper studies the mechanical properties of tunnels with prefabricated temporary support The utility model patent for this article is a temporary steel support device for loess tunnel excavation. The patent number is ZL 2022 2 0141276. 1. Objective: The study aims to show the mechanical properties of a super large section of prefabricated temporary support shallow tunnel. Methods: The mechanical properties of the tunnel surrounding rock, lining, steel arch, anchor, and temporary support during construction were analyzed by combining numerical simulation and theoretical analysis. The maximum and minimum stresses of the tunnel surrounding rock, lining, steel arch, and anchor, and the maximum and minimum displacements of prefabricated temporary support were found through the analysis results. Results: The stress and displacement fields of surrounding rock, lining, steel arch, bolt, and temporary support of loess tunnel were analyzed. Results showed that the maximum principal stress of the surrounding rock is 0.293MPa, and the maximum horizontal displacement is 0.359cm. The maximum horizontal displacement of the lining is 0.413cm, the maximum vertical displacement of the steel arch is 1.538 cm, and the maximum displacement of the temporary support structure is 1.459 cm. The above data verify the safety of the proposed combined temporary support structure. Conclusion: Through the analysis results, the maximum and minimum stresses of the tunnel surrounding rock, lining, steel arch, and anchor, and the maximum and minimum displacements of assembled temporary support are found, which can guide subsequent construction.

Protective effects of measures for railway subgrade adjacent to excavation of a parallel pit

The Hongqiao Airport–Pudong Airport urban railway construction project in Shanghai, includes a 156.1-m-long deep strip foundation pit that runs closely parallel to the subgrade of the Shanghai–Hangzhou High-speed Railway, operating at 300 km/h. With a maximum excavation depth of 25.5 m and a minimum distance of only 10.6 m between the outer edge of the pit and the subgrade slope foot, controlling the deformation of the foundation pit in soft soil and ensuring the safe operation of the adjacent high-speed railway present significant challenges. Various protective measures were implemented to mitigate subgrade deformation caused by pit excavation, including partition excavations, 1.5-m-thick diaphragm walls, a servo steel strut system, isolation piles between the subgrade and diaphragm walls, and water-resistant barriers. The foundation pit, soil, and railway subgrade deformations during excavation were measured and analysed. The results demonstrate that the protective measures limited lateral diaphragm wall deformation to within 0.14% of the excavation depth. The maximum horizontal and vertical displacements of the subgrade caused by excavation were 3.2 mm and 1.5 mm, respectively. As a result, trains safely passed through this section at a limited speed of 120 km/h. The findings presented provide useful reference information for similar projects.

Instability evolution of expansive soil slope due to short duration-varying intensities of rainfall

This study examines the evolution of instability in induced expansive soil slopes under varying rainfall intensities. The destabilization evolution of expansive soil slopes and their stability under three different rainfall intensities were revealed through indoor modelling and numerical simulation. The findings indicate that slopes are not destabilized by short duration and low rainfall intensity alone. Slope failure under strong rainfall intensity follows a three-stage evolutionary process. As rainfall intensity increases, the slope's water content, soil pressure, and pore water pressure increase. However, the stress at each monitoring point of the slope affected by rainfall follows a different pattern. Under low rainfall intensity, the water content of the slope surface is higher than that of the slope foot. Under strong rainfall conditions, the water content of the slope foot is higher than that of the slope surface. Therefore, it is important to implement seepage prevention measures on the slope surface and drainage measures on the slope foot to ensure slope stability. Rainfall affects the soil pressure at each monitoring point of the slope, causing unloading on the slope surface and fluctuation at the foot of the slope. This phenomenon becomes more pronounced with increasing rainfall intensity. Numerical simulation confirms that the overall horizontal displacement distance of the slope increases with rainfall intensity, but the horizontal displacement range becomes shallower. The slope's maximum horizontal displacement occurs at its foot, with values of 0.29 m and 0.34 m under moderate and heavy rainfall, respectively, representing a growth rate of 17 %. Settlement of the slope under different rainfall intensities was greatest at the top of the slope area. The lateral stresses generated by the settlement resulted in soil uplift at the leading edge of the slope.

Numerical Simulation of Double-Row Retaining System with Different Piers

With the rapid expansion of foundation pit excavation areas due to the burgeoning underground transportation networks in large cities, spatial combined double-row retaining structures have become indispensable for ensuring stability and minimizing deformation. Integrating piers into these structures enhances stiffness; however, the research on this topic is limited. This study investigates the Chisha Metro project, which utilizes a double-row support structure with added support piers to improve overall stiffness. Numerical simulations are employed to model the foundation pit and analyze the stress distribution and deformation of double-row retaining systems with T-shaped, cross-shaped, or square-shaped piers. The results demonstrate that the retaining system, after the introduction of piers, exhibits reduced maximum horizontal displacement and surface settlement of soil, and indicates spatial characteristics and the transformation from a planar problem to a spatial problem. Furthermore, in specific geological conditions, the T-shaped support pier proves to be more effective in connecting the front and rear support structures compared to the cross-shaped and square-shaped support piers, which mainly reinforce the soil without connecting the support structures. This research provides valuable insights for improving design and construction practices in foundation pit engineering.

Seismic Response of Vertical Hybrid Concrete/Steel Frames Considering Soil–Structure Interaction

The aim of this study is to investigate the seismic behavior of concrete/steel mixed structures. In engineering praxis, many buildings consist of two parts: one made of reinforced concrete and the other made of steel. There are several difficulties in the code-based seismic design of these structures due to the different dynamic responses of each discrete part. Seismic design codes, such as the IBC and Eurocode 8, do not provide instructions for structures consisting of two parts. In addition, they use a single-loading scenario, but there are many locations that are affected by more than one earthquake in a short period. Another drawback is that recent provisions do not consider soil–structure interaction effects. The specific issue addressed here is the seismic response of mixed structures, which is evaluated through inelastic time–history analysis. More specifically, the response indices involve height-wise distributions for peak interstory drift ratios, maximum floor horizontal displacements, maximum floor accelerations, and plastic hinge formations in the frame elements when they are subjected to seismic sequences of earthquakes, as well as in far fault ground motions for different soil types. The results reveal that sequential ground motions lead to increased displacement demands, and they affect the permanent displacements. This phenomenon appears in both cases of stiff and flexible soil, as well as for both regular and irregular frames. It is found that soil–structure interaction generally leads to lower values of IDR, and maximum horizontal displacement and acceleration in comparison with the case of rigid soil assumptions.

Simulation test on shaft deformation induced by mining subsidence under similar gravity field in deep soil strata

Many shafts in China have experienced large deformations in the deep soil Strata, which has had a significant impact on mining safety. This study conducted a geotechnical model test called the seepage force model to address the deformation issues of shafts caused by mining solid mineral resources in regions with deep soil strata. This test simulated the impact of mining disturbance on shaft deformation within the soil section. The simulation utilized monitoring data from the model shaft, facilitating the determination of deflection displacements across different protection areas. The findings indicated a nearly linear relationship between the maximum horizontal displacement of the shaft and the mining coal seam thickness. The shaft protection areas within the soil section were reconfigured by modifying the movement angle from 45° to 37.6°. Consequently, the maximum horizontal displacements of the prototype shaft decreased to 73.8, 112.7, and 170.9 mm for mining coal thicknesses of 2.7, 5.3, and 8.0 m, respectively. These values represent 26%, 24.6%, and 26.7% reductions from the original design shaft displacements. When combined with the probability integral method, the simulation test results concerning the shaft protection rock pillars were exhaustively examined. This analysis paves the way for a more logical and reliable design approach for shaft protection rock pillars in areas characterized by deep soil and thin rock strata. The study findings hold immense significance in effectively mitigating and managing mining-induced subsidence disasters and ensuring the optimal design of shaft protection zones.

Ground settlement and estimation of maximum settlement value in adjacent foundation pit excavation

The excavation of adjacent pits following the initial foundation pit excavation can significantly influence ground settlement. Using a foundation pit excavation project in Changzhou as a prototype, this study employed the numerical simulation method in conjunction with the HSS model to analyze the settlement deformation characteristics of the original excavation and compare them with the recorded monitoring values. In this study, the analysis focused on the ground settlement between two pits by varying the spacing between them at different excavation depths. The findings revealed that the ground settlement does not exhibit a significant increase when the new pit is excavated at a shallow depth. However, it rapidly increases when the excavation depth of the new pit surpasses that of the existing pit. Furthermore, an increase in the distance between the two pits causes the maximum settlement position to shift towards the edge of the new pit. The maximum ground settlement is found to have a linear relationship with both the maximum horizontal displacement of the two pits and the spacing between them.

A Study on the Factors Influencing High Backfill Slope Reinforced with Anti-Slide Piles under Static Load Based on Numerical Simulation

Based on a real engineering case, this study employs the MIDAS finite element software to model the reinforced high embankment slope using anti-sliding piles. The accuracy of the finite element method is verified by comparing calculated outcomes with field monitoring data. Expanding on this foundation, an analysis of factors influencing the reinforced high embankment slope is undertaken to scrutinize the impact of diverse elements on the slope and ascertain the optimal reinforcement strategy. The results reveal the following: The principal displacement observed in the high embankment slope is a vertical settlement, which escalates with the backfill height. Notably, the highest settlement does not manifest at the summit of the initial slope; instead, it emerges close to the summits of the subsequent two slopes. However, the maximum horizontal displacement at the slope’s zenith diminishes as the fill height increases—a trend that aligns with both field observations and finite element computations. The examination of the influence of anti-sliding pile reinforcement on the high embankment slope unveils that factors like the length, diameter, spacing, and positioning of the anti-sliding piles exert minor impacts on vertical settlement, while variations in the parameters of the anti-sliding piles significantly affect the slope’s horizontal displacement. When using anti-sliding piles to reinforce multi-level high embankment slopes, factoring in the extent of horizontal displacement variation and potential cost savings, the optimal parameters for the anti-sliding piles are a length of 15 m, a diameter of 1.5 m, and a spacing of 2.5 m, presenting the most effective combination to ensure superior slope stability and support.

Deformation characteristics of existing tunnels induced by above-crossing quasi-rectangular shield tunnel

Quasi-rectangular shield (QRS) tunneling, a recent development in tunneling technology, offers the advantage of creating double tunnels with a single excavation. This technology causes significantly less secondary damage to the environment than traditional double shield tunneling. However, the deformation characteristics of existing tunnels caused by the QRS tunnel crossing above them are unknown. This study presents the first application of a QRS tunnel crossing above existing tunnels. It provides a comprehensive overview of the vertical displacement, horizontal displacement, segment convergence, and torsional deformation of existing tunnels when the QRS crosses above and runs parallel to the existing tunnels in the Hangzhou Metro Line 4. The measurement results indicate that the existing tunnels exhibit a maximum vertical displacement of 7.2 mm, maximum horizontal displacement of 2.3 mm, maximum segment convergence of 5.8 mm, and rotation index of up to ±10 × 10-4 at the intersection of the QRS and existing tunnels. All of the measurement results fall within the acceptable range, demonstrating the exceptional efficacy of QRS in controlling the deformations of existing tunnels. The effects of the plane position and distance between the tunnels on the deformation of the existing tunnels is also discussed. The deformation of the existing tunnels is negligible when the distance between the QRS and existing tunnels exceeds 16 m. The maximum vertical displacement, horizontal displacement, segment convergence, and zero-values of the rotation index occur at approximately 5 m in the plane position rather than at the intersection between the QRS and existing tunnels. The primary influence zone where the QRS tunnel crosses above existing tunnels is discussed.

Coupled SPH-FEM analysis of piled power transmission tower system subjected to debris flow

Debris flow is a type of highly dangerous geological hazard, which can pose significant threat to the safety of various infrastructures including power transmission tower system. However, the performance of piled power transmission tower system against debris flow has yet to be well investigated. A validated coupled SPH-FEM method was employed to investigate the behavior of a typical piled power transmission tower system subjected to various debris flows, accounting for influencing factors of slope angle, sliding distance, and density and thickness of debris flow. The findings revealed that the incorporation of power transmission tower was important to accurately estimate the impact force and horizontal displacement of the pile and the frontal piles undertook more than 70% of the total impact force; among the factors considered, the slope angle and density were found to be more influential. After examining the performance of existing prediction methods, two semi-empirical equations were proposed for respectively estimating the maximum impact force and horizontal displacement of pile based on multivariate regression analysis. Furthermore, it was found that debris flows did not likely cause steel tower to directly experience structural damages; however, its pile foundation could suffer moderate to severe damages depending on the debris flow conditions.

Slow slip event displacement on 2018 offshore Boso Peninsula detected by Sentinel-1 InSAR time-series analysis with numerical weather model assistance

SUMMARY The south-eastern offshore of the Boso Peninsula in Japan periodically experiences short-term slow slip events (SSEs) every few years. On 2018 June, an SSE occurred with the maximum surface horizontal displacement reaching up to 4.7 cm by according to the operational global navigation satellite system (GNSS) network. This study performed a time-series analysis of interferometric synthetic aperture radar (InSAR) with Sentinel-1 SAR images to investigate detailed spatial pattern of surface displacements caused by the SSE. With the assistance of an atmospheric delay correction with a regional numerical weather model output, the InSAR time-series analysis successfully captured displacement signals in three paths, whose maximum amplitudes in line-of-sight directions were 1.46, 1.86 and −0.80 cm. A checkerboard test revealed that the resolution of the slip inversion was higher when InSAR was used than that using GNSS, especially in and around the inland. The slip inversion with the actual displacement data derived from the InSAR time-series analysis was performed with the L-curve optimization, showing that the estimated slip area was concentrated offshore south-eastward from the Boso Peninsula with the maximum slip of 5 cm and the estimated moment magnitude of 6.4. As similar to previous SSEs in the Boso Peninsula, a seismic swarm simultaneously occurred in the downdip area adjacent to the estimated slip with the SSE occurrence, suggesting a different friction characteristics between them. This study demonstrates usefulnesses of the InSAR observation for capturing detailed spatial characteristics of small-displacement events like SSEs and of the hybrid use of the externally derived delay correction with the time-series analysis to improve the displacement detection accuracy.

Study on Numerical Simulation of Surrounding Rock Structure Safety of Urban Underwater Shield Tunnel: A Case in Chongqing

Based on the engineering background of shield construction of a subway section in Chongqing, which needs to pass through a park and there is a lake inside this park, this paper adopts theoretical analysis methods and numerical simulation calculation methods to explore the distribution law of the seepage field and the characteristics of water pressure in lining segments during shield tunneling. The results show that, during the whole excavation of a double-track tunnel with EPB shield, the maximum vertical effective stress is about 4.24 MPa, which is located at the arch foot of the tunnel. The maximum effective stress in the horizontal direction is about 3.61 MPa, which is located on both side walls of the tunnel in the horizontal direction; after the left and right tunnels are excavated in sequence, a “double precipitation funnel-shaped” pore pressure distribution is formed around the tunnel; during the construction of the shield tunnel, the vertical displacement and horizontal displacement of the surrounding rock show an increasing trend and gradually tend to be stable values of 24.09 mm and 25.28 mm; the segment vault has settlement, the maximum settlement is 21.8 mm, the arch bottom has uplift, and the maximum uplift is 24.4 mm. The maximum horizontal displacement of the segment appears on both sides of the arch waist, and the maximum horizontal displacement decreases with the increase of excavation steps; the positive bending moment of the lining segment is mainly distributed on both sides of the arch crown, and the negative bending moment is mainly distributed on both sides of the arch bottom. The axial force of the lining segment is compressive stress, and the maximum axial force is mainly distributed on both sides of the arch waist. The maximum normal shear stress occurs on both sides of the segment arch bottom. The study conclusions provide theoretical foundation and a new guidance for long-term safety evaluation of underwater tunnel structures.

Damage features and dynamic triggering mechanism of the Jianshanying landslide induced by underground mining in Shuicheng County, Guizhou Province, China

Extensive mining of mineral resources in the mountainous areas of southwestern China has caused frequent occurrences of landslides, threatening social and economic development. Therefore, further research on the formation mechanism of such landslides is urgently investigated. Using detailed geological investigations, a numerical simulation, and related theoretical analysis reveal the dynamic triggering mechanism, influencing factors, and mechanical evolution model of the Jianshanying landslide under the coupled action of heavy rainfall and mine blasting vibrations. Results showed the following: First, rainfall of about 5 days, which nearly saturated the slope, and nearly 3 blasting cycles (peak horizontal and vertical velocities of 0.3375 and 0.1573 cm/s, respectively) executed close to it were the main controlling factors inducing the landslide. Second, the macroscopic deformation of the slope manifested obvious subsidence and tipping, and the maximum vertical and horizontal displacements of the slope shoulder reached 13.466 and 2.961 m, respectively. Third, the critical failure of the slope occurred at 15 s in the dynamic analysis, and its subsequent responses involved disintegration and fragmentation, debris flow, scraping of the sliding bed, and self-stabilized accumulation. Finally, its mechanical evolution model was divided into the subsidence stage and the shear-tension stage. These results provide technical support for early identification and risk management of geological hazards in mines in southwestern China.

Study on Impoundment Deformation Characteristics and Crack of High Core Rockfill Dam Based on Inversion Parameters

In the numerical simulation of earth-rock dam, accurate and reliable mechanical parameters of the dam material are the important basis for dam deformation predictions and dam safety evaluations. Based on the deformation monitoring data of Luding core wall rockfill dam, the rheological parameters of rockfill and core wall materials are inverted in this paper. Combined with the actual filling and impoundment process of the dam, the numerical simulation is carried out, and the stress deformation and differential settlement of the dam after completion and impoundment are analyzed. The results showed that the stress deformation results of the dam based on the inversion parameters were in good agreement with the actual deformation. The horizontal displacement, settlement, and principal stress of the dam during the completion period were symmetrically distributed along the core wall. The maximum horizontal displacement occurred at the main dam on both sides of the core wall and the upstream and downstream dam slopes, and the maximum settlement occurred in the middle of the core wall. During the impoundment period, under the action of reservoir water pressure and upstream rockfill wetting deformation, the deformation and stress of the dam body no longer met the symmetrical distribution law, and the maximum horizontal displacement of the dam body during the impoundment period was located at 2/3 of the upstream dam slope. The maximum settlement of the dam body was located at 1/2 of the dam height. The maximum principal stress on the upstream side of the core wall was located on the left side of the bottom of the core wall, and the minimum principal stress was also located on the left side of the bottom of the core wall. The simulation results of the deformation and stress met the general law of earth-rock dam engineering. During the completion period, the deformation inclination of the dam crest was less than 1%. During the impoundment period, the deformation inclination of the dam crest area increased due to the wetting deformation of the upstream rockfill material. At the same time, the deformation inclination of the dam crest axis was larger than that of the upstream and downstream sides, and the deformation inclination of the dam crest at the middle of the valley was the largest, but it did not exceed 3%, that is, there would be no longitudinal cracks, which is consistent with the actual situation. The research results can better predict the stress deformation and crack of the dam body, and provide important support for dam safety evaluations.

Hydrology Drives Crustal Deformation and Modulates Seismicity in the Matese Massif (Italy)

Abstract We analyze the interplay between hydrology, deformation, and seismicity in the Matese massif, located in the Italian Southern Apennines. We find that this area is characterized by the concurrent action of two hydrologically driven processes: the first is the deformation detected by the Global Navigation Satellite Systems (GNSS) data in the shallowest part (above the elevation of the major springs) of the Earth crust, in phase with the hydrological forcing; the second is the triggering of seismicity at depth with a delay suggesting a downward diffusive process. We study the first process by applying a principal component analysis to the GNSS displacements time series, aiming to identify a common signal describing the largest data variance. We find that the maximum horizontal displacements associated with the first principal component (PC1) are larger than 1 cm in two GNSS sites, and the PC1 temporal evolution is well correlated and in phase with the flow of the largest spring of the region, which we consider as proxy of the water content of the massif. This suggests that the main source of horizontal deformation is the water content fluctuations in the shallow portion of the Matese aquifer, in particular within fractures located in correspondence of the main mapped faults. The deformation rates caused by this process are one order of magnitude larger than the tectonic ones. Finally, we infer the second process by observing the correlation between the background seismicity and the spring discharge with a time lag of 121 days. In our interpretation, downward diffusive processes, driven by aquifer water content variations, propagate pore-pressure waves that affect the fault’s strength favoring the occurrence of microearthquakes. This is supported by the values of hydraulic diffusivity (1.5 m2/s) and rock permeability (3.2–3.8×10−13 m2), which are compatible with what is observed in karstified limestones.

Multi-objective design and optimization of squeezed branch pile based on orthogonal test

In recent years, the emergence of the squeezed branch pile has presented a new avenue for civil engineering, offering a distinctive structure and favorable mechanical characteristics. Squeezed branch piles have strong compressive, uplift, and horizontal load resistance capabilities. Due to the existence of discs, the geometric parameters of squeezed branch piles are abundant but important. This article selects number of discs, disc diameter, disc squeeze angle, and disc spacing as the main influencing factors on the bearing capacity of squeezed branch piles and conducts a qualitative analysis of their mechanical properties. The aim of this article is to analyze the different bearing performances of squeezed branch piles through orthogonal experimental design, simulate test conditions using finite element software ABAQUS, obtain relevant data, and finally determine the weight ranking and optimal combination of influencing factors through range analysis to provide better guidance for engineering practices. Through multi-objective optimization design, six optimization objectives including compressive performance, compressive economic efficiency, uplift performance, uplift economic efficiency, maximum horizontal displacement and maximum bending moment of pile body were analyzed. The analysis methods used included comprehensive balance method, queue scoring method, principal component analysis method, entropy weight method, and analytic hierarchy process. The conclusions obtained are similar, and based on the judgment, the squeezed branch pile with 4 discs, disc diameter of 2.5D, disc squeeze angle of 35°, and disc spacing of 3D is considered as the optimal combination under consideration of all optimization objectives.