Cumulative Settlement Research Articles

Study on the Settlement and Deformation Characteristics of Surrounding Rock of Loess Tunnel

There is a water culvert with masonry structure in the mountain of Hanguguan Tunnel. Soil deformation caused by tunnel excavation leads to channel cracking. On the one hand, channel water infiltration leads to loess tunnel collapse, which can easily cause engineering accidents and delay the construction period. On the other hand, it will affect the channel water supply and cause social problems. In this paper, the spatial deformation of the tunnel excavation process in the loess layer is revealed through the settlement of the vault in the tunnel, the monitoring of the convergence of the perimeter, and the force monitoring of the lining support structure of the Hanguguan tunnel, and the influence of the tunnel excavation deformation on the culvert is revealed through numerical calculation. The results show that the arch at the tunnel exit has the largest settlement deformation, the larger cumulative settlement, and the faster settlement rate, and the deformation of the culvert is small, only a millimeter. Compared with the monitoring data, the numerical simulation of tunnel excavation and the vertical settlement are basically consistent with the actual situation.

Cyclic response of floating geosynthetic-encased steel slag columns in soft clay

Geosynthetic-encased stone column (GESC) technology for strengthening soft clay offers significant advantages in terms of cost-effectiveness, environmental sustainability, and engineering applicability. It is widely applied in treating soft foundations for railways, bridges, and embankments. This study evaluates the cyclic response of the geosynthetic-encased steel slag column (GESSC) composite foundation employing three-dimensional nonlinear finite element analysis. A numerical study is conducted to assess the cyclic response of floating GESSC considering the influence of key design variables, including cyclic load amplitude, loading frequency, geosynthetic encasement stiffness, and length-to-diameter ratio. Results show that both cyclic load amplitude and frequency affect the cumulative settlement and excess pore pressure within the GESSC foundation. Within specified limits, increasing the encasement stiffness and column length can significantly improve the GESSC load-bearing characteristics. The parametric study suggests an optimal geosynthetic encasement stiffness for the field prototype columns within the range of 4480–5760 kN/m and a critical steel slag column length of 10 times the column diameter.

Urban land subsidence monitoring and risk assessment using the point target based SBAS-InSAR method: a case study of Changsha City

ABSTRACT Changsha City is the political, economic and cultural centre of Hunan Province. In recent years, because of large-scale urban construction and special geological structure, land subsidence has become one of the main geological disasters in Changsha City, which seriously threatens the health of buildings and infrastructure. To solve this problem, this paper monitored the land subsidence in Changsha City from 2015 to 2021 using the Point Target (PT) based Small Baseline Subset InSAR (SBAS-InSAR), revealed the spatial distribution characteristics of land subsidence in the study area, studied the causes of subsidence, and carried out geological disaster risk assessment. The results show that the overall stability of Changsha City is dominated by uneven subsidence. The subsidence areas are mainly distributed in the north of Kaifu District, Moon Island, Malan Mountain Chuangzhi Park and the periphery of the main urban area. The maximum settlement rate is about 87 mm/year, and the cumulative settlement reaches 250 mm. The settlement monitoring results are basically consistent with the actual situation at the same time, which is mainly caused by engineering construction.

Experimental study on the dynamic behavior of a new medium–low-speed maglev subgrade structure

Constructing medium–low-speed magnetic levitation (MLS maglev) subgrade by borrowing the construction standards of high-speed railway (HSR) subgrade can result in enormous engineering waste because the amplitude, distribution width, and dynamic coefficient of the dynamic load of MLS maglev trains are much smaller than those of HSR trains. To address this problem, an innovative subgrade structure was proposed to match the dynamic loads of MLS maglev trains. Two experimental models are constructed to study the proposed MLS maglev subgrade at train speeds of 100 km/h, 120 km/h, 160 km/h, and 200 km/h. The two models are labeled as Models I and II, and the only difference between these two models is the type of surface layer material of the subgrade bed, whereas the other structural features are the same. Specifically, the Model Ⅰ employs graded gravel, whereas the Model Ⅱ uses A group filling. The experimental results indicate that for both models, the dynamic earth pressure amplitudes are all less than 20 % of the subgrade’s self-weight at the bottom surface of the subgrade bed. In addition, the cumulative settlement of the two models is below the cumulative settlement limit. Although both models with the proposed MLS maglev subgrade exhibit excellent long-term performance, the Model Ⅰ has superior attenuation characteristics of dynamic earth pressure, and smaller acceleration and dynamic deformation than that the Model Ⅰ. This is attributed to the graded gravel used in the Model Ⅰ, which possesses a greater dynamic modulus and damping ratio than the A group filling used in the Model Ⅱ. The results presented in this study could contribute to the comprehension of the dynamic behavior of the subgrade under the dynamic loads of MLS maglev trains. More importantly, compared to the existing MLS maglev subgrades, the proposed MLS maglev subgrade has lower construction standards and is thus suitable for practical engineering applications.

Risk assessment of land subsidence based on GIS in the Yongqiao area, Suzhou City, China.

This study focuses on the Yongqiao District in Suzhou City, Anhui Province, China, aiming to analyze the current situation of ground settlement and its influencing factors in the area. The selected risk indices include settlement rate, cumulative settlement amount, groundwater level drop funnel, thickness of loose sediment layer, thickness of soft soil layer, and the number of groundwater extraction layers. Additionally, vulnerability indices such as population density, building density, road traffic, and functional zoning are considered. An evaluation index system for assessing land Subsidence risk was established. The risk evaluation of land Subsidence was conducted using the Hierarchical analysis-composite index method and ArcGIS spatial analysis, The evaluation results show that the area of higher risk area is about 2.82 km2, accounting for 0.96% of the total area, mainly distributed in the area of Jiuli village, Sanba Street. The middle risk area is distributed around the higher area, with an area of about 9.18 km2, accounting for 3.13% of the total area. The lower risk areas were distributed in most of the study area, covering an area of 222.24 km2, accounting for 75.82% of the total area. The low risk assessment area is mainly distributed in Bianhe Street and part of Zhuxianzhuang Town, with an area of about 58.88 km2, accounting for 20.09% of the total area. The findings of this study are not only crucial for informing local policies and practices related to land use planning, infrastructure development, and emergency response but also enhance our understanding of the complexities of land Subsidence processes and their interactions with human activities, informing future research and practice in environmental risk assessment and management.

Analysis of sensor parameters for ultra close range lateral penetration of subway tunnel full section sand layer soil pressure shield tunneling

In order to solve the problem of large disturbance to the stratum caused by shield tunneling in the full face sand layer geology by using the earth pressure balance full bin tunneling technology in the subway tunnel shield construction, this paper presents a parameter analysis of the ultra close side penetration of the full face sand layer earth pressure shield in the subway tunnel. By analyzing the monitoring data of surface settlement caused by subway shield construction, it is concluded that the law of surface horizontal settlement basically conforms to peak settlement theory, and the law of surface vertical settlement basically shows a steady downward trend. Through the mathematical modeling of the cumulative settlement data affected by the shield passing of the right line tunnel at the surface monitoring point, the influence of the shield passing of the left line tunnel on the surface settlement is predicted, and the prediction result is accurate. The experimental results show that the maximum deviation is 1.47 mm and the minimum deviation is 0.03 mm. The prediction accuracy is high and meets the accuracy requirements of practical engineering. Under the same geological conditions and construction parameters, the disturbance law of tunnel shield construction on the ground surface has important guiding significance in practical engineering.

How to quantify the tunnel structural resilience in longitudinal direction: a discussion on the index and its effect

Shield tunnel is prone to longitudinal differential settlement due to the characteristics such as segmental linings and unpredictable changes in multiple uncertain environments. Excessive differential settlement may deteriorate the safety and operational serviceability of the shield tunnel. Resilience has been increasingly applied in structural performance assessment given that it can evaluate the ability of structure to absorb the disruption and to restore the performance level. However, the resilience index and analysis framework for tunnels are quite vague and still in the developing phase. In this paper, a resilience analysis framework is introduced, and the detailed model to quantify the resilience of shield tunnel is presented. The cumulative settlement, maximum, and average value of differential settlement are selected as the performance indexes, because they can reflect the ability of the tunnel to ensure the structural safety and meet the waterproof requirements of the circumferential joints. Then, the effects of these indexes are analyzed using a real case in Shanghai. The results show that the resilience grades calculated using the three performance indexes are different, and the cumulative settlement is regarded as the better index.

FAGSO-BP neural network model for settlement prediction of soft soil foundation

To address the problem of difficulty in theoretical formulas and numerical analysis methods to consider the prediction of foundation settlement in the case of multiparameter coupling, the fireworks algorithm (FWA) with a gravity search operator (FAGSO) is introduced into the back propagation (BP) neural network model, and the weight and threshold processes in the neural network are improved by the FAGSO algorithm. A soft soil foundation settlement prediction model based on a FWA optimized BP neural network (FAGSO-BP) with a gravity search operator is proposed. Based on the second phase of the soft foundation treatment project of the Shatian Port Area, Humen City, and Dongguan City, the parameters of pile load height, pore water pressure, and groundwater level were collected and tested. The results indicate that the average relative error of the predicted cumulative settlement value of the soft soil foundation was 0.06%, root mean square error was 7.68, mean absolute error was 4.30, mean absolute percentage error was 1.40%, and mean square error was 59.98. Compared with the BP neural network, GA-BP neural network, and FWA-BP neural network, the error was smaller and the model stability was higher.

Pre-and post-cyclic behavior of soft ground improved by geogrid-encased granular columns considering clogging effect

A triaxial apparatus was utilized to evaluate pre-and post-cyclic behavior of soft ground improved by geogrid-encased granular columns considering clogging effect. The pre-cyclic behavior of specimens showed that the deformation modulus improvement due to the use of a stiffer encasement would be less noticeable in case of clogged granular columns. It was found that during cyclic loading, the use of geogrid encasement will be effective in reducing cumulative settlements and mitigating the liquefaction potential when its tensile stiffness is large enough. Moreover, the post-cyclic behavior of specimens showed that the use of granular columns (whether encased or non-encased) decreased the dependence of the ground deformation modulus on the CSR changes so that the evaluation of the cyclic-induced ground deformation can be done completely independent of the cyclic loading magnitude. It was also found that the use of an encasement with appropriate stiffness played an important role in minimizing the loss of the strength of the ground stabilized by granular columns after experiencing cyclic loads, especially under large earthquakes and after the occurrence of possible liquefaction.

Experiment on the performance of high-speed railway subgrade with tire debris mixed filling

As an important component of railway track, railway subgrade bears a huge dynamic load from trains. To explore the feasibility and dynamic characteristics of mixed filling of railway subgrade soil with tire debris, a series of large-scale indoor model tests were conducted to compare and analyse the magnitude and distribution of earth pressure, and the cumulative settlement displacement of sleepers, under two different loading conditions (i.e., single-stage cyclic loading and multi-stage cyclic loading). The results demonstrate that under all conditions, the vertical displacement at the sleeper ends is greater than that at the sleeper middle, the vertical displacement at the sleeper end decreases with the increase of static load and frequency, but increases with the increase of amplitude. Additionally, adding tire debris can help reduce the settlement and displacement of the subgrade soil, and the same amount of tire debris has the best effect when mixed in two layers. Moreover, multi-stage cyclic loading can significantly reduce the cumulative settlement of the subgrade soil. Under multi-stage cyclic loading, the settlement displacement at the end of the subgrade soil sleeper is larger than that at the middle of the sleeper, but the difference gradually decreases as the static load increases. It is revealed from the research that tire debris can significantly improve the performance of railway subgrade soil.

Evolving support vector regression based on improved grey wolf optimization for predicting settlement during construction of high-filled roadbed

The reconstruction and expansion of highways have become the dominant focus of current infrastructure development. However, this process often results in significant differential settlement between the new and old roadbed, leading to various pavement issues. Machine learning methods undoubtedly provide a new approach for predicting roadbed settlement. However, most of the current research on predicting roadbed settlement focuses on post-construction settlement, and there is relatively little involvement in predicting settlement during roadbed filling. Therefore, it is necessary to accurately predict the settlement during the roadbed construction period. This study establishes an improved settlement prediction model for roadbed construction using a combination of differential evolution (DE), grey wolf optimization (GWO), and support vector regression (SVR). The model incorporates cumulative filling time, cumulative filling height, and daily rainfall as input parameters, while the corresponding cumulative settlement serves as the output. To evaluate the effectiveness of the proposed DE-GWO-SVR model, the training set consists of two weeks' data of sample data, while the latter week's data is used as the test set to predict settlement. Meanwhile, the predictive performance is assessed using various evaluation metrics. The coefficients of determination (R2) for the settlement prediction results were all higher than 0.95. The findings indicate that the settlement predictions made by the model align well with the measured values. Moreover, the conventional SVR and artificial neural network (ANN) models for predicting roadbed settlement have been established. The R2 for the conventional SVR model is 0.7793, while that for the DE-GWO-SVR model is 0.9977. The results demonstrate that the optimized DE-GWO-SVR model outperforms the conventional approaches across all evaluation criteria. This affirms the high prediction accuracy and strong generalization ability of the established DE-GWO-SVR settlement prediction model. Therefore, the DE-GWO-SVR settlement prediction model can realize high-precision prediction of settlement during roadbed construction. This is conducive to the timely adjustment of the filling scheme during the roadbed construction to ensure the safety and stability of the high-filled roadbed.

Rheological consolidation analysis of saturated clay ground under cyclic loading based on the fractional order Kelvin model

AbstractBased on Biot porous medium theory, considering the coupled reaction of soil skeleton rheology and pore pressure dissipation, the present work investigates the dynamic consolidation characteristics of saturated clay ground under cyclic loading. First, the rheological behavior of the soil skeleton was described by the fractional order Kelvin model. The dynamic consolidation governing equations for the saturated clay were established theoretically in a three‐dimensional axisymmetric coordinate system. Second, the transform domain analytical solution of the dynamic consolidation of saturated clay was obtained using the Hankel–Laplace coupled transform method, and the solution in the time–space domain was further obtained through numerical inversion. Finally, the rheological consolidation behavior of saturated clay under cyclic loading and the influences of parameters were analyzed. The results show that the rheology of the soil skeleton had an inhibitory effect on pore water permeability; compared with elastic skeleton soil, the rheological clay had a slower settlement rate in the primary consolidation stage, a faster rate in the secondary consolidation stage, and greater long‐term settlement. In addition, under cyclic loading, the pore pressure response in saturated clay lags behind the effective stress, and a larger viscous order is associated with faster development of cumulative settlement.

Surface Subsidence over a Coastal City Using SBAS-InSAR with Sentinel-1A Data: A Case of Nansha District, China

The loss of life and property in economically developed areas due to geological hazards caused by intense ground subsidence is incalculable. As one of the fastest growing areas in the Guangdong-Hong Kong-Macao Greater Bay Area, the study of ground subsidence in Nansha will help to provide a scientific basis for urban planning and improve the capacity of monitoring and prevention of ground subsidence. The combination of coastal soft soil foundation and urbanization conditions creates a certain risk of land subsidence. We chose Nansha District, the geographical center of the Greater Bay Area, as the study area to analyze its surface subsidence characteristics in recent years. The 20-view Sentinel-1A data and SBAS-InSAR technique were used to monitor the ground subsidence in Nansha from 2017 to 2023. The main rate of ground subsidence in Nansha ranges from −19.4 to 7.7 mm/yr and is distributed in the urban area, along the rivers, in the construction area, and in the reclamation area. As of 4 May 2023, the average ground settlement in Nansha is 10.05 mm and the maximum settlement can be up to 142.45 mm. The 6-year total settlement at all four settlement intensities is greater than 60 mm, with the highest value exceeding 110 mm. The cumulative settlement increases with time, but inverse settlement and no settlement also occur at points where settlement is severe. For settlement caused by soft soil consolidation, it is recommended that drainage pipes be installed to accelerate drainage as a means of stabilizing settlement. For settlement caused by groundwater extraction and additional loads on the road surface, it is recommended to rationally extract groundwater and reinforce the foundation of the road surface with severe settlement.

Deformation Pattern and Failure Mechanism of Railway Embankment Caused by Lake Water Fluctuation Using Earth Observation and On-Site Monitoring Techniques

The prediction of railway embankment failure is still a global challenge for the railway industry due to the complexity of embankment failure mechanisms. In this work, the pre-failure deformation and the settlement from abnormal deformation to the final failure were investigated based on earth observation and on-site monitoring with a focus on the deformation stage and failure mechanism of railway embankments. Some new viewpoints are suggested: (1) the differential settlement of ~19 mm revealed via InSAR at the failure region of the embankment may have been caused by internal erosion after rapid drawdown. The cumulative settlement was found to increase with the decline of the lake water level. (2) The railway embankment experienced three phases of primary, secondary, and accelerated creep phases, similar to the evolution of most landslide or dam failures. However, the train loading and seepage force may have aggravated the secondary consolidation, promoting the embankment to enter the accelerated creep phase quickly. The deformation pattern was presented as an exponential curve trend. (3) The formation mechanism of embankment collapse can be summarized as “seepage failure-creep-shear slip-collapse” failure under repeated train loading and rapid drawdown. This work provides some clues for early warnings and for the development of maintenance plans.

A centrifuge study into the installation response of steel, open-ended, tubular piles, dynamically driven using prolonged impulses

A centrifuge study into the installation response of steel, open-ended, tubular piles, dynamically driven using prolonged impulses

Probabilistic assessment of high-speed vehicle-induced cumulative settlement of railway soft soil subgrade based on direct probability integral method

Due to the variability of train loads, soil properties, and other factors, the cumulative settlement of high-speed railway soft soil subgrade induced by cyclic trains holds strong randomness and evolutionary characteristics. Thus, the prediction of cumulative settlement and assessment of the subgrade status is important to ensure the safety of high-speed trains. For this purpose, a vehicle-track-subgrade interaction model is established for calculating the dynamic stresses of the subgrade, and then the cumulative settlement and its evolution characteristics are predicted. Furthermore, the direct probability integral method (DPIM) is introduced to implement the uncertainty quantification and reliability assessment of cumulative settlement, especially spatial distribution, 3D-probability density function and the variation of reliability index with load cycles. A comparison between Monte Carlo method and DPIM is performed to demonstrate the accuracy and efficiency of stochastic analysis with respect to cumulative settlement. The sensitivity and reliability assessment of the cumulative settlement under the cases of different speed, train load and soil strength are investigated by numerical examples to illustrate the robustness of the proposed method. The results show that cumulative settlement is most sensitive to soil strength, followed by train axle loads. Besides, a reliability assessment method proposed in this work, which considers cumulative settlement, provides guidance for the design and maintenance of subgrade in this paper.

Axial cyclic performance of a jacked pile in structured clays: A semi-analytical solution approach

Cyclic loads resulting from environmental factors such as wind, waves, trains, and construction activities pose a potential hazard to the stability of piled structures. These loads can cause the performance degradation of piles, including cumulative settlement and weakening of bearing capacity. This paper presents a semi-analytical solution for evaluating the axial cyclic behavior of jacked piles in structured clays. The solution employs enhanced nonlinear load-transfer models that effectively capture the stress-strain hysteresis and interfacial cyclic degradation characteristics. The key factors influencing pile behaviors are incorporated within the analytical approach, encompassing pile installation, subsequent soil equalization, and the static and cyclic loading encountered during service. The validity of the current solution is established through model pile tests conducted in artificially structured clays under static and cyclic loading conditions. Extensive parameter studies are performed using the proven theoretical approach to emphasize the influence of soil structure and cyclic loading on pile behavior. The results demonstrate a favorable agreement between the theoretical and measured values in static and cyclic pile response analyses. Compared with the response of jacked piles in reconstituted clays, the pile response in structured clays with a cement content of Aw = 4%, including penetration resistance, final ultimate bearing capacity, and the convergence speed of permanent settlement, has been substantially improved. The parameter studies indicate that soil structure and cyclic loading patterns significantly influence the axial cyclic performance of jacked piles in natural clays.

Importance of Aquitard Response Time for Groundwater Management in Multi-Aquifer Systems Subject to Land Subsidence

Groundwater management models have been widely applied to obtain optimal pumping strategies for land subsidence control, but most of them do not explicitly incorporate land subsidence variables (such as cumulative settlement and land subsidence rates) within the model constraints and neglect the transient effect due to aquitard storage. Here, three operating scenarios of a hypothetical multi-aquifer system, which include a highly compressible aquitard, were implemented with the aim of evaluating land subsidence and identifying management schemes with the support of an optimization model for groundwater management. In a 50-year management period, maximizing pumping while restricting drawdown to 10 m after year 25 stabilizes groundwater levels within the aquifer, but land subsidence continues to reach 4.8 m at year 50. The effect of reducing pumping rates and how early in the management period this is implemented is also analyzed. Restricting the pumping rate as early as year 6 leads to reduced land subsidence at year 50 by 17%. If pumping reduction is delayed, larger land subsidence rates occurred in the system (7.9, 8.3 and 9.6 cm/year in the tested cases); however, if the total settlement is evaluated as a proportion of the thickness of the aquitard, values of the order of 10% are presented. Our results highlight the importance of timely decisions for groundwater management based on the response time of the aquitards in multi-aquifer systems.

Model test on thermo-mechanical properties of static drill rooted energy pile under long-term temperature cycles

Static drill rooted (SDR) pile emerges as a composite of a prefabricated pile and cemented soil. SDR pile technology was introduced into the energy pile design due to its high load-bearing capacity, excellent heat transfer performance and favorable stability. Indoor model tests were established to investigate the thermo-mechanical behavior of an SDR energy pile under long-term temperature cycles. It was found that the studied pile had better heat transfer performance and bearing capacity (50%) than the ordinary pile. After twenty long-term temperature cycles, Additional tensile and compressive stress were observed in the pile. The additional thermal stress in the pile initially increased and then decreased with the increasing depth of the pile. The stress fluctuation would not damage the pile material since it was maintained within the design value of concrete strength. The side friction of the pile gradually increased with the increasing cycle numbers. The cumulative settlement of the SDR energy pile was induced by temperature cycles and reached −0.155 mm (0.18% D) after 20 cycles, less than the ordinary pile. The first two cycles accounted for 53% of the total cumulative settlement, and cooling was the main factor causing pile top settlement. The ultimate bearing capacity of the SDR energy pile was decreased by 9% after 20 cycles. The investigation of the long-term thermo-mechanical behavior of the SDR energy pile provides a theoretical basis for its practical application. SDR energy piles are significant for the efficient use of shallow geothermal energy.

Long-term settlement of metro viaduct piers: A case study in Shanghai soft soil

This study aims to investigate the long-term settlement behavior of metro viaduct piers in soft soil in Shanghai. Field monitoring was conducted for eight years, from the official opening until 2021. The results indicate that the settlement rate of the majority of piers was higher in the initial years and gradually reduced since 2017. Up to 2021, the maximum cumulative settlement St was 15.9 mm, which accounted for 0.8 times the limit of St (Ut). Seven settlement troughs were observed during the monitoring period. Muddy soil and nearby rivers significantly influenced the long-term pier settlements. St decreased proportionally with the thickness of the muddy soil. Piers located near the river experienced higher settlements than those located farther away, with a maximum settlement difference of 0.28–0.42 Ut. The influence of the river on St extended up to a range of 3–4 times the width of the river (Wr). Additionally, there were noticeable differences in settlement between piers constructed with tubular piles and those constructed with bored piles, particularly during the first two years after completion. Under similar conditions, the St of piers with tubular piles were 0.28 Ut (5.5 mm) larger than those of piers with bored piles on average. In addition, the slope k between the excavation-induced pier settlement and the ratio of the excavation depth to the distance was closely related to the type of retaining structure. The ratio of k values for the pit wall soil reinforcement, row piles and diaphragm wall was approximately 4:2:1. To prevent excessive pier settlement under similar geological conditions, it is recommended to employ a more rigid retaining structure and avoid using a soil-reinforced enclosure for pit walls.