Soft Soil Research Articles

A numerical study of deep excavations adjacent to existing tunnels: Integrating CPTU and SDMT to calibrate soil constitutive model

Accurate determination of parameters for an advanced soil constitutive model highly relies on laboratory testing, even though it is notoriously difficult to obtain undisturbed samples for soft soils. This study explores the potential use of in-situ tests, such as piezocone penetration tests (CPTU) and seismic dilatometer tests (SDMT), to estimate the constitutive model parameters. Based on a case history of a deep excavation adjacent to existing tunnels in silt/sand-dominated sediments, a calibration approach of a set of the HSSmall (Hardening Soil Model with Small Strain Stiffness) model parameters is presented, and the derived parameters are used to numerically compute the interactive responses of tunnels and deep excavations. Several comparisons against field monitoring data indicate that the numerical model with the CPTU/SDMT-interpreted HSSmall model parameters adequately reproduces observed deformation responses of deep excavations adjacent to tunnels. However, the use of laboratory tests with disturbed samples to estimate the stiffness parameters of the HSSmall model may lead to an overconservative solution. This finding supports the use of CPTU/SDMT to provide representative parameters for a range of soil layers, leading to the conclusion that tunnel linings may be beneficial to mitigate ground movements and wall deflections due to a barrier effect.

Utilization of cement deep mixing pile for soft soil foundation: a malaysian case study

Cement deep mixing piles, as representatives of deep mixing technology, are mature and widely applied. However, effective application cases of cement deep mixing piles are relatively scarce in countries like Malaysia in Southeast Asia. In this paper, the application of cement deep mixing pile reinforcement in Malaysia is presented. Solidifying material was selected for deep mixing piles based on the soil conditions using unconfined compressive strength (UCS) tests. The relationship between the strength of deep mixing piles on-site and soil properties (type, organic matter content, and ion content) was analyzed. And a quality evaluation of the deep mixing piles in the project is conducted based on Kolmogorov-Smirnov (K-S) tests and relevant standards. Results show that fly ash cement is suitable as a solidifying agent for acidic soil layers containing organic matter in the local area. The strength of piles is significantly related to the soil condition. The UCS of cement mixing piles in silty clay and peat soils is smaller than clay. The overall correlation between organic matter content in the soil and UCS is negative, particularly when the organic matter content ranges from 10% to 14%, resulting in a significant drop in UCS. The bilateral significance probability is greater than 0.05 in K-S test, indicating that the UCS results in the projectconform to a normal distribution. Additionally, the evaluation of the overall quality of the mixing piles aligns with the requirements in the Japanese standard “Manual of Deep Mixing Construction Technology for Harbors and Airports” and the Chinese standard “Technical Code for Building Foundation Detection”.

An Effective Alternative to the Open Trench Method for Mitigating Ground-Borne Environmental Body Waves: Corrugated Cardboard Boxes Reinforced with Balsa Wood

This research develops and evaluates a recyclable corrugated cardboard vibration isolation box reinforced with balsa wood as an alternative to traditional open trench methods for mitigating ground-borne environmental body waves. This study includes designing and testing scaled prototypes, laboratory analyses, prototype fabrication, and full-scale field experiments. In soft ground conditions, ensuring slope stability during deep excavations is a key engineering challenge for open trenches. For this purpose, scaled prototypes were subjected to laboratory tests to assess the resistance of the wave barrier’s wall surface. Numerical analyses were also conducted to evaluate the strength of the internal lattice structure under various loads. A prototype was fabricated for on-site experiments simulating real-world conditions. Field experiments evaluated the vibration isolation performance of the proposed barrier. Accelerometer sensors were strategically placed to gather data, analyzing ground surface vibrations for free field motions to assess the vibration shielding efficiency of both the open trench method and the corrugated vibration isolation box, with and without Styrofoam infill. This study concludes that the recyclable corrugated vibration isolation box is a viable alternative, offering comparable or improved vibration isolation efficiency in soft soil conditions while promoting environmental sustainability using recyclable materials.

Enhancing the seismic performance of highway embankments on soft soils: a comparative study of conventional and T-shaped deep cement mixing columns

Enhancing the seismic performance of highway embankments on soft soils: a comparative study of conventional and T-shaped deep cement mixing columns

Numerical investigation of soil arching and integral abutment bridge in a pile-supported railway embankment

ABSTRACT Rail transport plays a crucial role in promoting sustainable mobility and tackling environmental challenges. However, the construction of a railway track on soft soil poses significant challenges due to the inherent instability and potential for excessive settlement. To address these issues, this study numerically assessed a pile-supported embankment and an integral abutment bridge. Two different numerical models are simulated in two-dimensional (2D) plane strain conditions. Findings from numerical analyses of the pile-supported embankment revealed that soil arching is significantly influenced by embankment height and pile spacing. The maximum settlement of the embankment decreases with an increase in embankment modulus and friction angle. Furthermore, a correlation among soil arching indicators was established. Conversely, the analysis of integral abutment railway bridges (IARBs) indicates that the performance of the transition zone is significantly influenced by factors such as approach slab geometry and multiple axle passages.

Global Sensitivity Analysis of the Fundamental Frequency of Jacket-Supported Offshore Wind Turbines Using Artificial Neural Networks

Determining the fundamental frequency of Offshore Wind Turbines (OWTs) is crucial to ensure the reliability and longevity of the structure. This study presents a global sensitivity analysis of the fundamental frequency of OWTs on jacket foundations. Monte Carlo sampling was employed to generate a diverse set of wind turbines, emplacements, and jacket designs, ensuring that the generated samples are realistic and yield relevant conclusions. The fundamental frequency and its partial derivatives were obtained via a previously developed ANN model. The relative sensitivities were computed to facilitate the comparison of their influence. The results demonstrate that wind turbine properties are the most relevant variables affecting the fundamental frequency, with a decrement in frequency caused by tower height and rotor-nacelle assembly mass, as well as an increment due to the section dimensions of the tower, particularly at its base. Soil properties have a significant effect on foundation stiffness for soft and light soils but can be neglected for hard and heavy soils. The diameter and thickness of the braces also show different relevance depending on their dimensions, producing rigid links between legs for greater sections. This study provides a measure of the variables influencing the fundamental frequency, facilitating a deeper comprehension of this phenomenon.

Three-Dimensional Numerical Analysis of Seismic Response of Steel Frame–Core Wall Structure with Basement Considering Soil–Structure Interaction Effects

In recent years, numerous studies highlighted the crucial role of the soil–structure interaction (SSI) in the seismic performance of basement structures. However, there remains a limited understanding of how this interaction affects buildings with basement structures under varying site conditions. Based on the three-dimensional (3D) numerical analysis method, the influence of the SSI on the seismic response of high-rise steel frame–core wall (SFCW) structures situated on shallow-box foundations were investigated in this study. To further investigate the effects of the SSI and site conditions, three types of soil profiles—soft, medium, and hard—were considered, along with a fixed-foundation model. The results were compared in terms of the maximum lateral displacement, inter-story drift ratio (IDR), acceleration amplification coefficient, and tensile damage for the SFCW structure under different site conditions, with both fixed-base and shallow-box foundation configurations. The findings highlight that the site conditions significantly affected the seismic performance of the SFCW structure, particularly in the soft soil, which increased the lateral deflection and inter-story drift. Moreover, compared with non-pulse-like ground motion, pulse-like ground motion resulted in a higher acceleration amplification coefficient and greater structural response in the SFCW structure. The RC core wall–basement slab junction was a critical region of stress concentration that exhibited a high sensitivity to the site conditions. Additionally, the maximum IDRs showed a more significant variation at incidence angles between 20 and 30 degrees, with a more pronounced effect at a seismic input intensity of 0.3 g than at 0.2 g.

A Cam Clay constitutive relation for semi-analytical elasto-plastic modeling of wheel-soil interaction for fast applications

In this paper, a semi-analytical elasto-plastic (SAEP) model is proposed to simulate wheel motion on soft soil using a Modified Cam Clay (MCC) constitutive model. The focus is on enhancing computational efficiency by integrating the MCC model into the framework. The MCC-based model outperforms the Drucker-Prager with Cap hardening (DPC)-based model in terms of reduced computation time, stability, and convergence. Simulations with a 30% slip ratio show a significant reduction in solution time compared to the DPC-based model. For slip ratios of 50% and 90%, the computation time decreases even further. Overall, the MCC-based model demonstrates over 100 times reduction in the solution time compared to the DPC-based model, particularly with high slip ratios. Indeed, the DPC-based model was found to be highly sensitive to high values of slip ratios, whereas the MCC-based model is not. In comparison with existing methods in the literature, the proposed formulation is superior in terms of significantly reduced solution time and improved numerical stability, making it ideal for advanced applications where fast solutions are crucial.

An experimental and numerical study on chloride transport in concrete under single bending load and coastal soft soil environment

This paper presents an experimental and numerical simulation study on the corrosion of chloride ions in concrete components, using a single pre-applied bending load to represent an additional bending moment caused by an external one-off disturbance. Besides, a novel correlation testing method, the Pearson-Mutual Information (PMI) method, is proposed based on Pearson correlation coefficients and mutual information theory. The findings indicate that a significant effect on chloride ion transport is only observed when the ratio of the applied bending load to the ultimate bending load (λ) exceeds 0.3. There is a distinctly positive and nonlinear relationship between λ and free chloride concentration (CCl), the apparent chloride diffusion coefficient (Da), as well as apparent surface chloride concentration (Cs). The bivariate time-varying model developed in this study demonstrates high fitting accuracy, with simulation results that closely correspond to actual measured data, achieving a coefficient of determination (R²) of 0.98 or higher. Furthermore, a sensitivity analysis of the model input parameters indicates that Cs is more sensitive than Da, and λ is identified as the key parameter. The impacts of the interfacial transition zone (ITZ) and its diffusion coefficient (Ditz) were found to be minimal on the output of the model.

Reinforcement of a Soft Soil Foundation Using Waste Soil Prefabricated Piles: A Case Study

Reinforcement of a Soft Soil Foundation Using Waste Soil Prefabricated Piles: A Case Study

Comparative Study of Semi-Active Control Effectiveness of Structures on Soft Soil Using MR Damper: Shaking Table Investigation

The effect of soil-structure interaction (SSI) cannot be neglected in semi-active vibration control of structures located on soft soil. To investigate the mitigating effect of magnetorheological (MR) damper on the semi-active control of structures considering the SSI, shaking table tests were conducted to evaluate the performance of the MR damper-based semi-active control system for structures on soft soil. In addition to a novel fuzzy control method based on online learning deep neural network (OL-DFNN), various control strategies, including passive OFF, passive ON, ON–OFF and deep neural network fuzzy control (DFNN) were systematically evaluated. The test results showed that the OL-DFNN control method exhibited superior adaptability to varying ground motion and structural dynamic characteristics compared to the other control methods. In particular, the OL-DFNN controller effectively mitigated the peak displacement and root mean square displacement, outperforming the passive OFF, passive ON, ON–OFF and DFNN control strategies. The test results highlight the effectiveness of the OL-DFNN control method in addressing the challenges posed by dynamic and time-varying characteristics in structural vibration control systems considering SSI.

Wall Deflection and Ground Surface Settlement due to Braced Deep Excavation in Soft-Soil Ground

An extensive database comprising more than 1,100 case histories of wall displacements and ground settlements due to deep excavations in soft soils created by Long, Moormann, and Wang et al. (2009) was analyzed. The applicability of the criteria for maximum lateral displacements and ground settlements using their database was analyzed. When excavation work is conducted under ground conditions where seaweed cohesive soil is distributed thickly, excessive horizontal displacement is expected to occur owing to low undrained shear strengths. Therefore, ground reinforcement was performed by applying a reinforcement method on the excavation side to secure a stability factor against a basal heave that exceeds 3.0. When using this method, applying the management standard for the maximum horizontal displacement, i.e., 0.3%H of the retaining wall, as the limit value is considered appropriate. This is expected to minimize the horizontal displacement of the retaining wall and the subsidence of the background during excavation work.

Experimental study on negative skin friction characteristics of double-sleeve pile

Pile foundation structures are widely used in the construction of high-piled wharves in coastal soft soil areas due to their excellent adaptability to such environments. However, the extensive, deep backfilling involved in constructing these wharves can easily induce negative skin friction (NSF) on the piles, resulting in safety issues such as excessive settlement during the service life of the structures. This paper presents an indoor model experiment to examine the distribution of the THE NSF under varying pile-top loads and surcharge effects on single pile and double-sleeve pile foundations. The potential of double-sleeve pile foundations to mitigate the NSF was also explored. The results show that the axial force within the double-sleeve pile’s protected section remains essentially stable, though it is affected by the surface surcharge in the unprotected section. Time effect is exhibited both for the axial force and the NSF, gradually increasing over time. Compared to single piles, double-casing pile foundations can effectively isolate the down drag load caused by surrounding soil settlement, thereby reducing or eliminating the NSF on the pile sides.

Analysis of Soil-Structure Interaction of Framed Structure

This study examines the soil-structure interaction (SSI) effects on the seismic behavior of G+7 and G+12 reinforced concrete buildings. Using finite element modelling in SAP2000, we assess key seismic parameters, including base shear, time period, lateral displacement, and footing settlement, across three soil types: soft, medium, and hard. This comparative analysis provides insights into how building height and soil flexibility influence structural stability, suggesting optimal design considerations for enhancing earthquake resilience. Key Words: Soil-Structure Interaction (SSI), Base Shear, Lateral Displacement, Seismic Analysis, G+7, G+12, SAP2000, Soft Soil, Medium Soil, Hard Soil.

Study on the strength characteristics and microscopic mechanism of sewage sludge ash modified lime soil

The large amount of sewage sludge ash (SSA) generated by incineration treatment of sewage sludge each year can seriously pollute the environment, and there is an urgent need to seek an effective resource utilization method for SSA treatment. SSA has the significant pozzolanic activity, and can be used as an auxiliary cementitious material. For that, SSA was adopted to modify lime soil in this work. The strength characteristics of SSA modified lime soil (SLS) were investigated by conducting unconfined compressive strength test and unconsolidated-undrained triaxial compression test, and X-ray diffraction (XRD) test and scanning electron microscopy (SEM) test were conducted to investigate the mineral composition, microstructure and porosity of SLS. It is observed that the unconfined compressive strength (UCS) increases first and then decreases with increasing SSA content in the range of 0–20 %, and reaches the maximum value while SSA content is 15 %, which increases by 25 % at the curing age of 28 days comparing to the specimen without SSA. Additionally, the triaxial strength and cohesive force both have the same change law as UCS with SSA increasing, and 15 % can be used as the optimal content of SSA to modify lime soil. The added SSA can promote the pozzolanic reaction, and more hydration products fill the specimen porosity so that the specimen strength can be improved. Furthermore, the porosity of SLS decreases first and then increases with SSA content increasing, and there is a linear relationship between the porosity and strength of SLS. Finally, a simple function is proposed, which can simulate the quantitative relationship between UCS and the triaxial strength with satisfying accuracy. Generally, the research results can be used as a reference for the application of SSA in soft soil foundation treatment.

Clayey soil stabilisation with geopolymerized olivine and glass fibers

In some engineering applications soil stiffness only could not be a reliable parameter in accordance with specific standardizations especially when dealing with dynamic loading. In other words, foundation soil should be altered regarding its ductility in order to prevent sudden damage due to brittleness. Plenty of researchers were concerned to focus on soil reinforcement using glass fibers. Besides, the alkaline activation method has been adapted to alter the strength properties of soft soil. Furthermore, recent alkaline activation of soft soil, using olivine and Potassium hydroxide, coupled with soil reinforcement was adapted to change the post-peak behavior of soft soil. The aim was towards ultimate strength increase and enhancement of failure mode. In this research, geopolymerized soil and geopolymerized reinforced soil were cured for 7, 28, 90 and 180 days respectively. Compressive stress tests were conducted on both mixtures namely SO and SOG samples. Results drawn from the tests revealed a drastic increase in compressive strength for SO samples cured for 28 and 90 days, namely 3,64 MPa and 7,5 MPa respectively. Though a sharp drop was seen when approaching failure. With the addition of reinforcing glass fibers for the suggested curing regimes the failure mode was enhanced to become more ductile.

Experimental Investigation of the Axial Load Capacity of Bilateral Helix-Stiffened Cement Mixing Piles in Soft Marine Soil

Bilateral helix-stiffened cement mixing piles (BHCMPs) are a new type of robust composite pile. In this paper, the influence of design parameters, such as the diameter of inner helix plates and the number and size of outer mixing helix plates, on the vertical bearing performance of the pile foundation and the behavior of the pile diameter are investigated through laboratory model tests. The results indicate that incorporating a reverse-mixing process in the pile formation of helix-stiffened cement mixing piles can enhance the overall ultimate bearing capacity and strengthen the soil-cement of the piles. In the case of the same double-blade inner drill pipe, for every 22 mm increase in the blades, its ultimate compressive load-bearing capacity was increased by 10% to 25%, and its pullout load-bearing capacity was increased by 15% to 45%. With further increases in the blades, the percentage increase in the compressive and pullout load-bearing capacity was reduced. With an increase in the number of external mixing blades, its compressive load capacity increased in the range of 5% to 20%, and the elevation load capacity increased in the range of 10% to 25%. Increasing the number of reverse-mixing helix plates on the outer casing enhances the soil-cement strength of the pile body by approximately 15–20% for each additional plate. The average strength of the pile-body soil-cement for each additional plate is estimated to be 1 to 1.4 times that of the previous set, indicating that increased mixing iterations can enhance the perimeter soil-cement strength of the pile. The average bond diameter of soil-cement piles with double-blade internal drilling rods could be seen from the diameter of the piles formed, which was 1.02 to 1.21 times the diameter of the blades.

Load transfer mechanism of floating pile-supported embankments under cyclic loading

Pile-supported embankments are one of the most commonly used techniques for ground improvement in soft soil areas. Existing studies have mainly focused on embankments supported by end-bearing piles under static loading, with limited research on floating pile-supported embankments under cyclic traffic loading. In this study, model tests for unreinforced floating, unreinforced end-bearing, geosynthetic reinforced floating, and geosynthetic reinforced end-bearing pile-supported embankments were conducted. Cyclic traffic loading was simulated using a three-stage semi-sinusoidal cyclic loading. Comparative analyses and discussions are performed under floating and end-bearing conditions to investigate the influence of floating piles on the soil arching evolution and membrane effect under cyclic loading. The results indicate that floating piles result in earlier stabilization of surface settlement. There is less arching and membrane effect induced by floating piles, and the arching does not continue to degrade under cyclic loading. Less membrane effect in floating pile-supported embankments results in less geosynthetic and pile strain. The degree of membrane effect in floating pile-supported embankment largely depends on the pile-end condition.

3-Dimensional numerical analysis of geosynthetic double-encased annulus stone columns

A geosynthetic double-encapsulated annulus stone column technique is proposed in this study to overcome limitations associated with conventional stone columns, such as limited lateral load-bearing capacity and potential issues related to aggregate dispersion in soft soils. Geosynthetic double-encapsulated annulus stone columns are consistent with conventional stone columns besides being confined in and around the surrounding soil. The performance of geosynthetic double-encapsulated annulus stone columns is primarily dependent upon their outer-to-inner diameter ratio. For this reason, comprehensive 3-dimensional numerical studies were carried out to evaluate the optimum outer-to-inner diameter ratio of the annulus stone column. The results suggest that the ultimate load-carrying capacity of an annulus stone column increases with an increasing ratio of outer to inner diameter until an optimum value. In addition, the double encapsulation enhances confinement, improving shear stiffness and reducing lateral bulging. However, the load-carrying capacity was substantially reduced beyond the critical outer-to-inner diameter ratio. A simple analytical model extending the theory of thin cylinders is also introduced to estimate the accumulated stresses and strains in the geosynthetic encasement. The proposed model operates within a simplified framework of elastic solutions that facilitate practising engineers to design and optimize geosynthetic encasements for enhanced structural performance.

Estimation of Vs30 and site classification of Bhaktapur district, Nepal using microtremor array measurement

The severe damage observed in the Kathmandu Basin, Nepal, during past earthquakes necessitates a thorough study of the seismic behavior of the basin sediments. As the shear-wave velocity is directly related to the elastic shear modulus of the material, it is essential to determine it to incorporate the behavior of the soil in the design of the structure. Hence, we determined average shear-wave velocity in upper 30 m (Vs30) of soil in Bhaktapur district in the eastern part of the Kathmandu Basin at 73 observation points, employing two methods involving the use of non-invasive microtremor array measurements (MAMs). These MAMs are widely used for determining subsurface soil characteristics by analyzing the ambient vibrations of the ground. The first method involves inversion using a genetic algorithm, and the second is a method for obtaining Vs30 directly from the dispersion curve. We found that Vs30 in the southeastern part of the study area was higher than that in other parts. Conversely, Vs30 in the western region was lower. The calculated Vs30 values were used to classify the sites. The elevated eastern and southeastern areas with high Vs30 were categorized as dense soil or soft rock, whereas the areas with low Vs30 that had suffered significant damage during the 2015 Gorkha earthquake were classified as soft soil sites.Graphical