Soil Compression Research Articles

LESSONS LEARNT FROM SOIL IMPROVEMENT CASE STUDIES

In Saudi Arabia two methods of soil improvement have been customarily employed. They are soil improvement by means of stone columns, and soil improvement by means of controlled modulus columns, that is CMC. Each of these methods have their own challenges to offer. Experience has shown that the sub-surface geology of the coastal areas of Saudi Arabia are marked with deep layers of poor soil termed locally as sabkha soil. Test results have determined that sabkha soil is known to have low shear strength, high soil compressibility, and high concentration of chlorides and sulphates which are corrosive to concrete, steel, and other construction materials. Design of foundations over a sabkha deposit remains a challenge and requires soil improvement. The CMC installation utilizes reverse flight augers, which displaces the soil laterally. However, it offers a huge challenge of post-operation trimming and cutting of CMCs. for stone columns, soil is removed during the drilling operation creating environmental issue. It also offers challenges as the huge impact during its operation are likely to damage the underground utilities. The environmental issues thus created can pose yet other challenge. This research paper is a case study that collates the experiences of soil improvement methods employed on a project in Saudi Arabia – vis-à-vis their advantages and the challenges encountered.

Shear Strength and Durability of Expansive Soil Treated with Recycled Gypsum and Rice Husk Ash

Expansive soil underlying structures pose a significant risk to the integrity of superstructures. Chemical soil stabilization can be used to strengthen soils due to the cost and impracticality of mechanical approaches. Waste materials such as recycled gypsum and rice husk ash have been considered alternatives because of their sustainable and economic advantages. A combination of these additives was used to address the high absorption of gypsum and the lack of cohesion of the pozzolan. The study assessed the short-term and long-term performance of expansive soil treated with recycled gypsum and rice husk ash under normal and fluctuating moisture conditions. Direct shear tests indicated ductile and compressive soil behavior with improved shear strength. A good approximation of stress–strain response was made with a modified hyperbolic model for treated soils that exhibited strain hardening and compressive volumetric strain. Durability and water immersion tests were performed for samples after varying curing periods and cycles of capillary soaking to assess the behavior when exposed to varied environmental conditions. Samples under the modified durability test experienced significant strength loss, with decreasing compressive strength as curing durations increased. Specimens in the modified water immersion test experienced significant strength loss; however, it was determined that curing durations did not contribute to the change in the strength of the sample. Expansion index tests also determined that the treatment effectively mitigated expansivity and collapsibility in all samples. Despite improvement in shear strength and expansion potential, further investigation is needed to enhance the durability of soil treated with gypsum and rice husk ash.

Effect of stabilizing subgrade layer using various additives on the flexible pavement design

Soil stabilization involves enhancing the physical properties of soil to increase its stability, durability, and ability to support heavy loads, making it a crucial technique in civil engineering and construction. The process is used to reduce soil permeability and compressibility and increase its shear strength. To achieve this, various additives are used. This paper evaluates RoadCem (nanomaterial) and traditional additives such as cement, lime, and ashes materials such as rice husk ash (RHA) and fly ash (FA) as by-product materials in clayey soil stabilization. The used percentages of Lime were (2, 4, 6, and 8%), cement and RoadCem (3, 6, 9, and 12%), FA (3, 6, 9, 12, and 15%), and RHA (5, 10, 15, 20, and 25%) by dry weight of the tested soil. Various tests were used to examine and evaluate the physical and engineering characteristics of the treated soil, modified proctor, atterberg limits, free swelling (FS%), unconfined compressive strength (UCS), California bearing ratio (CBR), and resilient modulus (Mr) as well as microstructure tests [scanning electron microscopic (SEM)]. All admixtures were tested and subjected to two curing periods, 7 and 28 days. The results indicated that the optimum additives percentages were selected as 6% FA and 15% RHA activated by 6% lime and 6% for both RoadCem and cement. At these percentages, plasticity, FS%, and optimum moisture content (OMC) values were decreased. In contrast, maximum dry density (MDD), UCS, CBR%, and Mr values were increased. In addition, the correlation between Mr and both CBR and UCS was drawn. SEM results showed that major changes were observed in the microstructure of treated samples due to the forming of cementitious materials. The study evaluated the effect of subgrade stabilization on reducing base layer thickness under light, medium, and heavy expected traffic loads with an economic analysis to examine the benefits of subgrade stabilization. The cost analysis showed that the optimal economic additives were RoadCem and cement.

Experimental Studies on Ground Improvement Using Stone Column

This research examined the ground improvement technique for enhancing the load-bearing capacity and enhancing of weak or compressible soils. In this study, we focus on how we minimize the cost of ground improvement and make environment friendly solution for ground improvement. The research involves a review of the existing literature, including the Objectives, methodology, and case studies related to stone column implementation. Laboratory testing and field investigations are conducted to assess the geotechnical properties of the soil and the behavior of stone columns under different loading conditions. The project aims to provide insights into the geotechnical behavior of stone columns and their effectiveness in stabilizing weak soils. Furthermore, the study will explore the economic and environmental aspects of this ground improvement technique. The findings of this research are expected to contribute valuable knowledge to the field of geotechnical engineering, assisting engineers and construction professionals in making informed decisions regarding ground improvement methods. Keywords : Ground Improvement, Stone Column, Soil Sample, cost effective, environment friendly, Load Bearing Capacity, Black Cotton Soil, Soil Stabilization.

New simple method for calculating large-strain consolidation settlement of layered soft soils with horizontal drains and vacuum preloading with comparison to test data

Prefabricated horizontal drains and vacuum preloading have advantages in the consolidation of ultra-soft dredged sludge and soils for maintenance dredging, reclamation, and ground improvement in coastal regions. While laboratory tests and field trial projects have been reported, a convenient analysis and design method is still unavailable. This study proposes a new simple method for the settlement analysis of soft soils considering horizontal drains, vacuum preloading, creep, and large-strain effects. A unified equation is constructed to account for various layouts of horizontal drains in consolidation. A new explicit method is developed to consider the large-strain deformation with the nonlinear evolution of permeability and compressibility of ultra-soft soils under vacuum preloading. The viscous compression is taken into account using a simplified Hypothesis B method. The proposed solution also facilitates convenient consideration of multiple layers of soils and drains subjected to staged loading. The proposed method is examined by a series of physical model tests with different horizontal drain dimensions. Finally, the method is applied in the analysis of two well-documented field cases in Hong Kong and Japan, which confirms its effectiveness and accuracy.

The Effect of Oil Pollution on the Engineering Properties of Construction Soils in Some Selected Oil Region of Nigeria: A Case Study of Four Oil Towns in Rivers and Delta States

The nature of subgrade as well as basic information of soils for construction purposes is important for engineers, especially civil engineers and the general public. The primary aim of this research work is therefore to access the effect of oil spillage on the engineering properties of soils around the oil producing states of Nigeria. Four communities in two state of the Niger- Delta region of Nigeria were selected for investigation. These communities include Alesa (as sample A) and Aleto (as sample B) in Rivers state and Elume (as sample C) and Mereje (as sample D) in Delta state of the Niger- Delta region of Nigeria. Soil samples from these communities were collected at the subgrade depth of the oil spilled soils and was later subjected to laboratory examination. Important soil properties that were evaluated through laboratory investigation include soil shear strength test using triaxial test where the shear strength parameters were determined to enable evaluation of soil bearing capacity using Terzaghi’s equations. Others include soil strength (CBR) test, soil permeability test, and soil classification test as well as soil compressibility tests or one dimensional consolidation test. The results show that the oil pollution/ spillage have affected the engineering properties of construction soils in the four towns investigated to some degrees. The California Bearing Ratio (CBR) value of the subgrade, the Coefficient of Volume Compressibility,Mv, the Safe Bearing Capacity and the Coefficient of Permeability, K of the investigated soil , all fall below the accepted standard limit for soils to be used for construction purposes. This result will hopefully add to the existing knowledge as well as equipping the government and other relevant agencies for policy and regulatory development for the oil and gas, and construction industries for the sustenance of economic development in Nigeria. Therefore, before any meaningful civil engineering construction works can be done in these communities, the soils within the area will have to be subjected to series of engineering soil tests so as to equip the government and other interesting stakeholders with the requisite knowledge on how to apply appropriate soil remediation and soil stabilization techniques.

Comparing Geotechnical Methods to Assess Primary Consolidation Settlements for Raft Foundations

The primary consolidation settlements in soils under pressure due to raft foundations were evaluated using the Excel DISBAL book, and the results of the classical procedure for calculating primary settlements, taking into account the soil compression index, were compared with those of the simplified procedure based on the summation of layers method, recommended by the current Cuban standard of surface foundations. The novelty of Excel DISBAL book is its contribution for solving shortcomings of software based on current geotechnical methods and in accordance with the legal framework of current construction regulations in Cuba and other international references. The case study deals with the evaluation of the extension in height of a building supported in soil deformation limit state and hypothetically located in the experimental field of Civil Engineering of Universidad de Oriente, where the coves were made by the National Research Company Applied from Santiago de Cuba. It is demonstrated that this software allows an adequate assessment of the limit state due to soil deformation by both methods, obtaining acceptable primary consolidation settlements for the case study, and helping to specify the number of floors the building will reach.

Simulating earth deformation evolution caused by groundwater pumping through ordinary state-based Peridynamics method

Earth deformation including land subsidence and the related earth fissures caused by the over-exploitation of groundwater resources is threatening countries all over the World. At present, the simulation of earth deformation of aquifer system is mainly based on continuum and contact mechanics. These approaches lead to two main challenges, i.e. the need of knowing the location of possible earth fissures in advance and using meshes that must be adjusted during the rupture propagation. Here, ordinary state-based Peridynamics method is firstly introduced to simulate the evolution of continuous and discontinuous earth deformation due to groundwater withdrawal. A failure criteria accounting for shear and tensile strain simultaneously is proposed. The approach is used to simulate the evolution of land subsidence and earth fissures in compressible sedimentary soils with buried rigid ridges. Two case studies are reproduced: one is a test carried out in laboratory and the other one concerns Guangming village, Yangtze River delta. In both cases, the presence of a shallow buried bedrock crossing the alluvial deposits is responsible for the initiation and growth of earth fissure that a satisfactory captured by the model. For the lab experiment, a 0.1 m deep fissure appearing above the rocky tip is computed. In Guangming village area, results show that some small fissure groups were initiated. Then, three main earth fissures developed rapidly with the maximum depth of 32.5 m. This study proposes a consistency modelling framework to simulate continuum earth deformation and discontinuous fissures due to groundwater withdrawal in specific geological settings, and supply a reliable scientific tool for early warning of this geo-hazard.

Limiting physical properties of Technosols formed by the Fundão dam failure, Minas Gerais, Brazil

ABSTRACT Physical properties of the Technosols formed by the tailings deposition may constitute a physical barrier that limits water movement and plant development due to the properties received from those sediments. This study aimed to evaluate the physical quality of the Technosols formed by the deposition of sediments displaced by the Fundão Dam failure, Mariana, Minas Gerais State, Brazil, based on the evaluation of physical properties and Load Bearing Capacity Models (LBCM). For that, three areas under different vegetation types were selected: eucalyptus (Euc), forest with human-assisted revegetation (RF), and forest with native vegetation (NF). Three sampling subareas were demarcated in each area: non-impacted areas (Ni), and Technosols formed in directly impacted areas (Di), and partially impacted areas (Pi). Undisturbed samples were collected in two layers and subjected to the uniaxial compression test after equilibration at five matric potentials. Soil compression curves and LBCM were determined. Soil bulk density (BD), total porosity (TP), organic matter (OM), granulometry, and particle density (PD) were also determined. Clay content was less significant, and the silt and very fine sand content was significantly higher in the Technosols, generating an increase in BD and reduction in TP. Technosols generally exhibited greater load-bearing capacity due to higher pre-consolidation pressure values attained by these soils due to the lower clay and OM contents. High resistance of these soils is one limitation for revegetation of the areas evaluated, being necessary management practices to improve physical properties of the Technosols.

Intrinsic compressibility of laterites and lateritic soils

Laterites and lateritic soils, prevalent in tropical and subtropical climates, have growing applications in earthwork construction. They usually present unique compression properties compared to conventional clays. Therefore, a thorough understanding of their intrinsic compressibility is crucial. This paper reports on modified oedometer tests conducted on reconstituted samples of four distinct laterites and lateritic soils with varying initial water contents. In addition, scanning electron microscopy (SEM) was utilized to identify the microstructural features to reveal the mechanisms of intrinsic compression. The results demonstrate that intrinsic compression curves of reconstituted laterites and lateritic soils align with Burland’s normalization framework. However, they exhibit a higher void ratio at an effective vertical stress of 100 kPa ( e* 100) and a lower compression index ( C* c) compared to traditional clays; therefore, existing formulas for calculating e* 100 and C* c are inapplicable to laterites and lateritic soils. The SEM analysis revealed that sesquioxide interacts with soil minerals, resulting in a porous structure and robust inter-unit cementation. This unique microstructure contributes to the observed intrinsic constants of compressibility, e* 100 and C* c. Based on the experimental observations, new empirical equations are introduced to evaluate e* 100 and C* c in laterites and lateritic soils. The experimental results elucidate the role of sesquioxide in inherent compressibility and improve our understanding of compressibility characteristics that are unique to laterites and lateritic soils.

The influence of soil specimens shape and dimensions on consolidation parameters used in foundation settlement prediction

The theory of elasticity is used in geotechnical engineering for the calculation of foundation settlement. The equation used in the evaluation of consolidation settlement uses the soil compressibility parameters which usually are determined on cylindrical soil specimens with ϕ 71.4 mm. Laboratory tests performed on soil specimens showed that the parameters that are used in foundation settlement analysis are influenced by the dimensions of the tested soil specimens and the shape of that specimen. The paper presents the influence of specimen size, shape and method used for the coefficient of consolidation evaluation on the final value of the foundation settlement. The analysis was performed using the Settle3 software from Rocsience, considering the case of an elastic foundation flexible square foundation (1.5 m × 1.5 m) which transmits to the ground a pressure of 100 kPa.

Experimental study of ground improvement techniques of soft Kaolin soil using sand drain and jute wrapped with polyamide polyester vertical drain”

Thick alluvial deposits of soft clayey soils are characterized by low shear strength, high compressibility and low hydraulic conductivity. In recent years, soil improvement is required to provide adequate bearing capacity and improve shear strength of the soft cohesive soils to satisfy the need for various type of construction on sites underlain by such soft soils. Amongst various ground improvement techniques like vibroflotation, compaction with explosive, electro-osmosis, heavy tamping, stone column etc., the technique of preloading or pre-compression used in combination with vertical drains is one of the oldest and most widely used techniques to preconsolidate and strengthen weak compressible soils in situ. To accelerate the time of Primary consolidation, Prefabricated Vertical drains are used in soft clays as they decrease the drainage path. In this paper, we investigate the consolidation rate of soft soil with Sand drain and jute wrapped with polyamide polyester drain as PVD. The present paper focuses on Study of pore water dissipation, effect on consolidation due to radial drainage flow and gain in strength using 254 mm diameter Rowe Type Oedometer for both the drain materials. The load in increment of ΔP/P = 1 is applied and measurement of settlement by conventional method is done. It is observed that Jute wrapped with polyamide polyester drain as PVD performs better in comparison to Sand Drain.

Impacts of aquifer heterogeneity on subsidence resulting from engineering dewatering in the Lower Yangtze River plains

Study regionLower Yangtze River alluvial plain, China. Study focusThe uneven subsidence caused by dewatering in underground engineering constructions in densely populated areas of alluvial plains with an unevenly distributed medium has caused increased concerns. This study applied the transition probability geostatistical software (T-PROGS) geostatistical models based on data from 31 boreholes to characterize a three-dimensional (3D) heterogeneous aquifer (8.8×105 m2 in area and 56 m in depth) in an underground construction area in the alluvial plain of the lower Yangtze River. The SUB model was constructed to simulate the pumping-induced subsidence processes based on a reliable MODFLOW transit flow model. New hydrological insightsThe simulation results indicated that surface subsidence increased with pumping and reached a maximum of 33 mm by the end of the extraction (the 14th day). Surface subsidence development exhibited spatial anisotropy around the pumping center, consistent with the observations. Furthermore, the proposed model indicates that hydraulic head evolution and soil compressibility distributions significantly influence the spatial–temporal development of subsidence, implying the significance of the aquifer heterogeneity. The compressible soft soil overlying the pumping section was identified as a vulnerable subsidence zone, suggesting its significance for engineering geological surveys and dewatering designs in underground construction in alluvial plains.

Insights into water absorption characteristics of various waste-based inorganic additives and their application for soil stabilization

Cement is the most important binding agent used in soil stabilization and significantly improves the strength and compressibility of soils. However, owing to the significant environmental and socio-economic impact of cement production, alternative, low-carbon binders are increasingly being sought. Among them, waste-based inorganic additives used in construction provide sustainable soil treatment materials and reduce the need for landfills. Effective mud stabilization depends on the type of stabilizers and their mineralogical setup, as well as an understanding of their water absorption capacity. Therefore, this study investigated the factors influencing the water absorption characteristics of waste-based additives, including paper sludge ash (PSA), palm kernel shell ash (PKSA), rice husk ash (RHA), coal fly ash, hemihydrate gypsum, limestone powder, and basalt rock powder (BRP). The water absorption capacity (Wab) of each additive represents the amount of water absorbed per gram evaluated via the suction filtration method. The long-term water absorption capacities of the waste additives were compared with a conventional additive, blast furnace cement class B (BFCB). Although PSA, PKSA, and RHA absorbed more water than BFCB under short-term curing, BFCB exhibited the highest Wab under long-term curing. PSA, PKSA, and RHA had a water absorption capacity at 4 h (Wab)t = 4h of 74.5%, 107.3%, and 62.9%, respectively, whereas that of BFCB was 37.4%. In contrast, after 168 h, the water absorption capacity of BFCB increased to 126.1%. These evaluated water absorption capacities were categorized into immediate and time-dependent stages. Mercury intrusion porosimetry, X-ray diffraction (XRD), and scanning electron microscopy investigations were conducted to investigate the influence of factors such as porosity and hydration of the different additives on water absorption capacity. The results showed that porosity characteristics affect the immediate water absorption capacity, and hydrate formation contributes to increased water absorption during curing. The waste additives PSA, PKSA, and RHA with irregular surfaces and pores were highly porous and exhibited a high immediate water absorption capacity (Wab)t = 4h, unlike the additives with flat surfaces and less irregularities with lower (Wab)t = 4h. The XRD investigation revealed that the presence of ettringite and calcite contributed to increased water absorption during curing for PSA, PKSA, and BFCB. The generation of needle-like ettringite could promote a denser microstructure in PSA, PKSA, and BFCB, thus further improving Wab during curing. Finally, using cone index strength, we explored the effective application of waste-based additives as soil stabilizers, attempting to predict the effect of water absorption capacity on the properties of treated soil. The stabilizer addition ratio (A) and Wab of the waste additives were found to be essential indicators for predicting the strength development of treated clays. A clear correlation was observed between the cone index (qc) and parameter β(t), which is derived from Wab and A, of the treated clays.

Semi‐analytical solution for double‐layered elliptical cylindrical foundation model improved by prefabricated vertical drains

AbstractThis work proposes a semi‐analytical solution for a double‐layered elliptical cylindrical soft foundation improved by prefabricated vertical drains. The governing equations, continuity conditions are boundary conditions in the elliptical cylindrical system are introduced first. The Laplace transform is employed to convert the time variable t in partial differential equations into the Laplace complex argument s. Based on the boundary condition and continuity condition, the solution in the frequency domain is derived. By using Abate's fixed Euler Algorithm, the solutions in the time domain are obtained. A finite element analysis is performed to demonstrate the accuracy of the proposed solution. Then, parametric studies reveal that soil permeability and soil compressibility have great influences on the second layer of soil in the elliptical cylindrical system, but relatively small effects on the first layer. Neglecting differences in the hydraulic conductivity and the coefficient of volume compressibility of multi‐layered soil in the elliptical cylindrical system could not predict the excess pore pressure in the second layer correctly.

Compaction, compression, and hydraulic characteristics of micaceous residual soil

Compaction, compression, and hydraulic characteristics of micaceous residual soil

Numerical Investigation of Two Methods to Reduce the Settlement of a Light-Weight Highway Embankment on Soft Soils

The development of road and highway networks sometimes involves passing through compressible soils of poor quality. Given their mechanical properties as foundation soils, these soils are characterized by low short-term shear strength, expressed by undrained cohesion, which increases during soil consolidation, and are also characterized by significant compressibility, resulting in large-scale settlements when a load is applied to them. Nowadays, there are reinforcement methods that make it possible to execute these structures while limiting the risks of instability. This study consists of the numerical analysis of a light-weight embankment of a highway section built on soft soils. Two reinforcement methods are investigated to support the embankment layers and reduce settlement. Interest is given to the behavior of the soils in place before and after the installation of the adopted reinforcement. The analysis is carried out in such a way as to show the importance of the complete consolidation of the soils in place in the long term, which makes it possible to take into account the dissipation of the pore pressures.

Air-boosted vacuum preloading method for land reclamation with vertical drains: Numerical and analytical solutions

As an emerging ground treatment technique, the air-boosted vacuum preloading method accelerates the consolidation process of soils with vertical drains and enhances the bearing capacity and stability of grounds. This improvement is achieved by augmenting the horizontal pressure differential between the drainage body and the surrounding soils. In the realm of existing theories, consolidation models are primarily established under the assumption of linear characteristics of soils. Nonetheless, for marine sedimentary soft soils characterized by high compressibility, the application of nonlinear consolidation theory becomes more appropriate. The well resistance effect of the drainage body over time is also considered in this study, and a comprehensive consolidation model tailored to soft soils with air-booster pipes and vertical drains is proposed. Subsequently, the analytical and numerical solutions for this consolidation model are derived, respectively. Comparisons are made with existing conventional linear consolidation models to substantiate the validity of the proposed consolidation model. This investigation delves into the influence of nonlinear compressibility and permeability of soils, variable well resistance, and drain spacing ratio, on consolidation behaviors. Particular emphasis is placed on the determination of the startup time for the air-boosted system. Finally, the proposed consolidation model is applied to the actual field prediction, affirming the accuracy and applicability of the developed consolidation model in practical soft soil treatments.

ESTIMATION DES TASSEMENTS DIFFÉRENTIELS DES SOLS DE FONDATION DE BÂTIMENT : CONTRIBUTION DES SONDAGES DE RÉSISTIVITÉ ÉLECTRIQUE

To estimate differential settlements of building foundation soils, the site on which the structure is based must be geotechnically surveyed in order to determine the deformation parameters and the thickness of the compressible soil layers in various places. This involves conducting destructive surveys. In this study, the use of geophysical methods (electrical soundings) as a substitute for the conventional methods used was considered. The Schlumberger electrodes array was deployed at the level of a control borehole and at three projected footings. The combination of the results of the electrical soundings with the lithological section of the borehole reveals a significant correlation between the variations of cumulative resistivities and the lithological section of the subsoil. The thickness of the compressible layers at the level of the projected footings is estimated to vary between 5 and 6 m. Œdometric differential settlements have an estimated maximum value of 4.56 cm

Modelling the evolution of water retention hysteresis loops during soil deformation based on the ink‐bottle effect

AbstractThe ink‐bottle effect, resulting from the heterogeneous pore structure, plays a significant role in the hydraulic hysteresis of water retention behavior. Experimental evidence indicates that volumetric deformation extensively influences the hysteresis characteristics of the soil‐water retention curve (SWRC). This paper presents a physical–based model that aims to simulate the contraction of the hysteresis loop in the SWRC during soil compression by considering the evolution of the ink‐bottle effect. Within the proposed model, it is assumed that the suction increment is consumed in two distinct manners: to overcome the ink‐bottle effect and to alter soil saturation. As soil undergoes compression, the ink‐bottle effect weakens, resulting in a reduced proportion of suction consumed in counteracting this effect. To quantitatively describe the impact of ink‐bottle effect evolution on SWRC hysteresis, a novel concept known as hysteresis potential is introduced, which is defined as the difference in natural logarithmic values of suction between the drying and wetting curves at a given saturation. Finally, the proposed model was validated using five sets of experimental data, affirming its capability to capture the hysteresis loop evolution in SWRC attributed to the weakening of the ink‐bottle effect during soil compression.