Clayey Silty Sand Research Articles

A generalized water retention model in a wide suction range considering the initial void ratio and its verification

A generalized water retention curve (WRC) model in a wide suction range considering the initial void ratio is presented in this paper. Both capillary and adsorbed water in soil pores are considered. Based on the experimental results that the adsorbed water content wa is not dependent on the initial void ratio, a new degree of saturation equation of adsorbed water is established. Meanwhile, a new degree of saturation equation of capillary water at various initial void ratios is proposed with a void ratio-related expression of the air entry value. Compared to Lu’s model, only one parameter b is introduced in the established model, which can be easily calibrated using WRCs under two initial void ratios. The measured WRC results of 5 soils are used to verify the proposed model in comparison with the other 3 widely used WRC models. The soil used in the model validation covers a wide range of soil types from sandy soil to clay soil, including clayey silty sand, sandy clay till, clayey silt, expansive soil and lateritic soil. The proposed model is well verified for its ability to describe soil water retention characteristics in a wide suction range at various initial void ratios.

Assessment and Characterization of Woji Creek Riverbed in Port Harcourt, Rivers State, Nigeria, Utilizing Side Scan Sonar Technology

Woji Creek plays a crucial role in vessel navigation, supports diverse flora and fauna habitats, and sustains local livelihoods. However, human activities and natural events have led to changes in its riverbed over time. Given its significance for coastal stability and geomorphology, there is a pressing need to classify, evaluate, and ensure its environmental sustainability. The primary objective of this study is to employ side scan sonar technology to classify and assess the riverbed of Woji Creek in Port Harcourt, Nigeria. The study aims to classify the riverbed, analyze water depth variations, evaluate navigational suitability, and determine turbidity levels within the creek. To achieve these objectives, the methodology involved acquiring Side-Scan Sonar (SSS) and Sub-bottom profile data. These datasets underwent backscatter processing to create geocoded backscatter images. Feature points were extracted and matched from these images to derive riverbed classification, depth categories, water volume distribution, and river turbidity analysis. The riverbed classification revealed the presence of three primary sediment types: Clayey Silty Sand, Silty Clay, and Silty Sand, each with distinct implications for navigation. Shallow, Moderate, Deep, and Very Deep areas were identified within Woji Creek, each influencing navigational conditions. Additionally, the water volume distribution analysis provided essential insights into depth limitations and route planning.
 Moreover, the assessment of river turbidity identified low, moderate, and high turbidity zones, reflecting water clarity and suspended particle levels. These findings serve as invaluable decision support tools for navigation planning and management in Woji Creek, offering comprehensive insights into the riverbed, depth suitability, volume distribution, and water quality. Leveraging this data can enhance strategic decision-making processes and contribute to the sustainable management of this vital waterway.

The effect of EPB face pressure on TBM performance parameters in different geological formations of Istanbul

This study summarizes the effect of EPB pressure varying from 0.5 bar to 4 bar, on TBM performance i.e., on thrust force, torque, penetration, and specific energy. 6511 data points were analyzed, each representing mean values attributed to different segments of 1.5 m in length, in four different fractured hard rock formations, in a transition/weathered complex zone, and in silty-clayey sand. From this study, it emerges that thrust and torque values almost increase up to 2.2 and 1.7 times with EPB face pressure changing from 0.5 to 4 bar in all formations studied except for torque in silty-clayey sand. However, after 2 bar of face pressure, the effect of EPB pressure on penetration and specific energy is more remarkable than the other parameters. Specific energy increases almost 2–2.5 times in silty-clayey sand and up to 4 times in a transition/weathered zone. To contribute to understanding better the factors affecting TBM performance in fractured hard rock, the effects of geological and geotechnical parameters are also discussed briefly. We think the results will serve as a basis to understand better the effect of EPB face pressures on TBM performance, to design more efficient EPB-TBMs, and to help to develop new performance prediction models for EPB-TBMs working in fractured hard rock formations and in soft ground if some correction coefficients as will be developed later, are added to previously published models. However, it is strongly recommended to use the results of this article for tunnels having similar geological conditions as in Istanbul.

Landslide Soil Failure Parameters Characterization Using Geoelectrical Resistivity Methods in Uruagu, Nnewi, Anambra State, Nigeria

Electrical Resistivity Imaging (ERI) and Vertical Electrical Sounding (VES) were deployed over the Uruagu landslide area. The main purpose of the study was to characterize the landslide failure parameters in to identify the soil failure mechanisms. Ten profiles of 2D ERI measuring 200 m each, and thirty VES, with three VES along each profile, were executed. Nine of the ten profiles were executed within the landslide site while one profile was executed in a residential street as a control profile. Four soil samples were also taken for physical and geotechnical laboratory index analysis. The PASI resistivity meter was used for the geoelectrical resistivity measurements. The Wenner-Schlumberger array was deployed for the ERI with a minimum electrode spacing of 10 m. The Schlumberger array was deployed for the VES with a maximum current spacing of 130 m. ERI resistivity data analysis involved inversion using the RES2DINV software package involving mean model residual and construction of iso-apparent resistivity contour maps. VES resistivity data analysis involved calculated parameters from plotted field data on a log-log graph then used as initial models in an iterative forward modeling WinResist software package. The results of the ERI and VES for the control profile reveal that the subsurface strata are originally composed of silty clay of resistivity values (16.7 – 60.9) Ωm, clayey silty sand having resistivity values (116 – 800) Ωm and sandstone layer with resistivity values (>814 Ωm). The ERI and VES results for the devastated landslide site reveal counteraction material of resistivity values (>814 Ωm), colluvia and regoliths (116 - 300 Ωm), and variably wet weathered sandstones of resistivity values (<60.9 Ωm). The laboratory results revealed the landslide site is majorly composed of silty sandy clay, silty clay, sandy silty clay, and sandstones as the pre-landslide existing lithologies. The natural water content ranges from 10.6% to 14.0%. The liquid limit ranges from 44.0% to 46.0%, the plastic limit ranges from 15.0% to 17.0%, and the plasticity index from 28.0% to 29.1%. The geophysical and laboratory results revealed consistency in the lithological units in agreement with the characteristic geology of the study area. The landslide site has high gully slope gradients and collects a large volume of floods during the intense rainy season. These soils, during the intense rainfall, imbibe more water, following their high plasticity slide along the sandstone to activate the soil failure.

An Evaluation of a Marginal Land’s Geological Engineering Properties in Borikiri Sandfill, Port Harcourt Nigeria

Aim: The aim of this study was to assess the geological engineering properties of a marginal land in Borikiri Sandfill, Port Harcourt, Nigeria, using both field and laboratory investigations.
 Study Design: The study design involved the drilling of 4 boreholes and standard penetration tests to determine the soil profile and index properties such as particle size analysis, atterberg limits, and moisture content. Consolidation and triaxial tests were also performed to determine the values of the coefficients of permeability (k), volume compressibility (Mv), and consolidation (Cv).
 Place and Duration of Study: The Study was conducted in Borikiri Sandfill, Port Harcourt between February and May 2020.
 Methods: This study's methodology included field research, laboratory analysis, and testing. Drilling and conventional penetration tests were used to assess the soil profile. Laboratory tests such as particle size analysis, atterberg limits, and moisture content were used to determine the index characteristics. The values of permeability (k), volume compressibility (Mv), and consolidation (Cv) were also determined using triaxial and consolidation tests.
 Results: The results of the study showed that the soil profile consists of five stratigraphic sequences, with a top organic silty layer followed by a sandy layer, a dark plastic layer, a dark silty clayey sand, and a well-graded sand. The clays had an average Liquid limit (LL) of 45% and a Plastic Limit (PL) value of 23%. The values of k, Mv, and Cv were determined to be 2.1 x 10-7 m/s, 1.8 x 10-4–2.5 x 10-4 m2/MN, and 3.8 m2/yr, respectively. The average bearing capacity values at 2.5 m and 4.5 m depths were determined to be 186.39 kPa and 278.71 kPa, respectively. Settlement values were calculated empirically for immediate and consolidation settlement, with immediate settlement being high at 25.85 mm and consolidated settlement being 7.53mm. T50 and T90 values were also determined to be 1.32 and 4.52 years, respectively.
 Conclusion: It is recommended that a shallow foundation, down to the first layer, can be used for any light construction on the marginal land in Borikiri Sandfill, Port Harcourt, Nigeria. The values of k, Mv, and Cv also indicate that the soil is relatively compressible, which should be taken into account in any design or construction activities.

Landslide Soil Failure Parameters Characterization Using Geoelectrical Resistivity Methods in Uruagu, Nnewi, Anambra State, Nigeria

Electrical Resistivity Imaging (ERI) and Vertical Electrical Sounding (VES) were deployed over Uruagu landslide area. The main purpose of the geoelectrical resistivity surveys was to characterize the landslide failure parameters in order to identify the soil failure mechanisms. Ten profiles of 2D Electrical Resistivity Imaging (ERI) measuring 200 m each, and thirty Vertical Electrical Sounding (VES), with three VES along each profile, were executed. Nine of the ten profiles were executed within the landslide site while one profile was executed in a residential street as a control profile. Four soil samples were also taken for physical and geotechnical laboratory index analysis. The PASI resistivity meter was used for the geoelectrical resistivity measurements. The Wenner-Schlumberger array was deployed for the ERI with a minimum electrode spacing of 10 m. The Schlumberger array was deployed for the VES with a maximum current spacing of 130 m. ERI resistivity data analysis involved inversion using RES2DINV software package involving mean model residual and construction of iso-apparent resistivity contour maps. VES resistivity data analysis involved calculated parameters from plotted field data on log-log graph then used as initial models in an iterative forward modeling WinResist software package. The results of the ERI and VES for the control profile reveal that the subsurface strata are originally composed of silty clay of resistivity values (16.7 – 60.9) Ωm, clayey silty sand having resistivity values (116 – 800) Ωm and sandstone layer with resistivity values (>814 Ωm). The ERI and VES results for the devastated landslide site reveal counteraction material of resistivity values (>814 Ωm), colluvia and regoliths (116 - 300 Ωm) and variably wet weathered sandstones of resistivity values (<60.9 Ωm). The laboratory results revealed the landslide site is majorly composed of silty sandy clay, silty clay, sandy silty clay and sandstones as the pre-landslide existing lithologies. The natural water content ranges from 10.6% to 14.0%. The liquid limit ranges from 44.0% to 46.0%, the plastic limit ranges from 15.0% to 17.0% and the plasticity index from 28.0% to 29.1%. The geophysical and laboratory results revealed consistency in the lithological units in agreement to the characteristic geology of the study area. The landslide site has high gully slope gradients and collects large volume of floods during intense rainy season. These soils during intense rainfall, imbibe more water, following their high plasticity, slid along the sandstone to activate the soil failure.

Landslide Soil Failure Parameters Characterization Using Geoelectrical Resistivity Methods in Uruagu, Nnewi, Anambra State, Nigeria

Electrical Resistivity Imaging (ERI) and Vertical Electrical Sounding (VES) were deployed over Uruagu landslide area. The main purpose of the geoelectrical resistivity surveys was to characterize the landslide failure parameters in order to identify the soil failure mechanisms. Ten profiles of 2D Electrical Resistivity Imaging (ERI) measuring 200 m each, and thirty Vertical Electrical Sounding (VES), with three VES along each profile, were executed. Nine of the ten profiles were executed within the landslide site while one profile was executed in a residential street as a control profile. Four soil samples were also taken for physical and geotechnical laboratory index analysis. The PASI resistivity meter was used for the geoelectrical resistivity measurements. The Wenner-Schlumberger array was deployed for the ERI with a minimum electrode spacing of 10 m. The Schlumberger array was deployed for the VES with a maximum current spacing of 130 m. ERI resistivity data analysis involved inversion using RES2DINV software package involving mean model residual and construction of iso-apparent resistivity contour maps. VES resistivity data analysis involved calculated parameters from plotted field data on log-log graph then used as initial models in an iterative forward modeling WinResist software package. The results of the ERI and VES for the control profile reveal that the subsurface strata are originally composed of silty clay of resistivity values (16.7 – 60.9) Ωm, clayey silty sand having resistivity values (116 – 800) Ωm and sandstone layer with resistivity values (>814 Ωm). The ERI and VES results for the devastated landslide site reveal counteraction material of resistivity values (>814 Ωm), colluvia and regoliths (116 - 300 Ωm) and variably wet weathered sandstones of resistivity values (<60.9 Ωm). The laboratory results revealed the landslide site is majorly composed of silty sandy clay, silty clay, sandy silty clay and sandstones as the pre-landslide existing lithologies. The natural water content ranges from 10.6% to 14.0%. The liquid limit ranges from 44.0% to 46.0%, the plastic limit ranges from 15.0% to 17.0% and the plasticity index from 28.0% to 29.1%. The geophysical and laboratory results revealed consistency in the lithological units in agreement to the characteristic geology of the study area. The landslide site has high gully slope gradients and collects large volume of floods during intense rainy season. These soils during intense rainfall, imbibe more water, following their high plasticity, slid along the sandstone to activate the soil failure.

Sustainable Alternative for the Production of Soil Cement Bricks

The construction industry plays a fundamental role in the economy of a developing country, representing, in most of them, approximately 3.7% to 10.5% of its Gross Domestic Product. However, it is extremely important to search for sustainable alternatives in this sector, aiming to reduce the environmental impacts generated by the production of inputs, waste generation, in addition to the inappropriate disposal of this activity in the environment. Therefore, the work aimed to evaluate the technical and economic feasibility of the incorporation of residues (Marble and Granite Cutting Waste—MW and Construction and Demolition Waste—CDW) in the production of soil cement bricks (SCB). For the development of the present work, physical and mechanical characterization of the soil, residues (CDW and MW), composites (Control, MW15%, MW25%, MW50%, MW100%, MW30%CDW70%) were performed. After manufacturing the bricks, the characterizations mentioned were carried out at 7, 28 and 60 days, in addition to the evaluation of the geometric characteristics, water absorption and strength of the bricks and microscopic analysis of the post-rupture fragments. Additionally, a cost analysis of the use of SCB was performed compared to two different construction systems (ceramic brick and concrete block). From the results of physical characterization, soil was classified as clayey-silty sand (SC-SM), while the CDW was well-graded sand and MW as sandy clay. Soil and composite plasticity characteristics ranged from weakly plastic (MW15% and MW30%CDW70%) to highly plastic (MW100%). In the compaction tests, composites with the addition of MW presented increasing values in terms of optimal moisture. The compressive strength test performed showed satisfactory results for all composites, especially for MW25%, which obtained the most significant result with 13.777 kPa at 28 days. Thus, it is concluded that the incorporation of CDW and MW for the production of SCB represents a sustainable application for civil construction.

Analysis of transient seepage through a river embankment by means of centrifuge modelling

Earthen river embankments are typically in unsaturated conditions during their lifetime and the degree of saturation within their bodies may vary significantly throughout the year, due to seasonalfluctuations of the river stage, as well as infiltrations of meteoric precipitation and evapotranspiration phenomena. Given the significant effects of partial saturation on the hydro-mechanical behaviour of soils, realistic assumptions on the actual water content distribution inside the embankments are essential forproperly modelling their response to hydraulic loadings. In this framework, centrifuge modelling is a useful tool to get insights into the evolution of saturation conditions of a water retaining structure during flood events. It allows for the direct observation of the groundwater flow process, which is hardly detectable at the prototype scale, enabling, at the same time, the validation and calibration of predictive numerical tools.In this paper, the results of a centrifuge test carried out on small-scale physical model of a compacted silty clayey sand embankment subjected to a simulated high-water event, at the enhanced gravity of 50-g, are presented and discussed. The physical model was carefully instrumented with potentiometers, miniaturized pore pressure transducers and tensiometers. Pore pressures and suctions measured during the experiment showed that the stationary flow conditions were reached only after an unrealistic hydrometric peak persistence. It therefore emerges that, for the design and/or the assessment of the safety conditions of a river embankment similar to the one tested, the simplified hypothesis of a steady-state seepage, in equilibrium with the maximum river stage expected could result, in many cases, an excessively conservative assumption.

Soil water retention curves of a silty clayey sand compacted at different dry density

The study of the hydraulic behaviour of compacted soils in partially saturated conditions is essential for understanding the engineering performance of geotechnical structures such as river embankments. The paper presents the results of an experimental study focusing on the effects of the initial water content and dry density on soil water retention curve (SWRC) and volume change of a compacted soil mixture under hydraulic loading. For this purpose, soil specimens compacted at different water contents(dry, wet and optimum water content), chosen on the basis of standard Proctor compaction test, were used. Specimens of a mixture composed of 70% Ticino sand (TS) and 30% Pontida silt (PON) have been tested. This is a heterogeneous mixture of sand and silt, that usually constitute the embankments of tributaries of river Po (Italy). The SWRCs along drying paths were performed by means of evaporation tests starting from the saturated conditions gained in permeameter tests. For the investigation of the change in the void index during the evaporation test, the volume variation of the tested specimens was estimated by means of a calliper and photographic comparison. Changes in the SWRCs are consistent with changes in specimen initial condition while the soil volume change exhibited at the end of evaporation test is always negligible.

Settlement Improvement of Weak Soil of Natural Moisture Content by Using Geogrid Reinforcement Under Different Dynamic Load

One of new method to improve the bearing capacity of weak soil is by using geosynthetic reinforcement materials that has become more common in past 40 years for a number of applications to reduce the cost of maintences by increasing design life. This study concerned with the behavior of weak soil and the amount of settlement that happened when the soil exposed to different weight load with different number of blows . Field and laboratory tests done to calculate soil settlement. For experimental tests a model with dimension (150×75×75cm) has been manufactured, clayey silty sand soil in model exposed to different dynamic weight by using load with ( 4.5kg), load with (7.5kg) and load with (10kg). Each load strick the soil with 9 5 and 10) blows during an experiment for each dynamic load. 12 Laboretory experiments were conductedon 38 test points, 6 experiments done on soil without geogrid and 6 experiments done on soil with geogrid that included 19 test point for each case.
 The experiments tests show that by increasing the weight load and increasing in number of blows settlement increase in both cases ( without and with geogrid). The experiments show that by using geogrid the settlement decrease comparison with the amount of soil settlement without geogrid. By using geogrid and exposed to weight loads ( 4.5, 7.5 and 10kg.) with No. of blows = 5 the average percent in settlement decrease 1.2, 2.1,1.7%) and with No. of blows =10 for the same loads the average percent of settlement decrease (1.8, 2.7, 2.7%).

Estimation of land subsidence potential via distributed fiber optic sensing

Land subsidence is a global phenomenon that derives from natural processes such as auto-compaction and tectonic activity, as well as anthropogenic activities that are exemplified by withdrawal of water, oil or other fluids from the subsurface. Fluid withdrawal-induced subsidence has become a threat in densely populated zones such as coastal areas, especially in this era of growing climate change impacts when hydrological changes may not enable sufficient recharge of aquifers to replenish withdrawn water. It is important to estimate settlement for design of counter-measures: a challenge in areas of complex sedimentary history and geomedia stratification. Herein is presented the methodology and results of configuration of the Logistics Model using measured settlement data to predict future settlement in the coastal town of Tianjin, P.R. China with validation using continuous strata deformation data obtained through borehole distributed fiber-optic sensing. The cumulative subsidence over the October 2017-December 2019 period reached 56 mm with an estimated potential limit of 96 mm, leaving a balance of 42.0% of the total for attainment in the future. Subsidence of the area is estimated to reach the “stability subsidence stage” by 2050. In the G06 borehole depth range of 3.4–18.4 m which comprises clayey silty sand and silty fine sand, the measured deformation accounts for 58.5% of the total while the residual (future) deformation is 37.6% of that total. The depth ranges of 0–3.4 m (shallow stratum) and 18.4–38.4 m (deep stratum) constitute the “priority layer” because the strata are still in the “accelerated subsidence stage” that is characterized by high subsidence rate estimates for the future. Thus, the projected high subsidence rates of the two layers warrant the design and implementation of proactive countermeasures.

Liquefaction susceptibility of beach sand containing plastic fines

Liquefaction of saturated sand containing fines can be triggered due to propagation of seismic waves or by monotonically increasing loads. In such circumstances excess pore-water pressure development results in loss of confinement and decreased intergranular force transfer, leading to strain-softening behaviour. This research assesses the effect of plastic fines on the liquefaction susceptibility of carbonate sand from Famagusta Bay, Cyprus (Mediterranean Region). The study simulates the diverse composition of sand by incorporating varying proportions of silt and clay. Consolidated undrained triaxial compression tests were conducted to analyse the effect of fines on stability/instability, compressibility and location of critical state lines at low-stress levels of 50, 100 and 150 kPa with relative densities of 35% and 70%. Silt and clay fractions (10, 20, 30%) were incorporated into the sand to form a set of mixed soils. Sand and clayey-silty sand (10%) specimens prepared at loose state exhibited flow behaviour whereas diverse behaviour is observed for other soil groups. The prevention of instability can be attributed to the mineralogical nature of fines that amalgamated the soil structure.

Two-Scale Investigation of the Retention Behavior of a Well-Graded Mixed Soil

The hydraulic characterization of mixed compacted soils is helpful for the design of earthworks subjected to drying–wetting cycles. When the mixed soil is well-graded and made of both coarse and fine fractions, its matric suction may also be due to the short-range adsorption phenomena, as for the soil investigated in this research work. A silty–clayey sand was created by a mixing procedure and experimentally investigated at two different scales. Physical modeling of an infiltration process was performed, allowing an inverse numerical analysis to infer the water retention and the hydraulic conductivity functions of the soil, whereas element testing on soil specimens allowed direct determination of the same equations. In the article, problems related to the employed suction measurement techniques have been pointed out and discussed. By this two-scale combined strategy, features of the soil hydraulic behavior, such as the wetting collapse, the shrinkage during drying, and the loop of hysteresis, were also determined.

Effect of Phytoremediation on Compression Characteristics of Silty Clayey Sand Contaminated with Crude Oil

Effect of Phytoremediation on Compression Characteristics of Silty Clayey Sand Contaminated with Crude Oil

Effect of Phytoremediation on Geotechnical Characteristics of Oil Contaminated Sands

ABSTRACT The environmental contaminations occurred by exploration, drilling, extraction, transportation and storage of different substances for using in industries have serious effects on soils and their properties. This research examined the effects of phytoremediation on the removal of total petroleum hydrocarbons (TPHs) and geotechnical properties of a silty clayey sand contaminated by 3%, 5%, and 7% crude oil. Ophiopogon japonicus and Platycladus orientalis were two types of plants used to determine the phytoremediation effects within 30 and 60 days of operation. The scanning electron microscopy (SEM) images indicated that with increase in crude oil content at 0, 30, and 60 days of investigations, the soil particles become more flocculated. Comparison of the soil samples that experienced phytoremediation and without phytoremediation showed that flocculation of the soil particles became less during phytoremediation process. Use of Platycladus orientalis reduced soil flocculation more compared to Ophiopogon japonicus. The test results also showed that the TPHs removal rate using Platycladus orientalis was more than Ophiopogon japonicus. The addition of more crude oil contents caused enhancement of permeability while liquid limit, plastic limit, maximum dry density, optimum moisture content and CBR decreased. Investigation of the geotechnical properties of soil at different crude oil contents in 30 and 60 days of phytoremediation revealed that soil samples that experienced phytoremediation had more CBR and lower permeability compared to other ones without phytoremediation. It was also observed that upon more days of phytoremediation the liquid limit, plastic limit, optimum moisture content and permeability increased while the maximum dry density decreased. Using Platycladus orientalis compared to Ophiopogon japonicus yielded higher liquid limit, plastic limit, maximum dry density, and CBR along with lower optimum moisture content and permeability.

Effect of phytoremediation on the shear strength characteristics of silty clayey sand

Pollution of the environment by crude oil is a global problem that changes the geotechnical properties of soil, including its shear strength. In this study, the effects of phytoremediation of soil contaminated with crude oil have been investigated using Ophiopogon japonicus and Platycladus orientalis. The results of phytoremediation were tested at 30 and 60 days of treatment. The results were compared with samples that had not undergone phytoremediation. The soil shear strength parameters were determined using unconsolidated undrained triaxial compression tests at confining pressures of 50, 100, and 150 kPa. The results showed that an increase in the crude oil content led to a decrease in deviatoric stress at failure associated to an axial strain level of 20%. The deviatoric stress in the treated samples was about 15% higher than the samples without phytoremediation. The internal friction angle and cohesion decreased as the crude oil content increased. This decrease was less in the remediated samples, especially those exposed to P. orientalis. The results of the triaxial compression tests revealed the positive effect of phytoremediation in reducing the negative effects of crude oil on the soil shear strength characteristics. SEM images of the contaminated soil samples showed that soil flocculation initially increased with an increase in the crude oil content and time and then decreased subsequent to the application of phytoremediation.

Life cycle environmental assessment of retaining walls in unsaturated soils

Retaining structures above groundwater level support soils that are usually in a state of partial saturation and subject to the actions of atmospheric agents. The current design approach considers the possible extremes of soil conditions – either totally dry or totally saturated – but it neglects matric suction’s contribution to soil shear strength. This work aims to describe how unsaturated-soil mechanics of can positively influence the sustainability of retaining structures through a holistic, multidisciplinary, geotechnical, and environmental analysis. The geotechnical analysis allows to estimate the lateral earth pressure of a geostructure in both unsaturated and extreme soil conditions (dry or saturated), which will directly influence the geometrical dimensions of the geostructure. Next, the environmental analysis is performed with the standardized and globally applied Life Cycle Assessment (LCA) tool, in order to quantify the potential environmental impacts of the retaining structure according to both a life cycle and a multi-criteria perspective. First, an LCA model is built for a cantilever retaining wall according to two design approaches: (a) an unsaturated design approach (UDA), i.e. when unsaturated soils’ principles are considered in the design procedure, and (b) a conventional design approach (CDA), i.e. if soil is considered dry or saturated. Three different types of retained soil (i.e. fine-grained soil, volcanic ash, and coarse-grained soil) are considered. Then, the associated environmental impacts on climate change, human health, ecosystems and resources are calculated for the two design approaches. Their comparison allows to quantify the potential reductions in environmental damages provided by the adoption of unsaturated-soil mechanics. The presented case study shows a high potential reduction in environmental impacts for retaining walls interacting with fine-grained soils (silt), lower potential environmental benefits with volcanic ash (clayey–silty sand), but no environmental gain for interaction with a coarse-grained soil (sand) compared to a conventional design approach considering extreme soil conditions.

Evaluation of Dynamic Soil Properties for Alluvial Plain of Bejaia Using Field Data and Laboratory Tests

This paper deals with the evolution of the shear modulus G and the damping D as a function of the shear deformation of the soil, using data from field and laboratory tests. The studied experimental site is located in port area of the city of Bejaia (Algeria), which has already been the subject of numerous geotechnical and geophysical investigation campaigns as part of construction of important industrial projects. In a first step, the geological, tectonic and hydrological contexts of the region are described, as well as the results of the geophysical and geotechnical tests. The result of this first step is the development of a database from field and laboratory tests. In a second step, monotonic and cyclic triaxial tests are performed to identify the dynamic properties on a reconstituted silty clayey sand soil in the laboratory with a characteristic relatively close to the ground in place. In a third step, a numerical analysis is carried out using a FLAC2D code. The nonlinear elastic model proposed by Ramberg–Osgood and limited by the Mohr–Coulomb criterion is used. The comparison between the numerical results and the experimental data shows the applicability of the Ramberg–Osgood model to describe the dynamic behavior of muddy silty sand and muddy sands of Bejaia.

Phosphoric acid contaminated calcareous soils: Volume change and morphological properties

Contamination of soils is a critical problem as a result of malfunctioning industries like possible leakage and inferior disposal of wastes. The leakage and spillage of acids infiltrate to the ground and cause swelling of the foundations because of their reaction with the active minerals in the soils. Calcareous soils are widely used in construction. Hence, the carbonate soils are liable to volumetric changes when contaminated with acids. The current work examines the effect of the changes of volume as well as the microstructure of calcareous soils when infiltrated by different concentrations of phosphoric acid. The samples of soil were equipped with molds of acid resistance high-density polyethylene. The volume change was measured by the linear variable differential transformer. The compositional analysis was performed for the acid-contaminated samples. The results indicate there is a volume change with varying the acid concentration, however, silty clayey sand exhibited extensive expansion. This can be attributed to the severe reactions of phosphoric acid and carbonate mineral and the products blocked off the passage for the acid to permeate to the other parts of the soil sample as evidenced by the morphological and compositional analysis of the contaminated samples.