The Impact of Using Different Types of Soft Soils Treated by Stone Columns on Creep Behavior

The stone column technique is an effective method to increase the strength of soft cohesive soil, which results in a reduction in foundation settlement and an increase in bearing capacity. The topic of restraining creep settlement through the use of stone columns techniques has gained increasing attention and consideration; because stone columns are widely used to treat soft soil deposits, caution should be applied in estimating creep settlement. We discovered a reversible relation between shear parameters and the creep settlement in floating stone columns; while, in case of end-bearing stone columns shows a direct positive relation between shear parameters and the creep settlement, and the creep settlement began at the primary settlement. The shear parameters affected the improvement factor (n) of creep settlement in both floating and end-bearing stone columns. The standard creep coefficient’s n values in floating and end-bearing conditions were more significant than the low creep coefficient’s n values in forwarded geometric conditions. The stress in both floating and end-bearing stone columns was increasing and uniformly distributed along the length of the floating stone column and in the case of end-bearing stone column was limited to the stiffness layer; the maximum vertical stress was in the central point of the embankment. The embankment’s maximum horizontal displacement occurred on the edge.

State-of-the-Art Review of Enzyme-Induced Calcite Precipitation (EICP) for Ground Improvement: Applications and Prospects

The global construction industry consumes huge amounts of mined materials that are considered unsustainable for earth resources. In addition, Portland cement which is a key element in concrete and most construction materials is considered one of the main contributors to worldwide CO2 emissions. On the other hand, natural cemented soil deposits are examples of sustainable structures that have survived decades of severe environmental conditions. Mimicking these natural biological systems provide an alternative to the current practices of construction materials production. Enzyme-induced carbonate precipitation (EICP) is a bio-inspired technique based on the precipitation of calcium carbonate for enhancing the geo-mechanical properties of soils. In this technique, calcium carbonate acts as a cementitious agent that binds the soil particles together at the points of contact, hence, increasing the strength and stiffness of treated soils, while relatively reducing the soil permeability and porosity. The achieved enhancements make EICP useful for applications such as ground improvement, construction materials, and erosion control over traditional binders. This paper presents a state-of-the-art review of EICP for ground improvement including the fundamental basics of EICP treatment. The paper also discusses the chemical and physical factors affecting the performance of EICP such as enzyme source, enzyme activity and solution constitutes. Moreover, the paper reviews the different methods and testing techniques used in the application of EICP for soil treatment. Furthermore, the paper compares EICP with other biomineralization techniques in terms of performance and applicability on ground improvement. Finally, the paper discusses the research gaps and existing challenges concerning the commercialization and large-scale implementation of the technology.

Evaluation of the Effectiveness of a Soil Treatment Using Calcium Carbonate Precipitation from Cultivated and Lyophilized Bacteria in Soil’s Compaction Water

Microbial-induced carbonate precipitation (MICP) is a bio-inspired solution where bacteria metabolize urea to precipitate. This carbonate acts as a bio-cement that bonds soil particles. The existing framework has focused mainly on applying MICP through infiltration of liquid bacterial solutions in existing soil deposits. However, this technique is inefficient in soils with high fines content and low hydraulic conductivity, and thus few studies have focused on the use of MICP in fine soils. The main objective of this study was to evaluate the effect of MICP applied to compaction water in soils containing expansive clays and sandy silts. This approach searches for a better distribution of bacteria, nutrients, and calcium sources and is easy to apply if associated with a compaction process. In soils with expansive minerals, the effect of MICP in swelling potential was explored at laboratory and field scales. In sandy silts, the evolution of the stiffness and strength were studied at the laboratory scale. The treatment at the laboratory scale reduced the swelling potential; nevertheless, no significant effect of MICP was found in the field test. In sandy silts, the strength and stiffness increased under unsaturated conditions; however, subsequent saturation dissolved the cementation and the improvement vanished.

Comparison of Invasive and Non-Invasive Methods in Site Response, Case Study: Soil Deposits of La Estrella

A great part of the Colombian territory is under medium to high seismic hazard due to the complex tectonic condition, which in turn affects, particularly, areas where the population density is highest. A response spectrum analysis of the ground is currently required by seismic design codes for site response analysis. For this, the shear wave velocity (Vs) profile must be established. The use of seismic invasive methods such as Down Hole or Cross Hole for the determination of the shear wave velocity (Vs), has been typically recommended. In recent years, significant progress has been made in non-invasive seismic methods such as MasW (Multichannel Analysis of Surface Waves) and ReMi (Refraction Microtremor), in order to estimate the Vs profile from surface waves analysis. Due to the accessibility and low cost, these methods represent a viable alternative to determine the profile of Vs. In this project, the seismic response of soil deposits was evaluated in the La Estrella municipality located in the south of The Aburrá Valley. One-dimensional (1D) models were simulated by characterizing the soil profile through the shear wave velocity with MasW and ReMi seismic tests. The results were compared with models based on shear wave characterization through Down Hole methods. The 1D response spectrums were determined with an equivalent linear model in DEEPSOIL and GTS NX software. The resulting spectra were compared through relative difference and correlation coefficient. Final results demonstrated that the spectra present low relative differences for long periods, moderate relative differences for moderate periods, and low to moderate relative differences for short periods. The general correlation coefficients were 0.6. This was evidence that non-invasive seismic methods allow an appropriate response spectrum analysis.

Effect of sprayer parameters and wind speed on spray retention and soil deposits of pesticides: Case of artichoke cultivar

Irrational use of chemical method for crop protection, presents increasingly serious risks for human health and the environment. Droplet size and meteorological parameters are key factors to both environmental contamination and pest control efficacy. The objective of this study is to assess the impact of the nozzle use parameters, the operating pressure and the wind speed on droplet foliage deposition (retention) and soil deposition (losses), when treating artichoke. Several combinations were tested in a wind tunnel and in the field, under Mediterranean microclimatic conditions, using a fluorescent dye as a substitute for pesticide. Multiple regression models were built from tunnel data to predict foliage deposition and soil deposits, with determination coefficients of 0.96. Thus, models are able to simulate pesticide deposition on artichoke leaves and soil deposition, depending on sprayer parameters and wind speed. Foliage deposition and soil deposits rates ranged from 30 to 52% and 26 to 57% respectively for anti-drift nozzle. For conventional nozzle, rates varied from 20 to 38% and 31 to 62%. To improve retention and reduce spray losses, it is recommended to choose a medium droplet size when using an anti-drift nozzle, in conjunction with medium nozzle size, medium pressure and reduced wind speed.

Structure Features, Damage and Treatment of Two Pottery artifacts from Tel El-Shobak, Qalyubia, Egypt: Case Study

The research paper aims to identify structure features, damage and treatment of two pottery artifacts from Tell Al-Shobak in Qalyubia, "one of the archaeological sites dating back to new kingdom". Polarized Microscopy "PLM", Scanning Electron Microscope with Energy dispersive X-ray unit "SEM-EDX", X-Ray Diffraction analysis "XRD", and Differential thermal analysis "DTA" were adopted for investigating and analyzing pottery sherds. The research identified structure features proving that the used clay is Nile clay, the additives are sand, grog and calcite. The formation technique is potter wheel .The surface treatment is slip layer. The firing atmosphere is oxidizing. Firing temperature might be about 726.78°C The first pottery vessel and 737.80°C for the second pottery plate. Research also proved that pottery pieces suffer from various damage aspects such as soil deposits, stains, cracking, fracture, loss of some parts, lack of durability, weakness, and salt crystallization. The studied pottery pieces treated using mechanical cleaning method and chemical cleaning using a mixture of acetone and toluene at a ratio of 1:2 respectively to remove clay soil deposits. EDTA applied to remove lime deposits. Hydrogen peroxide20 % was used to remove soot. Nano Silica 1% was applied to strengthen archaeological pottery .Assembling the pottery sherds was done by Paralloid B72 50%. Replacement pottery sherds conducted by Microballoon and grog in a ratio of 2:1, respectively. After treatment, the pottery artifacts were ready for museum display.

Manufacturing of Clayey Bricks by Synergistic Use of Waste Brick and Ceramic Powders as Partial Replacement of Clay

Clay bricks are extensively used as building material worldwide. Natural soil deposits are in constant reduction due to the frequent use of clay to manufacture bricks. About 1600 billion bricks are produced annually by the consumption of millions of tons of natural resources. The prime focus of this study is to assess the feasibility of using a composite mixture of waste brick powder (WBP) and waste ceramic powder (WCP) as a replacement for depleting natural resource “clay” in brick manufacturing. Based upon the previous studies, the replacement levels were kept as (4 + 5)%, (8 + 10)%, and (12 + 15)% of WCP and WBP, respectively. The brick specimens were evaluated in terms of compressive strength, modulus of rupture, density, water absorption, efflorescence, apparent porosity, resistance to chemical attack and sulfate attack, and freeze-thaw resistance. The study reveals that about 27% of clay can be replaced with ceramic waste powder and waste brick powder, which can preserve a massive amount of natural clay without compromising the quality of the bricks.

Post-Collapse Evolution of a Rapid Landslide from Sequential Analysis with FE and SPH-Based Models

Propagation models can study the runout and deposit of potential flow-like landslides only if a reliable estimate of the shape and size of the volumes involved in the phenomenon is available. This aspect becomes critical when a collapse has not yet occurred and the estimation of the unstable volume is not uniquely predictable. This work proposes a strategy to overcome this problem, using two established analysis methods in sequence; first, a Strength Reduction Method (SRM)-based 3D FEM allows the estimate of the instable volume; then, this data becomes an input for a Smoothed Particle Hydrodynamics (SPH)-based model. This strategy is applied to predict the possible evolution of Sant’Andrea landslide (North-Eastern Italian Alps). Such a complex landslide, which affects anhydrite–gypsum rocks and is strongly subject to rainfall triggering, can be considered as a prototype for the use of this procedure. In this case, the FEM–SRM model is adopted, which calibrates using mapping, monitoring, geophysical and geotechnical data to estimate the volume involved in the potential detachment. This volume is subsequently used as the input of the SPH model. In this second phase, a sensitivity analysis is also performed to complete the evaluation of the most reliable final soil deposits. The performed analyses allow a satisfactory prediction of the post-collapse landslide evolution, delivering a reliable estimate of the volumes involved in the collapse and a reliable forecast of the landslide runout.