Soil Improvement Technology Research Articles

Improving internal erosion resistance of silty sand using additives

Seepage-induced erosion, leading to piping, is one of the most common causes of failure for earth dykes, levees and dams. Various soil improvement (mixing) technologies can be employed to improve the internal erosion resistance of more troublesome soils. This paper describes the first steps in demonstrating nanoclay (montmorillonite) additive as a sustainable alternative to traditional soil additives for erosion-control applications. In this regard, the erodibility characteristics of standard Proctor (SP) compacted, very silty sand amended with 0·5–6% dry weight montmorillonite K10 (MK10) material was investigated at bench scale using the hole-erosion test (HET) apparatus. Parallel testing was performed on the same soil amended with 0·25–3% cement for comparison. Substantial erosion resistance improvements were achieved for as little as 0·5–1% MK10 content, comparable to cement addition, with the HET classification increasing from HET groups 1–2 for the highly erodible, compacted, very silty sand investigated to HET group 4 (moderately slow erosion) for the 1% MK10–soil mixture. Further investigations indicated the erosion resistance classification of the improved soil was not altered for under-compaction that achieved only 80% SP maximum dry density or for compaction at ± 2 percentage points from the identified SP optimum water content.

Engineering behaviour of MICP treated marine clays

In the present scenario, with much focus on sustainable development worldwide, Microbially Induced Calcite Precipitation (MICP) is a promising biological soil improvement technology. However, only very limited research is reported on the effectiveness of this technique in marine clays. This paper presents the salient features of an experimental study conducted on two typical marine clays stabilised by MICP. Effectiveness of the technique was evaluated through a series of one-dimensional consolidation tests, unconfined compression tests, and index property determinations. It is found that biostimulation approach is not effective in marine clay; bio-augmentation is needed for soil improvement. Bio-augmentation results in the reduction of liquid limit and plasticity index to about 29% and 47%, respectively for the marine clays. A comparable improvement in volume change behaviour is also observed. There is a marked increase in undrained shear strength, upto about 148%, of MICP treated marine clays at toughness limit water content. Curing is also found to have a significant role in soil improvement. The observed transition in the nature of the tested marine clays from that of fat clay to elastic silt suggests the potential of the proposed approach. An empirical equation is also proposed to predict compression index of MICP treated marine clays.

Review on the Crop Straw Utilization Technology of China

China is an large agricultural country, which grain output has been among the highest in the world. In recent years, agricultural waste caused by high grain yield has attracted more and more attention. As one of the main agricultural waste, the total straw amount of China has reached 870 million tons by year of 2019, and the straw utilization amount has reached 730 million tons, which indicates enormous strains on the environment. In China, straw burning is strictly forbidden by local governments, so it is mostly utilized by returning the field, making manure, fodder, fuel, base stock or raw material. The five utilization ways separately make up 61.3%, 5.3%, 14.9%, 10.3%, 0.8%, 1.0% of the total share. To promote better utilization of straw, this paper made a comprehensive review of the main utilization technologies in China by the method of literature research. According to the research, the utilization technologies of straw mainly include corn straw deep tillage technology, cotton straw deep-turning technology, wheat straw mulching-corn straw rotating tillage technology, less no-tillage straw mulching technology, rice-wheat (or rape) straw crushing returning rotary tillage technology, straw rapid maturing, straw-forage-fertilizer planting and raising combination technology, straw-biogas-fertilizer energy ecological technology, straw-bacteria-fertilizer substrate utilization technology, straw-carbon-fertilizer returning and soil improvement technology. All these utilization have promoted the rapid development of the comprehensive utilization of straw in China, and enlightened further development of straw utilization.

Mathematical modelling and simulation of microbial carbonate precipitation: the urea hydrolysis reaction

Microbial carbonate precipitation is expected to play a major role in next-generation soil improvement technologies. To date, research into this method has relied on experimental and/or observational approaches. However, in order to understand the long-term effects of microbial carbonate precipitation and apply these to real environments, it is necessary to employ a predictive approach to determine the future state of the soil when using this soil improvement method. In this work, a mathematical model and numerical simulations based on the reaction–diffusion system for the microbial urea hydrolysis reaction are proposed. These techniques may be used to provide the spatiotemporal precipitation patterns of carbonates between soil particles and the particle surfaces. The simulation results revealed that the characteristic precipitation patterns depend on the diffusion of carbonates caused by the microbial urea hydrolysis reaction, and there was a significant shift in the amount of carbonate from a dissipated state into an equilibrium state.

Better Together: Water Treatment Residual and Poor‐Quality Compost Improves Sandy Soil Fertility

Water treatment residual (WTR) is an underused clean water industry byproduct, generally disposed to landfill. This study assesses the benefits and risks of ferric‐WTR as a soil amendment or co‐amendment for plant growth in a nutrient‐poor sandy soil. A 12‐wk pot trial tested the efficacy of WTR and a locally available, low‐quality, municipal compost as single (1, 5, and 12.5% dry mass) and co‐amended treatments (1:1 WTR/compost ratio, at 2, 10, and 25%) on wheat (Triticum aestivum L.) growth in a sandy soil. The low total N content of the compost and low WTR P and K contents resulted in significantly lower (up to 50% lower, p < 0.05) plant biomass in single amendments compared with the control, whereas the highest co‐amendment produced significantly higher plant biomass (33% higher, p < 0.05) than the control. This positive co‐amendment effect on plant growth is attributed to balanced nutrient provision, with P and K from the compost and N from the WTR. Foliar micronutrient and Al levels showed no toxic accumulation, and co‐amended foliar Mn levels increased from near deficient (20 mg kg−1) to sufficient (50 mg kg−1). Total WTR metals were well below maximum land application concentrations (USDA). Trace element bioavailability remained the same (Ni, Cu, and Hg) or significantly decreased (B, Al, Cr, Mn, Fe, Zn, As, and Cd; p < 0.05) during the pot trial. These results suggest, within this context, that a WTR–compost co‐amendment is a promising soil improvement technology for increasing crop yields in sandy soils.Core Ideas Iron (Fe) water treatment residual (WTR) is a byproduct of potable water production. Wheat biomass increased by 33% when poor‐quality compost and Fe‐WTR were combined. Combined amendments and control outperformed single amendments of compost and WTR. Bioavailable metals measured after the pot trial did not increase. Co‐application of compost with WTR may counter the negative effects of P sorption.

The State of Soil Improvement in China: The G-I Soil Improvement Committee’s China Scan Tour

During the last four decades, China has made significant improvement in various sectors of its infrastructure, including high-speed railways, long-span and cross-sea bridges, large dams, long- and large-diameter tunnels, and land reclamation. Many new soil-improvement technologies have been successfully developed, improved, and implemented on these major projects.

An environmentally friendly soil improvement technology for sand and dust storms control

Background: Dust storms occur when unchecked, strong, or turbulent winds combine with exposed loose and dried soil surfaces. Sand and dust storms have a significant impact on society, economy, and environment at local, regional, and global levels. The environmental and health hazards of such storms cannot be permanently reduced, however, by taking appropriate measures, its impact can be reduced. The present study aimed to investigate the effects of microbial precipitation of calcium carbonate (CaCO3) as a biocompatible agent on soil stabilization and control of dust storms using ureaseproducing bacteria (UPB) as a biological improvement technique, which were isolated, identified, sprayed on the soil surface. Methods: For this purpose, the erosion of bio-cemented soil samples was investigated experimentally in a wind tunnel under the condition of wind velocity of 0 to 98 km.h-1 in two soil types with sandy and silty texture in a completely randomized design with three replicates. Results: The investigation of the threshold wind velocity of soil particles showed that soil particles began to move at velocity of 8 and 10 km.h-1 in silty and sandy soils, respectively, but in all biological samples (MICP), particles did not move until the wind speed reached 97 km.h-1. It was also revealed that the weight loss of all MICP-treated samples at different wind velocities was significantly reduced compared to the control group. Differences in the amount of soil loss among bio-cemented samples and control treatments were even superior at higher velocities, so that at velocities more than 57 km.h-1, soil losses increased significantly in the control group, while in soils treated with bacteria, soil loss was very low (about 2.5 kg.m-2.h-1). Comparison of the bacteria used in this study also showed that Bacillus infantis and Paenibacillus sp3 had high efficiency in controlling dust storms. Conclusion: The formation of abrasion-resistant surface layers on soil samples treated by biocementation showed that cementation by biological methods could be an effective way to stabilize surface particles and control sand and dust storms.

Consolidation analysis of an impervious multi-pile composite ground under rigid foundation

The multi-pile composite ground with fully penetrated long rigid piles and partially penetrated impervious or pervious short piles is a new type of soft soil improvement technology. Based on the equal vertical strain assumption, the governing equations for average excess pore water pressures within the surrounding soil of the composite ground with long rigid piles and impervious short piles are derived under ramp loading. The corresponding analytical solutions are developed based on the one dimensional consolidation theory of a double-layer ground, and overall average degree of consolidation of the composite ground is presented. The accuracy of the proposed solution is examined by FEM. A parametric study on the consolidation behaviour of the composite ground is performed using the proposed solutions. The results show that the consolidation rate of the composite ground increases with increasing the constrained modulus and the area replacement ratio of the long piles. In addition, it increases with increasing the modulus ratio of the subsoil below short piles to that above the tip of the short piles. The variations of the length, the constrained modulus and the area replacement ratio of the impervious short piles have negligible influence on the consolidation rate of the composite ground.

Bisphenol S Adsorption Behavior on Ferralsol and Biochar Modified Soil with Dissolved Organic Matter.

Bisphenol S (BPs) has been found in a variety of common consumer products surrounding human living, despite the fact that it could damage the human digestive system and genital system. In China, straw-returning to the field is a common soil improvement technology used to increase the concentration of dissolved organic matter (DOM), which plays an important role in the natural environment as a microreactor of contaminants. Additionally, the biochar obtained by the straw is an effective soil conditioner. DOM is a key influencing factor when biochar is employed as the conditioner of BPs contaminated soil. However, the BPs adsorption behavior on the Ferralsol affected by DOM and biochar is also unclear. Hence, DOM was prepared and the effect of DOM on the BPs adsorption behavior on soil and biochar modified soil was investigated. DOM was characterized by Elemental analysis, Fourier transforming infrared spectra (FT-IR), and three-dimensional excitation-emission matrix spectra (3D-EEM). The results of the adsorption experiments indicated that both biochar and DOM could improve the BPs adsorption capacity in Ferralsol, while DOM suppressed the BPs adsorption capacity of biochar modified soil, indicating that DOM and BPs could not be applied at the same time for BPs adsorption.

Soil Improvement Technology - Cement Deep Mixing Method

Soil Improvement Technology - Cement Deep Mixing Method

Experimental study on the effect of grouting interval on microbial induced calcium carbonate precipitation

Microbial induced calcium carbonate precipitation is a kind of environmentally friendly soil improvement technology. Microbial induced calcium carbonate precipitation reaction needs to enhance microorganism and nutrient solution containing urea and calcium salts. Different grouting intervals will get different curing effects.. In this paper, the effect of bio-cemented sand under different grouting time intervals was analyzed from the macroscopic physical and mechanical properties and micropore structures through the soil test and the electron microscope scanning test of the bio-cemented sand. The experimental results show that: with the increase of grouting time interval, the effect of bio-cemented sand was first increased and then decreased, and the 8h was the turning point of trend change. When the time interval was 8h, the permeability coefficient, water absorption, dry density, unconfined compression strength and calcium carbonate content reached 1.79E-04m/s, 18.88%, 1.67g/cm3, 0.90MPa and 3.49%, respectively. The scanning pictures show the calcium carbonate precipitation effectively bonded sand particles. The apparent pore content and the average pore diameter under the 8h of the time interval was 12.66% and 43.690 μm respectively, which was smaller than that of the others.

Effects of soil improvement technology on soil quality in solar greenhouse.

Currently, cucumber cultivation is mainly through monoculture, as continuous culture leads to the decrease of crop yield and soil quality. In order to improve soil quality to achieve continuous monocultures, soil physicochemical properties, microbial biomass, content of phenolic compounds, and the size of bacterial, fungal, ammonia-oxidizing bacteria (AOB), and Fusarium oxysporum were first evaluated in cucumber monoculture solar greenhouse. Soil improvement technology, including catch wheat (CW), calcium cyanamide disinfection (LN), and straw reactor technology (SR) during summer fallow period, was compared with conventional fallow (CK). Results showed that CW, LN, and SR all significantly increased soil pH, and LN and SR increased soil electrical conductivity (EC); however, CW decreased soil EC. Meanwhile, LN increased soil available N content significantly and SR increased available P content significantly. CW had negative effect on the accumulation of soil available nutrients, conversely, CW and SR had positive effect on the accumulation of microbial biomass carbon (MBC). All the treatments increased the total phenol content in the soil compared with CK. While CW increased the size of bacteria, AOB in the soil inhibited fungal and wilt pathogen size. LN also increased the size of soil bacteria and reduced the size of fungi. The comprehensive evaluation of all treatments showed that CW could control soil nutrient loss and improve the continuous cropping soil, making the soil transform from fungi to bacteria type. All the treatments accelerate the accumulation of phenolic compound, while whether or not developing autotoxicity requires further investigation.

Distributed Agency Between 2D and 3D Representation of the Subsurface

Although severely altered, the urban subsurface is the base of the natural system, and is crucial for a stable, green, healthy, and liveable city. It is also the technical space, the engine room of the city where vital functions such as water, electricity, sewers, and drainage are located. This hybrid state needs to be recognized when designing resilient and durable (subsurface) infrastructure within urban renewal projects, so as to properly employ the parameters of both natural and technical systems. Interdisciplinary work is needed in order to be able to link natural systems (a) the water cycle, (b) soil and subsurface conditions, (c) soil improvement technology, and (d) opportunities for urban renewal (e.g. urban growth or shrinkage) in an efficient way. The importance of implementing “boundary spanning” when doing interdisciplinary work that deals with the effects of climate change is a widely recognized method, and has been an object of study in the city of Rotterdam in the past decade. The particular need for a “distributed agency” became clear during several research projects dealing with climate change, because it enables different actors to contribute to the development of the project at different phases. The representation of the city as both a natural and technical construction has been tested through the use of 2D and 3D information, which has played a significant role in enabling designs to incorporate the dimension of the subsurface. 2D and 3D information needs to anticipate different scales of specific planning and/or design phases, and they must also address various topics of the subsurface. For each phase of urban development, the distributed agency between 2D and 3D information is investigated and reflected upon. Conclusions are then drawn on the relationship between 2D and 3D information, and how it could relate in a productive, boundary spanning act that is inclusive of the subsurface. Based on these potential connections, the design of a new concept which implements boundary spanning as a facilitator is presented.

Diversity of Sporosarcina-like Bacterial Strains Obtained from Meter-Scale Augmented and Stimulated Biocementation Experiments.

Microbially Induced Calcite Precipitation (MICP) is a biomediated soil cementation process that offers an environmentally conscious alternative to conventional geotechnical soil improvement technologies. This study provides the first comparison of ureolytic bacteria isolated from sand cemented in parallel, meter-scale, MICP experiments using either biostimulation or bioaugmentation approaches, wherein colonies resembling the augmented strain ( Sporosarcina pasteurii ATCC 11859) were interrogated. Over the 13 day experiment, 47 of the 57 isolates collected were strains of Sporosarcina and the diversity of these strains was high, with 20 distinct strains belonging to 5 species identified. Although the S. pasteurii inoculant used for augmentation was recovered immediately after introduction in the augmented specimen, the strain was not recovered after 8 days in either augmented or stimulated soils, suggesting that it competes poorly with indigenous bacteria. Past studies on the physiological properties of S. pasteurii ATCC 11859 suggest that close relatives may have selective advantages under the biogeochemical conditions employed during MICP; however, the extent to which these properties apply to isolates of the current study is unknown. Whole cell urease kinetic properties were investigated for representative isolates and suggest up to 100-fold higher rates of carbonate production when compared to other biomediated processes proposed for MICP.

Investigating the Influence of Various Stormwater Runoff Control Facilities on Runoff Control Efficiency in a Small Catchment Area

Urbanization causes an increase in the flood discharge because of the infiltration capacity. Furthermore, extreme precipitation events have been an increasing concern for many regions worldwide. This study aimed to investigate the influence of different outflow control facilities on runoff reduction in a small watershed. We focused on the soil-improvement technology and rainwater tanks as outflow control facilities and conducted a runoff calculation using a rainfall event of a magnitude that is likely to occur once in a hundred years. The calculation showed that the soil-improvement technology reduced runoff during long-term continuous rainfall, whereas in a concentrated short-term rainfall event, a significant difference in the runoff reduction effect between rainfall tanks of various volumes was observed. Since effective countermeasures for runoff reduction differ depending on the rainfall distribution pattern, we suggested both facilities for storing initial rainfall and initiating countermeasures for penetration improvement over the long term.

Numerical Modelling of Rayleigh Wave Propagation in Course of Rapid Impulse Compaction

As the soil improvement technologies are the area of a rapid development, they require designing and implementing novel methods of control and calibration in order to ensure the safety of geotechnical works. At Wroclaw University of Science and Technology (Poland), these new methods are continually developed with the aim to provide the appropriate tools for the preliminary design of work process, as well as for the further ongoing on-site control of geotechnical works (steel sheet piling, pile driving or soil improvement technologies). The studies include preliminary numerical simulations and field tests concerning measurements and continuous histogram recording of shocks and vibrations and its ground-born dynamic impact on engineering structures. The impact of vibrations on reinforced concrete and masonry structures in the close proximity of the construction site may be destroying in both architectural and structural meaning. Those limits are juxtaposed in codes of practice, but always need an individual judgment. The results and observations make it possible to delineate specific modifications to the parameters of technology applied (e.g. hammer drop height). On the basis of numerous case studies of practical applications, already summarized and published, we were able to formulate the guidelines for work on the aforementioned sites. This work presents specific aspects of the active design (calibration of building site numerical model) by means of technology calibration, using the investigation of the impact of vibrations that occur during the Impulse Compaction on adjacent structures. A case study entails the impact of construction works on Rayleigh wave propagation in the zone of 100 m (radius) around the Compactor.

Field and laboratory performance of a cold-region sand stabilized with geofiber and synthetic fluid

This paper presents results from a case study on the improvement of a poorly graded sand through treatment with geofiber and synthetic fluid. The soil improvement technology was applied in the field at a site near Barrow, Alaska. The treatment at dosages of 0.25% geofiber and 1% synthetic fluid was effective and met design requirements based on tests conducted shortly after the completion of the stabilization process. However, after going through a full freeze-thaw cycle, some deterioration in load bearing characteristics was encountered. Field CBR and soil stiffness tests were performed to quantify the strength loss in the soil. Additionally, an extensive and systematic laboratory testing program was implemented to investigate and evaluate the treatment dosages of the additives used. The laboratory tests evaluated each of the additives independently, as well as for their combined use. The best performance in the laboratory was obtained from samples containing 0.35% geofiber and 2% synthetic fluid. Freeze-thaw tests were performed on various compositions of treatment to study the potential factors responsible for the loss of strength encountered in the field. When subjected to freeze-thaw, samples experienced significant decrease in CBR performance. Also, a group of tests on cured samples were conducted to evaluate the time-dependency of soil treatment. The field dosage rates did not show any improvement with curing, however other treatment compositions indicated slight to moderate increase in CBR performance due to curing.

Development of a Scaled Repeated Five-Spot Treatment Model for Examining Microbial Induced Calcite Precipitation Feasibility in Field Applications

Microbial induced calcite precipitation (MICP) has been heavily investigated in laboratory experiments with few forays into field-scale implementation. Conventionally, MICP refers to an alternative technology for improving the geotechnical properties of soils via microbially mediated urea hydrolysis inducing conditions for calcite precipitation at particle contacts. The study presented herein focuses on up-scaling the conventional treatment process to more realistic volumes through the development of a scaled repeated five-spot treatment model. Commonly used in oil recovery applications, the repeated five-spot well pattern provides for a flow symmetry condition allowing for improved laboratory model feasibility. A conventional MICP two-phase treatment technique resulted in improvement in the target treatment (0.5 m by 0.5 m by 0.15 m) zone with small spatial variation. Sensors, including bender elements and sampling wells, provided valuable insight into the evolution of biological, chemical, and mechanical changes spatially and temporally during treatment. Overall, the scaled repeated five-spot treatment model was successful at capturing a complex treatment scenario involving a bio-mediated soil improvement technology and demonstrated the potential to capture complex scenarios of soil improvement.

An Environmentally Friendly Soil Improvement Technology with Microorganism

Cement or lime is generally used to improve the strength of soil. However, bacteria were utilized to produce cementation of loose soils in this study. The microo rganism called Bacillus, and <TEX>$CaCl_2$</TEX> was introduced into loose sand and soft silt and <TEX>$CaCO_3$</TEX> in the voids of soil particles were produced, leading to cementation of soil particles. In this study, loose sand and soft silt typically encountered in Korea were bio-treated with 3 types of bacteria concentration. The cementation (or calcite precipitation) in the soil particles induced by the high concentration bacteria treatment was investigated at 7 days after curing. Based on the results of Scanning Electron Microscope (SEM) tests and EDX analyses, high concentration bacteria treatment for loose sand was observed to produce noticeable amount of <TEX>$CaCO_3$</TEX>, implying a significant cementation of soil particles. It was observed that higher calcium carbonate depositions were observed in poorly graded distribution as compared to well graded distribution. In addition, effectiveness of biogrouting has also been found to be feasible by bio-treatment without any cementing agent.

Study on Soil Improvement Technology of EPBS Tunnel

The tunnel construction often encounters the problem of adaptability of sand-gravel formation and earth pressure balance shield (EPBS) construction, which has brought new technical problems and challenges to those who are participating in the construction project. In order to ensure the normal operation of shield construction, the soil must have ideal plasticity and liquidity, and low permeability to intercept groundwater. Therefore, we must adopt the soil improvement techniques ,namely, to inject the modified materials (mud, foam, polymer, etc.) into excavation face and earth pressure tank(if necessary, to the screw conveyor) to ensure the stability of excavation face, achieve EPBS driving, and help to reduce mechanical load, reduce land subsidence, and increase driving speed at the same time. The ground improvement technique is an important part of the EPBS method. The quality of the application of soil improvement technology is very important to maintain the stability of excavation face and the screw dump device’s dumping smoothly. It also has a significant impact on the shield machine’s functioning safely,economically and efficiently.