Properties Of Surrounding Soil Research Articles

Installation effect of rigid inclusions in soft clay improvement

Rigid Inclusions have been increasingly used as a successful technique for improving soft clay deposits. This technique was first introduced by Menard in the 1990s and is known commercially as Controlled Modulus Columns (CMC’s) [1]. Unlike ordinary piles that transfer the entire external loads to the stiffer-bearing soil layers, rigid inclusions are mainly used to reduce the total and differential settlements by reducing the external loads transferred to the soft soil layers. One of the challenging tasks associated with this type of improvement is to reasonably estimate the ground deformations under different loading conditions [2]. Previous research focused mainly on getting reliable estimates of the ground movements and the straining actions acting on the rigid inclusions; however, the importance of the installation effect on the predicted deformations and straining actions was not clearly considered. The current paper aims to develop a realistic approach that takes into consideration the installation effect of rigid inclusions by utilizing the cavity expansion theory to estimate the improvement in the surrounding soil properties and accordingly enhance the accuracy of estimating the deformations and the straining actions. A case study of a zone loading test performed in New Mansoura City, Egypt, is analyzed utilizing the three-dimensional finite element method, taking into consideration the installation effect of the rigid inclusion by applying radial deformations to the soil layers and estimating the enhanced soil parameters particularly the deformation modulus and the over consolidation ratio. Results of the study showed that considering the improved soil parameters results in a better prediction of the settlement values of footings resting on the improved soil compared to the measured values. The average error in the settlement values is reduced from about 74 % to about 24 % after considering the enhancement in the soil parameters due to the installation effect.

Consolidation analysis around cavity expansion in presence of vertical drains

As a ground improvement technique, the new method composed by a cylindrical cavity expansion (CCE) combined with vertical drains (VD) greatly accelerates the consolidation of soft soil. In fact, the cylindrical cavity applies a radial displacement in the soil. Excess pore pressures will be consequently generated and the consolidation process will occur at the vicinity of the cavity wall. The dissipation of excess pore pressures can be enhanced in presence of VD installed at a radial distance rd from the center of the cylindrical cavity. Because of CCE installations in soft soil, surrounding soil properties are altered in such a manner that horizontal permeability of the soil in the smear zone reduces. The purpose of the present paper is to investigate the subsequent consolidation around CCE using the Finite Difference Method (FDM) by taking into account the CCE installation disturbance. Parametric analysis aimed to investigate the effect of the extent of the disturbed zone, the soil permeability reduction in the smear zone on the rate of consolidation around CCE.

Investigating the influence of surrounding soil properties on leakage discharge from cracks in polyethylene pipes

Numerous factors affect the amount of leakage from pipes, e.g. inside pressure, type of pipe failure, soil around the pipe, etc. Few researches have been done on the effect of environment around the pipe on the leakage discharge. In the present study, the leakage from pipes in presence of different soils is experimentally investigated. Leakage from a cracked polyethylene pipe was simulated in the presence of various soils with different properties in a laboratory setup. Leakage- pressure relationships were obtained according to fixed and variable area discharge theory. By quantifying the soil characteristics, the relationship between leakage- pressure coefficients (m and Cd) and soil parameters was obtained. It was concluded that the soil environment affects the amount of leakage discharge. Results show that the particle diameter at 50% passing (D50), dry unit weight (γd) and hydraulic permeability coefficient (k) are more appropriate to represent the characteristics of soils. It was also concluded that there are no strong correlation between leakage and some soil parameters. The obtained relationships between different soil parameters and leakage discharge coefficients are also presented.

Research on Algorithm and Application of Shield Tunnel Distributed Optical Fiber Monitoring Data

Shield tunnels have different degrees of damage due to the differences in the surrounding soil properties, the disturbance of the soil during construction and the repeated loading of vehicles during operation, and there is a tendency to deteriorate with the increase of subway service time. The long-term and large-scale security status monitoring of shield tunnels is an important guarantee for the safety of subway operation. Two diagnostic algorithms based on strain monitoring data are proposed t in this paper, one is for the openness and dislocation of the segments, and the other is for the uneven settlement of the tunnel. The effectiveness of the two algorithms is verified by distributed optical fiber monitoring data of Beijing Metro Line 10. The calculation results are also compared with traditional monitoring methods. The proposition of these two algorithms provides a new idea for the analysis of distributed optical fiber shield tunnel monitoring data, which is beneficial to the promotion of distributed optical fiber monitoring technology.

Termite mound soil properties in West Bengal, India

Termites are ecosystem engineers, they play a major role in the biotransformation and modification of soil physicochemical and morphological properties. This study was conducted to evaluate the explored and compared physicochemical and morphological characteristics of soil between termite mounds and surrounding surface soil. Therefore, this study, especially emphasizes the impacts of the mound soil on the surrounding surface soil properties and also to find out the difference between the mound soil properties and surrounding surface soil properties at different soil depth, and characteristic of termite mounds. This study unveils that mound soil properties are directly proportional to the surrounding surface soil properties except for porosity and dispersion ratio. But mound soil properties are not significantly affecting all surface soil properties. The termites have a significant role to change soil physicochemical and morphological properties and there is a significant difference in soil physicochemical properties between mound and surrounding surface soil. However, relatively greater bulk density, clay content, soil pH, organic carbon, nitrogen, exchangeable calcium, exchangeable magnesium, exchangeable sodium, total exchangeable base cations and cation exchange capacity in mound soil than surrounding surface soil. But the relatively lesser value of porosity, dispersion ratio, exchangeable potassium, phosphorus, exchangeable acidity, and C: N ratio is found in mound soil than surrounding surface soil. Conical shaped mounds have greater nutrient concentration than surrounding surface soil. It also highlighted that most of the termite mound consists of trees and bushes containing 8–21 hole or chamber. The termite mounds have granular structure and particle shape are rounded to subrounded, which make them different from surrounding areas. This study suggests and statistically prove that termites have a significant effect on soil properties, they produce physicochemically more quality soil and have an influence on surrounding soil properties.

Application of Developed New Artificial Intelligence Approaches in Civil Engineering for Ultimate Pile Bearing Capacity Prediction in Soil Based on Experimental Datasets

In this study, a neural-fuzzy (NF) system is combined with group method of data handling (GMDH) in order to estimate the axial bearing capacity of driven piles. To reach optimum design of this conjunction (NF-GMDH) network, the metaheuristic techniques including particle swarm optimization (PSO) and gravitational search algorithm (GSA) were utilized. The datasets used for estimating pile bearing capacity were collected from the literature review. The parameters influencing the modeling and pile capacity analysis were taken into account as Flap number, surrounding soil properties, the pile geometric characteristics, and internal friction angles of the pile–soil interface. The efficiency of hybrid NF-GMDH networks in train and test phases was examined. Applying the PSO algorithm to the hybrid NF-GMDH model structure improved the model performance and achieved a higher level of accuracy in predicting the ultimate pile bearing capacity (RMSE = 1375 and SI = 0.255) compared to NF-GMDH model developed by GSA (RMSE = 1740.7 and SI = 0.357). In addition, based on achieved results, the developed NF-GMDH networks showed relatively better performances in comparison with gene programming and linear regression model methods considered in this study.

A data-driven approach for pipe deformation prediction based on soil properties and weather conditions

The health condition of infrastructure including water transmission and distribution mains has a great impact on the quality of human life. The performance of these water infrastructure is affected by the surrounding soil environment as well as the weather or climate changes. To investigate the structural response of water mains to varying soil movements, field data were collected with a sensor monitoring system. This included pipe wall strain in-situ soil water content, soil pressure, and temperature. Combined with weather factors, an automatic variable selection method, i.e., recursive feature elimination, was first applied to identify critical predictors contributing to pipe deformation. Then, a super learning algorithm was employed to characterize the relationship between pipe deformation and environmental factors. Both base and super learners were built to predict three types of pipe deformation which verified the adaptability of two modeling methods to different predictive models. Predictive performance was evaluated through R-squared, root-mean-square error, and mean absolute error values. The performance metrics demonstrate the advantage of the super learning algorithm in comparison with the baseline methods, especially its capability to further incorporate extra base learners and predictors in a more complex setting. This study shows that the pipe structure behavior could be successfully inferred from surrounding soil properties and weather conditions.

The impact of snow and soil freezing for commonly used foundation types in a subarctic climate

Heat losses from a building foundation are affected by both the surrounding conditions and the surrounding soil properties. These include many factors that complicate the analysis of heat loss, such as thermal storage, snow and soil freezing. The effect of snow and soil freezing was studied with a 3D simulation model in a subarctic climate.The heat losses from the most commonly used foundation types in Sweden were studied. This paper shows that it is possible to achieve a good thermal estimation of the air temperatures in a crawl space, with an average difference of 0.4 °C compared with the validation data over a year. Snow and soil freezing reduce the annual heat losses through the different foundation types by 7–10% and the maximum heat loss rate by 13–25%. In order to describe the heat transfer correctly, snow must be included in the calculations, while soil freezing has only a minor impact. The 3D model implemented in this study shows a significant impact on the soil temperatures when these parameters are included.For a subarctic climate, the commonly used calculation methods based on the European standard ISO 13370 are not thorough enough to calculate the heat transfer through a foundation accurately.

Effect of stone column installation on soft clay behavior

Installing a system of stone columns is a common ground improvement technique used in soft clay. The wished-in-place concept is usually applied to predict the load-settlement behavior of the treated ground. In this approach, the effect of the installation process on the properties of the surrounding soil is neglected. High radial displacements of the soil particles associated with the installation process of the stone columns, to achieve their target diameter, significantly alter the surrounding soil properties and affect the overall performance of the improved soil. This work aims to numerically study the influence of the stone column construction process on the improvement of soft ground by utilizing the finite element method. Different radial excitations have been considered in the analyses to mimic the construction procedure. Aspects of the two- and three-dimensional numerical analyses are combined in this study to overcome the local numerical instabilities.

Minimizing the impacts of contaminant intrusion in small water distribution networks through booster chlorination optimization

Contaminant intrusion in a water distribution network (DN) has three basic pre-conditions: source of contaminant (e.g., leaky sewer), a pathway (e.g., water main leaks), and a driving force (e.g., negative pressure). The impact of intrusion can be catastrophic if residual disinfectant (chlorine) is not present. To avoid microbiological water quality failure, higher levels of secondary chlorination doses can be a possible solution, but they can produce disinfectant by-products which lead to taste and odour complaints. This study presents a methodology to identify potential intrusion points in a DN and optimize booster chlorination based on trade-offs among microbiological risk, chemical risk and life-cycle cost for booster chlorination. A point-scoring scheme was developed to identify the potential intrusion points within a DN. It utilized factors such as pollutant source (e.g., sewer characteristics), pollution pathway (water main diameter, length, age, and surrounding soil properties, etc.), consequence of contamination (e.g., population, and land use), and operational factors (e.g., water pressure) integrated through a geographical information system using advanced ArcMap 10 operations. The contaminant intrusion was modelled for E. Coli O156: H7 (a microbiological indicator) using the EPANET-MSX programmer’s toolkit. The quantitative microbial risk assessment and chemical (human health) risk assessment frameworks were adapted to estimate risk potentials. Booster chlorination locations and dosages were selected using a multi-objective genetic algorithm. The methodology was illustrated through a case study on a portion of a municipal DN.

Shear Strength Design of a Mechanized Tunneling Grout Mix: Case Study of the Tehran Subway Line 6 Project

Ground subsidence caused by tunnel boring machines (TBMs), which is controlled by grout injection in the tail void, is one of the most adverse effects of excavation and tunnel construction processes. This article proposes a new method for designing the grout mix based on its shear rather than compressive strength, enabling a reduction in the amount of cement consumed. Moreover, the settlement caused by TBMs in line 6 of the Tehran subway is measured using a point network system. Since the ground subsidence induced by mechanized tunneling is predominantly caused by the tail skin settlement, the low amount of final ground settlement indicates that the grout mix with low cement content provides proper behavior to control the change of volume between excavated and external diameter of the precast lining. Moreover, a comparison of the grout and surrounding soil properties reveals that the injected grout should have a shear strength in the range of that of the excavated soil. This approach leads to lower cement consumption compared to a conventional design, which is based on compressive strength. In addition, less cement content causes less shrinkage and creep cracks which both improve waterproofing functionality. The measured settlement and segment damages (steps or lips in the tunnel) show that the face pressure, grout injection, and its mixture are applied in a safe manner.

Rate of Consolidation of Stone Column–Improved Ground Considering Variable Permeability and Compressibility in Smear Zone

AbstractUse of stone columns in soft soil reduces the excessive settlement and improves the bearing capacity with the additional advantage of providing a drainage path, which accelerates the rate of consolidation of the soil. Because of stone column installation in soft soil, surrounding soil properties are altered in such a manner that permeability and compressibility of the soil in the smear zone reduces and increases toward the drain, respectively. In the present paper, the effect of variable permeability and shear strength or compressibility in the smear zone due to stone column installation on the rate of consolidation of the stone column–improved ground was studied. The equal strain approach was considered in the analysis. The following three possible variation patterns of horizontal permeability and volume compressibility within the disturbed zone were considered: (1) reduced constant permeability with reduced constant compressibility, (2) linear variation of permeability with linear variation of c...

Assessment the influence of ground stratification, tunnel and surface buildings specifications on shield tunnel lining loads (by FEM)

Urban development and rapid extension of cities have been accompanied by a considerable growth in mechanized shield tunnelling. Commonly precast concrete segments are used as tunnel lining which comprises relatively considerable part of tunnelling cost. The optimum design of lining needs to an accurate evaluation of loads acting on the lining.In this paper, the effects of ground stratification, surface buildings specifications and tunnel depth on lining loads were studied. For this purpose a 3D finite element model was used employing the ABAQUS software (Ver. 6.11). The geometry of tunnel, lining segments, injection grout and the surrounding soil properties were adopted from the under construction Tabriz urban railway line 2 project.The results show that the studied parameters have considerable effects on lining loads. For mentioned case study, surface buildings with 5 and more story have a considerable effect on lining loads, especially for shallow tunnels. The geometry of surface buildings influences the internal forces of the tunnel lining and increase of buildings width and length increases the lining loads. The building width is the most important parameter and with increase of that the influence of other parameters increases. Also by comparison of obtained results in this study with results of 2D analysis, reliability of 2D models was investigated. The comparisons show that 3D analysis is superior to 2D analysis, particularly in the cases of surface buildings presence. The difference between results increases with decrease of building length and increase of tunnel depth and building weight.

Comparative Analysis of Termiteria and Surrounding Soil Properties in the University of Agriculture, Makurdi, Nigeria

Variations in the properties of termitaria and their surrounding soil properties within the University of Agriculture Makurdi were investigated using routine soil analysis protocol. Parameters such as texture, pH, cationic exchange capacity (CEC), organic carbon (OC), available phosphorus (AP) and total nitrogen (TN) were determined alongside with the elemental (Cu, Mn, Zn, Fe, Cd, Pb, Na, K, Ca, Mg and Al) analysis. There were clear disparity in the texture (clay content), pH level, AP and TN within the mound and in the environs. Similarly, elemental analysis shows significant variability of the elements among sites ranging from 0.02-196 mg/kg and 0.01-172 mg/kg for the termitaria and surrounding soils, respectively. The predominant analyte is Al, which is the most abundant element in the earth crust. The results show that trace elements such as Mn and Fe, are significantly higher in the termite mounds compared to the surrounding soils. Therefore, we recommended that farming should be carried out very close to the termitaria soils since these elements were essential to plants and animals. Keywords: AAS, Heavy metals, Makurdi, Soils, Termites

Plate Load Tests of Composite Foundation Reinforced by Concrete-Cored DCM Pile

The concrete-cored deep cement mixing (DCM) pile is a new kind of composite pile created by inserting precast core pile into the DCM column socket and has only been used in a few projects to date. The bearing mechanism of concrete-cored DCM pile composite foundation has not been investigated systematically. In this paper, plate load tests (PLT) on single pile composite foundation were conducted in Nanjing–Changzhou expressway, Xinhua district in Jiangyin city and Nanjing surrounding (NS) expressway. Following the results of the PLT, a comparison of ultimate bearing capacity between composite foundation reinforced by concrete-cored DCM pile and DCM column was made. During the PLT process, the vertical stress of surrounding soil and DCM column socket was measured using pressure cells. The vertical stress of precast core pile was obtained using steel stress gauge welded onto the reinforcement. Based on the vertical stress of surrounding soil, DCM column socket and precast core pile, the skin friction and load sharing ratio were obtained. The variation in surrounding soil properties depending on the installation of concrete-cored DCM pile was also analyzed using the results from cone penetration tests (CPT) taken in NS expressway. With the analysis of results for stress tests and CPT, the bearing mechanisms of composite foundation reinforced by concrete-cored DCM pile are obtained.

Two-dimensional pipe leakage through a line crack in water distribution systems

In water distribution systems, water leakage from cracked water pipes is a major concern for water providers. Generally, the relationship between the leakage rate and the water pressure can be modeled by a power function developed from the orifice equation. This paper presents an approximate solution for the computation of the steady-state leakage rate through a longitudinal line crack of a water distribution pipe considering the surrounding soil properties. The derived solution agrees well with results of numerical simulations. Compared with the traditional models, the new solution allows assessment of all the parameters that related with leakage including the pressure head inside the pipe, hydraulic conductivity, crack size and its position, and pipe size and its depth.

Prediction of the shaft resistance of nondisplacement piles in sand

SUMMARYUsing pile segment analysis, the mobilized shaft resistance of axially loaded nondisplacement piles in sand is investigated here. It is accepted that the shaft capacity of piles constructed in granular soils is highly influenced by the mechanical behavior of soil–structure interfaces forming adjacent the piles skin. Adopting the thin interface layer as a load transfer mechanism, a simple but accurate critical state compatible interface constitutive model is introduced. After evaluation, the interface model in conjunction with the pile segment analysis is applied for the prediction of the shaft resistance mobilized in nondisplacement piles. The proposed approach takes into account the influences of pile diameter and surface roughness together with the effects of the surrounding soil density and stiffness on the mobilized shaft resistance. The performance of the proposed method is verified by comparing its predictions with the experimental data of various model piles covering wide ranges of length, diameter, roughness, and surrounding soil properties. Copyright © 2012 John Wiley & Sons, Ltd.

Sensitivity study on depressurized LOFC accidents with failure of RCCS in a modular gas-cooled reactor

A modular gas-cooled reactor design with a thermal output of 600 MWt and a core exit temperature of 950 °C has been designed by the Korea Atomic Energy Research Institute based on the GT-MHR reactor concept which adopts a prismatic core. A sensitivity study on the transient plant behavior during a postulated depressurized LOFC accident concurrent with the failure of the RCCS was performed. In the transient analysis, the GAMMA+ code which can handle multi-dimensional, multicomponent problems was used. The RCCS is a passive system which is very reliable and supplies a significant heat removal mechanism during abnormal conditions in a GCR. To investigate the safety characteristics of a GCR under the one of the worst accidental scenarios, a simultaneous failure of the RCCS with a depressurized LOFC was assumed. The thermal behavior of the reactor system was analyzed in various conditions. It is found that the maximum temperature of the reactor fuel compact could exceed 1600 °C at about 50 h at the condition of a depressurized LOFC with a failure of the RCCS. A problem with the structural integrity of the reactor pressure vessel could also be a critical factor. The insulation of a reactor cavity wall serves as a dominant obstacle against a heat transfer from the reactor vessel to the surrounding ground when the RCCS fails to operate. Without insulation material on the reactor cavity wall, the gradients of the increasing rate of the maximum temperature diminish and the peak values decrease. The maximum temperatures of the fuel compact and the reactor vessel are less sensitive to the concrete and surrounding soil properties, those are the thermal conductivity and volumetric heat capacity, when the insulation material is used. The uncertainties in the properties of the concrete and the surrounding soil become significant without an insulation material in the cavity. To improve the safety of a modular GCR, more effective and feasible heat removal mechanism need to be devised based on the comprehensions on the heat transfer characteristics.

Fuzzy Expert System to Assess Corrosion of Cast/Ductile Iron Pipes from Backfill Properties

: Several factors may contribute to the structural failure of cast and ductile iron water mains, the most important of which is considered to be corrosion. The ANSI/AWWA C105/A21.5-99 10-point scoring (10-P) method is commonly used to predict the corrosivity potential of a given soil sample using certain soil properties. The 10-P and other scoring methods use binary logic to classify the soil as either corrosive or noncorrosive. Fuzzy logic extends binary logic in this context as it recognizes the real world phenomena using a certain degree of membership between 0 and 1. This article presents a fuzzy logic expert system capable of predicting the deterioration of cast and ductile iron water mains based on surrounding soil properties. The proposed model consists of two modules: a knowledge base and an inference mechanism. The knowledge base provides information for better decision making and is developed in a two-tier fuzzy modeling process. First in direct approach, the expert knowledge generates a subjective model to describe the characteristics of the system using fuzzy linguistic variables. Later in system identification, the field data are used to develop an objective model, which is eventually used in conjunction with the subjective model to provide a more reliable knowledge base for the expert system. The inference mechanism uses fuzzy approximate reasoning methods to process the encoded information of the knowledge base.

The impact of ant bioturbation and foraging activities on surrounding soil properties

Nest building and foraging activities are two of the many ways that ants impact on the surrounding soil environment within and beyond the mound. These activities have both long- and short-term effects on the soil part of the ecosystem through structural alterations, nutrient accumulation and release, with possible enhancement of soil quality. This study illustrates the impact of ant foraging activities on the soil and the pattern of arrangement existing in soil properties in the mound soil environment. Eight active mounds of Iridomyrmex greensladei , greater than 50 cm in diameter, were randomly selected from four blocks in a vegetation remnant adjacent to the main Wee Waa highway, Narrabri, New South Wales. The soil volume, soil mass and slope for each mound was characterised. Soil samples were collected in the plots at 0–10 cm depth from the top of the mound, the mound perimeter, 5 m radius from the mound perimeter, the foraging tracks, and from other locations unaffected by ant activity. The soil samples were analysed for physical and chemical properties. The extent of pore distribution as cavities and galleries, was evaluated by taking photographs of a cross section of an ant mound after pouring in water miscible paint (1:8 paint to water suspension) into an open cut on the top of the mound. The paint moved through the pores, to a depth of about 150–200 cm from the surface through vertical and lateral galleries. In comparison to the surrounding soil, ant-impacted soils were lower in clay, higher in sand and silt, and lower in exchangeable Ca, Mg, K and Na. The top of the mound was higher in NO 3 , P and more compacted than soils not modified by ant mounds. Ant-impacted soils had low dispersion indices compared with unmodified soil. Ant bioturbation activities increased soil porosity in the mounds extending to about 200 cm down the soil profile. Ant bioturbation and foraging activities were found to affect soil properties beyond the perimeter of the mound and into the surrounding ecosystem.