Determination of the Hydrodynamic Parameters of Two Types of Soil in the Senegal River Delta. Simulation of Hydro-saline Transfers: Application to the Wind Deflation Phenomenon

In the Senegal River delta, the presence of a shallow salt water table associated with a strong evaporative demand sometimes leads to an upwelling of salts that crystallize on the surface. This phenomenon can be observed in the vicinity of the Diawling Basin, where a powdery structure sensitive to wind deflation and a massive structure with a fractionation into platelets that cannot be transported by the wind are noted. To understand the hydrodynamic characteristics of these soils, we used numerical simulation of water and solute transfers. The hydrodynamic parameters were determined in the laboratory using Wind's method on undisturbed samples. The experimental retention h() and hydraulic conductivity K(h) curves were fitted using the Van Genuchten model. The simulations show that the soil with a powdery structure has hydrodynamic characteristics that favour the ascent of salts from the water table to the surface. For the soil with a massive structure, the hydrodynamic conditions impose a deposition of salts in the subsurface.

Strength and Compressibility of Ammonia-Soda Residue from the Solvay Sodium Plant

This work presents the discussion of the results for an experimental study conducted to characterise the mechanical behaviour of ammonia-soda residue (ASR). The calcareous sludge is an alkaline waste formed during the production of soda ash and deposited at the area of the former Solvay Sodium Plant factory in Krakow, Poland. Isotropically consolidation drained (CID) triaxial tests and constant rate of strain (CRS) consolidation tests include the full saturation with water, completion of the consolidation, and the loading/strain rate choice. For this purpose, ASR undisturbed samples were collected from the ground and submitted to laboratory experiments. These samples show a distinct difference in the initial bulk density, the initial level of compaction, initial void ratio, and the natural water content. The CD triaxial tests were conducted under three different levels of confining pressure; in turn, CRS tests were run with two appropriate input strain rates. According to the physical state of ASR and the depth of sampling, two different evolutions of the critical state in the stress–strain space were observed. In the light of the assessed stress–strain–strength behaviour, key design engineering parameters of ASR were calculated.

Compressibility and consolidation properties of Santos soft clay near Barnabé Island

A geotechnical study based on characterization tests and seventy incremental loading onedimensional consolidation tests was carried out on high-quality undisturbed samples taken from Santos Harbor Channel subsoil near to Barnabé Island, where a pilot embankment was built. The characterization profiles revealed a stratigraphy following the pattern described by Massad (2009), with a 9 m-thick fluvial-lagoon-bay sediments (SFL) clay layer. The consolidation tests were performed following two loading criteria. In criterion A (series one tests), a new loading was applied whenever the strain rate (ε) reached 10-6 s-1, the highest integer power of 10 after the “end of primary” consolidation for double drained 2 cm-thick specimens. In criterion B (series two tests), the standard procedure of 24 hour-long stages was adopted. Criterion A reduced the total duration of the consolidation tests from ten to about three days. The preconsolidation (yield) stress (σ’p) and the compressibility parameters Cc and Cr obtained from “e versus σ’v (log)” compression curves of all tests are provided. Series two tests showed that the 24-hour “e versus σ’v (log)” compression curves are translated to the left of the ε = 10-6 s-1 “e versus σ’v (log)” compression curves, keeping Cr and Cc average values unchanged, but decreasing σ’p by about 8%. The SFL clay Cc/(1+e0) values obtained herein are higher than those presented by Massad (2009) due to the higher-quality samples tested in this study. It is shown that it is feasible to carry out a high-quality laboratory test program for design purposes following current standards.

Correlation between Compaction Characteristics with undrained Shear Strength of Soils found in Burayu Town

The shear strength of the soil is an important factor to know the internal resistance of soil against external loads causing shearing forces. Shear strength parameters are mandatory for the analysis of load bearing capacity of the soil, the stability of Geotechnical structures and in analysing stress and strain characteristics of soils. The undrained shear strength is one type of shear strength parameter. This parameter is conducted by undisturbed samples. But due to handling, transportation, release of overburden pressure and poor laboratory conditions, it is difficult to obtain accurate undisturbed samples. So, prediction of undrained shear strength parameters (cu) for cohesive soil with the help of compaction characteristics provides a good alternative to minimize this problem. Therefore, this study was conducted to develop the correlation between undrained shear strength values with soil compaction characteristics specifically located in Burayu town. The study was carried out using thirty samples collected from the town. By using the test result regression based statistical analysis was carried out to develop the intended correlation. The parameters considered for this study are Atterberg's limits, Grain size analysis, Specific gravity, Compaction tests and unconfined compression test. The test procedures were based on AASHTO and ASTM laboratory test standards. These parameters are used to establish equations of correlations between undrained shear strength values with soil compaction. The soil type found in Burayu town was highly plastic red clay soil. Based on both single and multiple linear regression analysis relatively good correlation is obtained by combining undrained shear strength (qu ) with maximum dry density and optimum moisture content of red clay soil. From the correlation analysis the equations developed are qu = - 3105 + 1625 MDD + 40.9 OMC with coefficient of determination of R2 =0.828 for multiple linear regression and qu= - 1473 + 57.8 OMC and qu= - 4861 + 3910 MDD with coefficient of determination of R2=0.787 and R2 =0.601 for single linear regression respectively. Generally, the intended correlation obtained from the study area fulfil the basic requirement of regression.

Evaluation of Collapse Sensitivity of Loess Soils and Its Effect on the Distribution Pattern of Pseudokarst Sinkholes at the Regional Scale (Case Study: Golestan Province, Northeastern Iran)

The spread of loess soils in Golestan Province in northeastern Iran has caused considerable environmental issues. To evaluate the effect of loess collapse on the spatial distribution of pseudokarst sinkholes in this province, we have prepared undisturbed samples from 31 locations and characterized their physical and mechanical properties. Moreover, the collapse sensitivity in different parts of the study area has been determined by odometer tests under different pressures and calculation of three parameters, namely, the collapse coefficient (Ic), the time required for 90% settlement due to soil collapse (T90%), and initial collapse stress. Additionally, by conducting field surveying, using aerial photographs, satellite images, and drone flight, the coordinates of sinkholes were identified, and a map of their geographical distribution was prepared. The overlap of the sinkholes distribution map and the coefficient of collapse changes map showed that although the amount of Ic of sandy loess soils (Zone III) is higher than that of silty loess soils (Zone II), the extent of destructive phenomena such as sinkholes is much greater in Zone II than in Zone III. The overlap of the map of sinkholes distribution with the map of changes in collapse sensitivity (Is) of loess soils showed that the density of sinkholes in Zone II (which has higher collapse sensitivity) is higher than Zone III. In Zone II, due to severe collapse sensitivity, the highest concentration of sinkholes is observed in a unit area, more than 0.18 per square kilometer. With a relatively severe to severe collapse sensitivity in Zone III, this concentration is 0.021 per square kilometer. In Zone I (clayey loess), with slight-moderate collapse sensitivity, this destructive phenomenon is observed in the form of side instability since the study area is located in highlands. Furthermore, in this area, the sinkholes (0.004 per square kilometer) have the least concentration.

Comparative Study of Soil Index Properties of Gudu Sokoto State And Oworoshoki Area Lagos State, Nigeria.

The comparative study of the soils sample collected from Gudu and Oworoshoki area, Sokoto state and Lagos State was carried out to compare the index properties of soil at shallow soil deposit. The Global Positioning System (GPS) was used to locate the coordinates of the site. Shallow soil samples (disturbed and undisturbed) at different depths (1m, 2m and 3m) were collected from both study areas (Gudu and Oworoshoki). The disturbed samples were collected using hand trowel, digger, hoe and polythene bags while the undisturbed samples were collected using short pipes (samplers) by stroking each pipe into the ground completely with a hammer at each depth. Disturbed and undisturbed soils collected at different shallow depths (1m, 2m and 3m) were taken to the laboratory for natural moisture content, specific gravity, sieve analysis, Atterberg limits and unit weight test. Empirical equations were used for analyzing the soil samples and AASTHO System of classification was used for classifying the soil samples. The results of the test on Gudu soil samples has shown that the soil sample collected at depth 1.0m and 2.0m are nonplastic materials and were classified according to AASHTO standard as A-3 and sample at depth 3.0m as A-4 which is silty soil while Oworoshoki soil samples has shown that Soils from depth 1.0m, 2.0m and 3.0m are nonplastic (NP) because the Plastic Index (PI = 0) is zero and the soil samples are classified as A – 3 according to AASHTO standard.

Geotechnical Investigations of an Earth-Filled Site for Construction of a Building

There is a growing need of construction around the globe. This need tends to provide newer opportunities for construction of buildings over reclaimed lands or earth filled areas. Mostly, the earth is filled with soils as it is an easily available material. Soil is a complex materials, and its properties can vary due to several reasons. If not understood properly, it can damage undisturbed samples collected from earth-filled soils. The basic properties of soils, the stress-strain behavior and strength parameters are presented and discussed. Results show that soil exhibits strain hardening and normally consolidated behavior in direct shear and oedometer test respectively. It is observed that the compression index values are in the range of 0.157 to 0.182 which indicates that the material is silty soils with low plasticity. The allowable bearing capacity in our study was 305 kPa and allowable load on footing was 987 kN. The strength parameters, i.e., friction angle and cohesion are 37 degree and 2 kPa respectively.

Shear modulus and damping ratio of sensitive Eastern Canada clays

The shear modulus and equivalent viscous damping ratio of three sensitive clays from the sediments of the Champlain Sea were investigated using a combined triaxial simple shear apparatus. The tests were conducted on undisturbed samples and were carried out on a wide range of shear strain from about 0.001% to 1%. The values of the small strain shear modulus of the tested clays were further confirmed through a series of piezoelectric ring actuator and MASW tests. Although the shear modulus and damping ratio of the sensitive eastern Canada clays follow some classic literature models, the results show that the examined clays exhibited more linear behaviour. Such behaviour may be attributed to their highly structured nature compared to other clays. The compilation of available data on the shear modulus and damping ratio of several sensitive eastern Canada clays confirmed this trend and showed that some literature models might not be representative.

The influence of channel network silting up at Žitný Ostrov to range of interaction between surface and groundwater

The movement of water resources, especially the possibilities of their regulation by interaction between surface and groundwaters are the subject matter of attention particularly during the occurrence of extreme hydrologic situation. This work presents the overview of knowledge and results which were achieved at IH SAS in this question. It can show the ways how to optimize the adjudicated processes which emerge during the requirement of emergency intervention. The solution of this task was located at the Žitný Ostrov area because this territory with their existence of channel network is suitable for studying the surface and groundwater interaction. The channel network at Žitný Ostrov was built up for drainage and also to safeguard irrigation water. The water level in the whole channel network system has an effect on groundwater level on the Žitný Ostrov and vice versa. It was been necessary to judge the impact of the channel network silting up by bed silts on the interaction between channel network and groundwater on the Žitný Ostrov. The aim was to evaluate the changes of bed silt state of Žitný Ostrov channel network and consecutively their influence on interaction processes between groundwater and surface water along the channels in the period from 1993 to present. The measurements of bed silt thickness in Žitný ostrov channel network had been started from1993, later they continued at selected profiles of three main channels – channel Gabčíkovo-Topoľníky, Chotárny channel and Komárňanský channel (for checking of the silting up variability). From 2008 the detailed field measurements of cross-section profiles aggradations along these selected three channels have been started. The objective of detailed field measurements was the determination of the silt permeability which is expressed by parameter of saturated hydraulic conductivity. This parameter was determined by two ways – as the saturated hydraulic conductivity obtained from disturbed samples of silt Kp and as the saturated hydraulic conductivity obtained from undisturbed samples of silt Kn. In the first case the granularity of silts was determined as a first step and then was computed their Kp from the empirical formulas according Bayer-Schweiger and Spacek. From undisturbed samples of silts which were extracted along the channels from top, middle and bottom layer of silts, were determined the values Kn by the laboratory falling head method. The valid values Kp on channel Gabčíkovo-Topoľníky ranged from 4,33 10-7 to 4,46.10-5 m s-1, on Chotárny channel from 5.98 10-5 to 2.14 10-6 m s-1 and on Komárňanský channel fluctuated from 1.93 10-6 – 6.09 10-5 m s-1. The valid values Kn on on channel Gabčíkovo-Topoľníky ranged from 5.21 10-8 – 4.18 10-3 m s-1 , on Chotárny channel ranged from 8.54 10-8 – 2.70 10-4 m s-1 and on Komárňanský channel fluctuated from 4.72 10-7 – 1.26 10-5 m s-1. The remarkable results were noticed by comparison of values of saturated hydraulic conductivity from disturbed and undisturbed samples Kp and Kn. On Chotárny channel the values of silt saturated hydraulic conductivity from undisturbed samples Kn approximately hundredfold decreased (from 10-6 to 10-8 m s-1). On Komárňanský channel the comparison of values Kp and Kn shown that the values Kn from undisturbed samples approximately tenfold descended against Kp. Simultaneously, the bed silts‘ impact on the groundwater recharge (saturated hydraulic conductivity of silt) was also examined. Determination of the total recharge amount was done by numerical simulation (model SKOKY) and by the so-called method of interaction formulas. These two approaches were applied at the Žitný Ostrov channel network. There were field measurements performed in monitored three main channels and adjacent to obtain correct input data. These characteristics were used for simulation and computation of total recharge along the channels. The total recharge amount was calculated for four alternatives of the surface water levels in the channel and the surroundings groundwater respectively. We chose four simplified variants with the same geological conditions in surroundings area of channels, only water levels of groundwater and in channels were modified. The results of the simulations seem to show greater impact of the silt in the case of outflow from the channels to the surroundings than the inflow into the channel from the surroundings.