Soil disturbance evaluation of soft clay based on stress-normalized smallstrain stiffness

Soil disturbance includes the change of stress state and the damage of soil structure.The field testing indices reflect the combined effect of both changes and it is difficult to identify the soil structure disturbance directly from these indices.In the present study,the small-strain shear modulus is used to characterize soil structure disturbance by normalizing the effective stress and void ratio based on Hardin equation.The procedure for evaluating soil sampling disturbance in the field and the further disturbance during the subsequent consolidation process in laboratory test is proposed,and then validated by a case study of soft clay ground.Downhole seismic testing in the field,portable piezoelectric bender elements for the drilled sample and bender elements in triaxial apparatus for the consolidated sample were used to monitor the shear wave velocity of the soil from intact to disturbed and even remolded states.It is found that soil sampling disturbance degree by conventional thin-wall sampler is about 30%according to the proposed procedure,which is slightly higher than that from the modified volume compression method proposed by Hong and Onitsuka(1998).And the additional soil disturbance induced by consolidation in laboratory could reach about 50%when the consolidation pressure is far beyond the structural yield stress,and it follows the plastic volumetric strain quite well.

Drilling Power Consumption and Soil Conveying Volume Performances of Lunar Sampling Auger

The sampling auger used in lunar sampling and return mission is to transmit power and convey soil, and its performance is the key factor of the whole mission. However, there is currently a lack of the optimization research on soil conveying volume and power consumption models in auger structure design. To provide the drilled object, the simulation lunar soil, whose physical and mechanical property is the same as the real soil, is made by reducing soil void ratio. The models are formulated to analyze the influence of auger structure parameters on power consumption and soil conveying volume. To obtain the optimized structure parameters of auger, the multi-objective optimization functions of the maximum soil conveying volume and minimum power consumption are developed. To verify the correctness of the models, the performances of different augers drilling simulation soil are tested. The test results demonstrate that the power consumption of optimized auger is the lowest both in theory and test, and the experimental results of soil conveying volume are in agreement with theoretical analysis. Consequently, a new method for designing a lunar sampling auger is proposed which includes the models of soil conveying volume and transportation power consumption, the optimization of structure parameters and the comparison tests. This method provides a reference for sampling auger designing of the Chinese Lunar Sample Mission.

Infiltration characteristics of non-aqueous phase liquids in undisturbed loessal soil cores

The widespread contamination of soils and aquifers by non-aqueous phase liquids （NAPL）, such as crude oil, poses serious environmental and health hazards globally. Understanding the infiltration characteristics of NAPL in soil is crucial in mitigating or remediating soil contamination. The infiltration characteristics of crude and diesel oils into undisturbed loessal soil cores, collected in polymethyl methacrylate cylindrical columns, were investigated under a constant fluid head （3 era） of either crude oil or diesel oil. The infiltration rate of both crude and diesel oils decreased exponentially as wetting depth increased with time. Soil core size and bulk density both had significant effects on NAPL infiltration through the undisturbed soil cores; a smaller core size or a greater bulk density could reduce oil penetration to depth. Compacting soil in areas susceptible to oil spills may be an effective stratage to reduce contamination. The infiltration of NAPL into soil cores was spatially anisotropic and heterogeneous, thus recording the data at four points on the soil core is a good stratage to improve the accuracy of experimental results. Our results revealed that crude and diesel oils, rather than their components, have a practical value for remediation of contaminated loessal soils.

N_2O emissions from a cultivated Andisol after application of nitrogen fertilizers with or without nitrification inhibitor under soil moisture regime

The aim of this work was to examine the emission of N 2O from soils following addition of nitrogen fertilizer with a nitrification inhibitor(+inh) or without the nitrification inhibitor(-inh) at different soil water regime. Higher soil moisture contents increased the total N 2O emissions in all treatments with total emissions being 7 times larger for the CK and >20 times larger for the fertilizer treatments at 85% WFPS(soil water filled pore space) than at 40% WFPS. The rates of N 2O emissions at 40% WFPS under all treatments were small. The maximum emission rate at 55% WFPS without the nitrification inhibitor(-inh) occurred later (day 11) than those of 70% WFPS (-inh) samples (day 8). The inhibition period was 4—22 d for 55% WFPS and 1—15 d for 70% WFPS comparing the rates of N 2O emissions treated (+inh) with (-inh). The maximum emission rates at 85% WFPS were higher than those at the other levels of soil water content for all treatments. The samples(+inh) released less N 2O than (-inh) samples at the early stage. Nevertheless, N 2O emissions from (+inh) samples lasted longer than in the (-inh) treatment. Changes in mineral N at 55%, 70% and 85% WFPS followed the same pattern. NH + 4-N concentrations decreased while NO - 3-N concentrations increased from the beginning of incubation. NH + 4-N concentrations from 40% WFPS treatment declined more slowly than those of the other three levels of soil water content. Nitrification was faster in the (-inh) samples with 100% NH + 4-N nitrified after 22 d(50% WFPS) and 15 d(70% and 85% WFPS). N 2O emissions increased with soil water content. Adding N-fertilizer increased emissions of N 2O. The application of the nitrification inhibitor significantly reduced total N 2O emissions from 30.5%(at 85%WFPS) to 43.6%(at 55% WFPS).

Cobalt in alluvial Egyptian soils as affected by industrial activities

Twenty five surface (0—20 cm) soil samples were collected from different locations in Egypt representing non polluted, moderately and highly polluted soils. The aim of this study was to evaluate total Co content in alluvial soils of Delta in Egypt using the delayed neturen activation analysis technique (DNAA). The two prominent gamma ray lines at 1173 2 and 1332 5 keV was efficiently used for 60 Co determination. Co content in non polluted soil samples ranged between 13 12 to 23 20 ppm Co with an average of 18 16±4.38 ppm. Cobalt content in moderately polluted soils ranged between 26 5 to 30 00 ppm with an average of 28 3±1.3 ppm. The highest Co levels (ranged from 36 to 64 69 ppm with an average of 51 9±9.5); were observed in soil samples collected from, either highly polluted agricultural soils due to prolonged irrigation with industrial wastewater or surface soil samples from industrial sites.

Discussion on Atmospheric Pollutant Source Seeking Model with Surface Soil Sample

Through the analysis on the migratory diffusion process of atmospheric pollutants,we proposed to seek atmospheric pollutant source with surface soil sample of data.Based on Gaussian plume model and deposition model,atmospheric pollutants distribution model was deduced,with which a schema matching source seeking model was established.The model was used to seek the pollutant source by using the arsenic data in the surface soil sample of a city.

Screening and Characterization of Antibiotic Producing Organisms from Waste Dump Soil Sample

This study was designed to screen and characterize antibiotic producing bacteria and fungi from soil samples from a waste dump site in Enugu. The molecular characterization of the isolates was performed by using Zymo Research Quick-DNA fungi/bacteria miniprep kit. The bacteria isolates were Providencia stuartii, Providencia alcalifaciens. Bacillus sp., Streptococcus sp., Micrococcus sp., and Staphylococcus sp while Aspergillus fumigatus and Aspergillus niger were fungal isolates. The efficacy of the Crude Extract (CE) of the antibiotics produced was tested against species of Staphylococcus aureus and Escherichia coli. The CE of antibiotics when compared with a conventional antibiotic (Ciprofloxacin) showed lower antimicrobial activity. The minimum inhibitory concentration of the crude extracts ranged between 12.5% and 25% concentrations while the minimum bactericidal concentration ranged from 25% and 50% concentrations. The findings suggest that these organisms have the potential to produce antibiotics and could be harnessed by pharmaceutical industries for the production of newer antibiotics.

Effects of Soil-Cement Stabilization on the Index Properties of Subgrades of Three Selected Roads in the Niger Delta Region of Nigeria

In this study, the impact of soil-cement stabilization on the index properties of the subgrade of roads was investigated. Efforts were on the means of improving the bearing capacity of the subgrade of a flexible pavement structure. Three selected roads (Ogbia-Nembe, section of the East-West Road and section of Port Harcourt-Aba Road) in the Niger Delta Region of Nigeria were examined to determine the effect of sand-cement stabilization on the compaction index property of their undisturbed subgrade and the optimal ratio of soil-cement on the expansive soils at which the California Bearing Ratio (CBR) is optimized. Disturbed soil samples were collected from twenty trial pits on each of the three study roads using a hand ulger and tested for their respective compaction index properties. It was discovered that their California Bearing Ratio (CBR) was very low. Some of the collected specimen materials were stabilized with varying percentages of soil-cement contents ranging from 6% - 14% in order to ascertain its effects on the compaction index properties of the sample soils. Results of the various stabilization test procedures show that: Stabilization of the soil using Soil-Cement Stabilization affected the Compaction Index properties of the soil and further improved the California Bearing Ratio (CBR). On the Ogbia-Nembe Road;Soil-Cement stabilization improved the CBR and is optimized at a 10% sand-cement ratio with optimum moisture content ranging from 6.2% - 14%, maximum dry density ranges from 1700 - 1780 kg/m3, yielding an average CBR of 42.7% for soaked samples. On the section of East-West Road from Eleme Junction to Etteh Junction;Soil-Cement stabilization improved the CBR and is optimized at a 14% sand-cement ratio with optimum moisture content ranging from 6.2% - 14.2%, maximum dry density ranges from 1660 - 1800 kg/m3, yielding an average CBR of 43.9% for soaked samples. On the section of Port Harcourt-Aba Express Road from Eleme Junction to Osisioma Junction;Soil-Cement stabilization improved the CBR and is optimized at a 12% sand-cement ratio having an optimum moisture content ranging from 5.4% - 17.3%, maximum dry density ranges from 1610 - 1740 kg/m3, and an average California Bearing Ratio for soaked samples at 40%.

Development of a Drilling and Coring Test-bed for Lunar Subsurface Exploration and Preliminary Experiments

Drill sampling has been widely employed as an effective way to acquire deep samples in extraterrestrial exploration. A novel sampling method, namely, flexible-tube coring, was adopted for the Chang＇e mission to acquire drilling cores without damaging stratification information. Since the extraterrestrial environment is uncertain and different from the terrestrial environment, automated drill sampling missions are at risk of failure. The principles of drilling and coring for the lunar subsurface should be fully tested and verified on earth before launch. This paper proposes a test-bed for conducting the aforementioned experiments on earth. The test-bed comprises a rotary-percussive drilling mechanism, penetrating mechanism, drilling medium container, and signal acquisition and control system. For granular soil, coring experiments indicate that the sampling method has a high coring rate greater than 80%. For hard rock, drilling experiments indicate that the percussive frequency greatly affects the drilling efficiency. A multi-layered simulant composed of granular soil and hard rock is built to test the adaptability of drilling and coring. To tackle complex drilling media, an intelligent drilling strategy based on online recognition is proposed to improve the adaptability of the sampling drill. The primary features of this research are the proposal of a scheme for drilling and coring a test-bed for validation on earth and the execution of drilling experiments in complex media.

Assessment of Geologic Controls of Flooding in Parts of OBIO/AKPOR L.G.A., Rivers State, Nigeria

Flooding of Municipal areas is a frequent environmental occurrence in Rivers State that occurs when rainfall runoff meets land surfaces with low water absorbing capacity or when it overwhelms drainage channels.In order to assess the flood situation in the study area,an integrated method which involves field-measurement,geographic information system(GIS),laboratory analysis of soil samples and topographic studies were employed.Digital elevation model of the study area reveals that the flooded areas are situated in areas with elevations lower than its surrounding,thereby acting as a natural basin to retain flood waters after rainfall.Four holes were drilled to depth of 3 m to obtain soil samples at 1 m sampling interval,from which laboratory analysis was carried out to determine some geotechnical parameters such as soil’s particle size,specific gravity,bulk density,porosity,moisture content,permeability and hydraulic conductivity.Results of the analysis show that permeability,hydraulic conductivity and porosity diminishes with respect to depth.The soil in the flooded areas have high fines content(silt and clay),high bulk density which increase with depth and a specific gravity that is typical of organic rich soils that contain sand mixed with a considerable amount of fines.At Nkpolu,mean permeability rates of 0.003 cm/sec,0.009 cm/sec and 0.033 cm/sec were obtained at 1,2 and 3 m respectively.At Eneka,mean permeability rates of 0.011 cm/sec,0.018 cm/sec and 0.014 cm/sec were obtained at 1,2 and 3m respectively,while at Rukpokwu,mean Permeability rates of 0.021 cm/sec was obtained at 1 m,while 0.006 cm/sec was obtained at 2 and 3 m respectively.The mean hydraulic conductivity for the locations under study is of the order of 10-4 ft/day.This study has shown that the flooded areas are located in low lying urban areas which act as basins,therefore,the top soil is crusted with highly compacted soil horizons beneath.With high and frequent rainfall in the region which generates a lot of runoff,in addition to poor drainage system,flooding in the study area occurs frequently.Therefore,construction and maintenance of efficient drainage channels for an effective solution to urban pluvial flooding in the study area are thereby recommended.

Soil property mapping by combining spatial distance information into the Soil Land Inference Model(SoLIM)

The Soil Land Inference Model(SoLIM) was primarily proposed by Zhu et al.(Zhu A X, Band L, Vertessy R, Dutton B. 1997. Derivation of soil properties using a soil land inference model(SoLIM). Soil Sci Soc Am J. 61: 523–533.) and was based on the Third Law of Geography. Based on the assumption that the soil property value at a location of interest will be more similar to that of a given soil sample when the environmental condition at the location of interest is more similar to that at the location from which the sample was taken, SoLIM estimates the soil property value of the location of interest using the soil property values of known samples weighted by the similarity between those samples and the location of interest in terms of an attribute domain of environmental conditions. However, the current SoLIM method ignores information about the spatial distances between the location of interest and those of the sample. In this study, we proposed a new method of soil property mapping, So LIM-IDW, which incorporates spatial distance information into the SoLIM method by means of inverse distance weighting(IDW). The proposed method is based on the assumption that the soil property value at a location of interest will be more similar to that of a known sample both when the environmental conditions are more similar and when the distance between the location of interest and the sample location is shorter. Our evaluation experiments on A-horizon soil organic matter mapping in two study areas with independent evaluation samples showed that the proposed SoLIM-IDW method can obtain lower prediction errors than the original SoLIM method, multiple linear regression, geographically weighted regression, and regression-kriging with the same modeling points. Future work mainly includes the determination of optimal power parameter values and the appropriate setting of the parameter under different application contexts.

Complex Effective Relative Permittivity of Soil Samples from the Taunus Region (Germany)

The most important parameter affecting ground-penetrating radar （GPR） measurements is the complex effective relative permittivity εr^＊,eff because it controls the propagation velocity and the reflection of GPR pulses. Knowing εr^＊,eff of soils passed through by electromagnetic waves increases accuracy in soil thickness and interface identification. Complex effective relative permittivity εr^＊,eff= εr^＊,eff - jεr^＊,effof 25 soil samples with textures ranging from loamy sand to silty clay was measured using the two-electrode parallelplate method. The measurements were conducted at defined water contents for frequencies from 1 MHz to 3 GHz. The results confirm the frequency dependence of εr^＊,eff and show that the dielectric behavior of soil-water mixtures is a function of water content. Applying the experimental data of this study with predictions based on the empirical model by Toppet aL （1980）, we find that Topp et aL＇s curve tends to underestimate the real part of εr^＊,eff measured. Along with frequency and water content, soil texture and organic matter affect soil permittivity. Moreover, the real part of εr^＊,eff increases at higher dry bulk densities. Output from our calibration model enables us to predict εr^＊,eff for the soil samples which were tested under the actual in situ soil water content. This results in high accuracy of soil thickness prediction.

Crevice Corrosion of K60 in Dry Desertification Saline Soil

Corrosion products of K60crevice samples which were buried in Ordos area were analyzed by scanning electron microscopy and X-ray diffraction.The result showed that,the corrosion potential decreased differently in the crevice and a maximum negative existed at the bottom side;with pH value reduced,the dissolved oxygen was nearly exhausted in the crevice.When the opening side of the coupons was coupled with each other,the crevice corrosion in the crevice might be accelerated and the pH value gradually reduced;however,the oxygen was not completely exhausted.The unbalanced current density between anode and cathode was the main cause of blocked self-catalysis effect in the crevice,and was also the main cause of corrosion of alloys.Lumpy corrosion happened on the surface of metal,and rusty layer was composed of Fe3O4,Fe2O3,FeO,FeOOH and FeS which distributed in the opening of crevice.There were the reddish-brown corrosion products and white matter which distributed in the form of filiform and spotted in the center part of crevice.The analysis showed that the white matter might include oxide of Fe and NaHCO3.

Design and experimental validation of improved grapevine burying machine

In order to address the low soil breaking rate,poor soil covering performance,and low working efficiency of the existing 3MT-1.8 and PMT-75 grapevine burying machines,two types of improved burying machines,namely the 3MTLJ-1.8 and 3MTXP-1.8,were developed in consideration of the local Ningxia soil conditions.Field experimental results indicated that the soil breaking rate of the 3MTLJ-1.8 machine was 71.44%,and its soil sampling volume increased by approximately 30%compared to that of the 3MT-1.8 machine.It was verified that the self-developed 3MTLJ-1.8 machine can be used in the southern regions of Ningxia.Furthermore,the soil sampling volume of the 3MTXP-1.8 burying machine was 0.24 m^(3)/m,and its soil breaking rate increased by more than 41.42%compared to the standard required volume.The 3MTXP-1.8 machine can be used in the northern areas of Ningxia,where the soil hardness is higher.The results can provide a reference for the development and popularization of grapevine burying machines in Ningxia.