Support pressure for circular tunnels in two layered undrained clay

To estimate the required support pressure for stability of circular tunnels in two layered clay under undrained condition,numerical solutions are developed by performing finite element lower bound limit analysis in conjunction with second-order cone programming.The support system is assumed to offer uniform internal compressive pressure on its periphery.From the literature,it is known that the stability of tunnels depends on the overburden pressure acting over it,which is a function of undrained cohesion and unit weight of soil,and cover of soil.When a tunnel is constructed in layered undrained clay,the stability depends on the undrained shear strength,unit weight,and thickness of one layer relative to the other layer.In the present study,the solutions are presented in a form of dimensionless charts which can be used for design of tunnel support systems for different combinations of ratios of unit weight and undrained shear strength of upper layer to those of lower layer,thickness of both layers,and total soil cover depth.

SYNTHESIS，CHARCTERIZATION AND CATALYTIC RESEARCH OF THE NEW TYPE LAYERED MICROPOROUS MATERIAL－ZnAl ANION CLAY PILLARBD BY GaW_9Fe_3

In this paper. tungstogallic heteropolyaniou trisubstituted with transition metal ferrum GaW9Fe3 was intercalated into ZnAl-NO3 type anion clay by means of ion-exchange for the first time. XRD patterns show that the pillated derivative possesses a gallery height of 0.98nm. IR spectra exhibit that the Keggin structure of intercalated heteropolyanion is remained. The new material was found to be catalytically efficient for the esterification of phthalic anhydride with 2-ethyl hexanol.

Layered Clay-Alginate Composites for the Adsorption of Anionic Dyes: A Biocompatible Solution for Water/Wastewater Treatment

Adsorption properties of layered anionic clay-composites for the removal of anionic dyes from water were studied. The dye adsorption capacities of the composites were higher than the pristine clay. The clay-alginate composite with 5.9% alginate showed highest adsorption for both the dyes. The maximum adsorption capacity of the composite was enhanced by 51% for Acid Green 25 and 160% for Acid Green 27, compared to the pristine layered clay sample. The adsorption isotherm data were fitted to the Langmuir, Freundlich and Temkin isotherm models. The isotherm data could be explained well using the Freundlich isotherm model. Adsorption kinetics was analyzed using normal first order and Lagergren first order kinetic models.

Simple Preparation of Halogen-Substituted <i>α</i>-Diimine Nickel Complexes Immobilized into Clay Interlayer as Catalysts for Ethylene Oligo-/Polymerization

In the practical use for the production of the α-olefins, it is highly desired to develop a novel heterogeneous catalyst system. The metal complexes immobilized into the clay interlayers show a great potential as heterogeneous catalysts due to their excellent processability. In this study, nine types of heterogeneous procatalyst Ln/Ni2+-micas were synthesized via a one-pot preparation method, which includes both the condensation reaction of the ligand derivatives and the intercalation of the ligands into the Ni2+ ion-exchanged fluorotetrasilicic mica interlayer. The ligand structures of the prepared procatalysts were [Ln: R-N = C(Nap)-C(Nap) = N-R] [(Nap = 1,8-naphthdiyl) (L1, R = 2-MePh;L2, R = 2-FPh;L3, R = 2-BrPh;L4, R = 4-MePh;L5, R = 4-FPh;L6, R = 4-BrPh;L7, R = 2,4-F2Ph;L8, R = 2,4-Br2Ph;L9, R = 2,6-F2Ph). At 50℃ and 0.7 MPaethylene pressure, the triisobutylaluminum-activated L1-L6/Ni2+-mica showed a catalytic activity for the ethylene oligo-/polymerization in the range of 334 - 549 g-ethylene&bull;g-cat–1&bull;h–1. A high catalyst activity was obtained when the substituent having a larger steric bulk than that of a methyl substituent was introduced at the ortho-position of the aryl rings. The introduction of the fluorine substituent as a strong electron-withdrawing group to the para-position also increased the catalytic activity. The L2, L4, L5, and L6/Ni2+-micas showed moderate selectivities to oligomers consisting of C4-C20 in the range of 19.9 - 41.6 wt% at 50℃. The calculated Schulz-Flory constants α based on the mole fraction of C12 and C14 were within 0.61 - 0.78.

Bearing Capacity and Critical Punch-Through Depth of Spudcan on Sand Overlying Clay

Spudcan may experience punch-through failure on strong over weak layered soils, such as sand overlying clay. A large deformation finite element method （LDFE） is used to simulate the penetration process of spudcan into sand overlying clay. The sand is simulated by smoothed hyperbolic Mohr-Coulomb model, and the clay is simulated by a simple elasto-plastic model which obeys Tresca yield criterion. According to the LDFE results of a large amount of cases, the effects of the strength, unit weight and thickness of the top sand layer, as well as the effect of the strength of the underlying clay on the spudcan punch-through behavior, are investigated. The critical depth occurring punch-through and the critical bearing capacity are presented in charts. Fitting equations to calculate the critical punch-through depth and the critical bearing capacity are proposed for the convenience of engineering practice.

Fe saponite, a layered silicate for reversible lithium-ions storage with large diffusion coefficient

A kind of layered Li;MSiO;material,Fe saponite with Na;pillaring (Na^(+)-FSAP) was developed as a lowcost and environment-friendly lithium-ion storage material.The Na^(+)-FSAP follows the insertion/deinsertion working mechanism accompanied by valence change of Fe from Fe^(1.86+) to Fe^(2.71+) (average value) after stabilization,and displays a specific capacity of 125 m Ah g^(-1) at 50 m A g^(-1) with retention ratio of 80.8%after 75 cycles.The Na^(+)-pillaring effect and abundant structural water in the gallery urge Li^(+) migrate rapidly,resulting in a large Li^(+) diffusion coefficient within a range of 10^(-6.5)–10^(-7.5) cm^(2)s^(-1).Thus,the Na^(+)-FSAP provides a model material to design electrode materials with rapid lithium-ion migration and has great potential to take place of polyanionic-type Li_(2)MSiO_(4)(M=Mn,Fe,Co) cathode materials.

Preparation,Characterization and Application of ZnAlLa-Hydrotalcite-Like Compounds

The preparation of ZnAlLa-hydrotalcite-like compounds [ZnAlLa-HTLcs] wasstudied. ZnAlLa-HTLcs were synthesized by a method of variable pH with the raw materials ofZn(NO_3)_2, Al(NO_3)_3, La(NO_3)_3, and NaOH. The eS'ccts of some factors (i.e. pH values, the moleratio of Al^(3+) to La^(3+), temperature and the period of hydrothermal treatment) on thepreparation of HTLcs were discussed systematically. XRD, TG-DTA, FT-IR spectroscopy, and ICP wereperformed to characterize ZnAlLa-HTLcs samples, and the thermal stability of HTLcs was alsodiscussed. It was shown that unique ZnAlLa-HTLcs with high crystallinity can be prepared, under theconditions of pH = 5.5-6.5, n(Zn^(2+))/n(Al^(3+) + La^(3+))=2 and the atomic ratio of La^(3+) toAl^(3+) ranging from 0.07 to 2, hydrothermal treatment at 120 ℃ for 5 h. When the calcination ofthe HTLcs is performed at temperatures above 200 ℃, ZnO phase is detected with Al_2O_3 and La_2O_3spreading on its top. The complex metal oxides derived from ZnAlLa-HTLcs at 500 ℃ have highercatalytic activity and selectivity than those from ZnAl-HTLcs for the esterification of acetic acidwith n-butanol under the same reaction conditions.

Linkage of microbial living communities and residues to soil organic carbon accumulation along a forest restoration gradient in southern China

Background:Forest restoration has been considered an effective method to increase soil organic carbon(SOC),whereas it remains unclear whether long-term forest restoration will continuously increase SOC.Such large uncertainties may be mainly due to the limited knowledge on how soil microorganisms will contribute to SOC accumulation over time.Methods:We simultaneously documented SOC,total phospholipid fatty acids(PLFAs),and amino sugars(AS)content across a forest restoration gradient with average stand ages of 14,49,70,and>90 years in southern China.Results:The SOC and AS continuously increased with stand age.The ratio of fungal PLFAs to bacterial PLFAs showed no change with stand age,while the ratio of fungal AS to bacterial AS significantly increased.The total microbial residue-carbon(AS-C)accounted for 0.95-1.66% in SOC across all forest restoration stages,with significantly higher in fungal residue-C(0.68-1.19%)than bacterial residue-C(0.05-0.11%).Furthermore,the contribution of total AS-C to SOC was positively correlated with clay content at 0-10 cm soil layer but negatively related to clay content at 10-20 cm soil layer.Conclusions:These findings highlight the significant contribution of AS-C to SOC accumulation along forest restoration stages,with divergent contributions from fungal residues and bacterial residues.Soil clay content with stand age significantly affects the divergent contributions of AS-C to SOC at two different soil layers.

Syntheses, characterization and catalytic reactivities of heteropolyanion-pillared clay of anions of Zn-Al type

Mono-substituted Keggin ions PW11O39Cr(H2O)4 , PW11TiO403 and PW11VO404 were intercalated between the layers of the clay of anions of Zn-Al type using the ion exchange method to obtain a new type of pillared layered microporous materials ZnAl-PW11Cr, ZnAl-PW11Ti and ZnAl-PW11V with basal spacing (1.48±0.02) run. On the basis of the MAS NMR results of 27A1 and 31P, a steric pillared layered structure model of orientation localization of PW11VO40,4- in the orientation in which the C2 axis of PW11VO404-is perpendicular to the host layer. It has been found that this kind of pillared layered microporous materials possess a higher catalytic activity for the esterification of acetic acid with n-butanol than H-type molecular sieves.

The unmediated choline sensor based on layered double hydroxides in hydrogen peroxide detection mode

In this work,we have developed a novel choline biosensor on the basis of immobilization of choline oxidase (ChOx) by the attractive materials layered double hydroxides (LDHs). Amperometric detection of choline was evaluated by holding the modified electrode at 0.5 V (vs. SCE). Due to the special properties of LDHs ([Zn3-Al-Cl]),such as chemical inertness,high porosity,and swelling property,the [Zn3-Al-Cl]/ChOx modified electrode exhibited an enhanced analytical performance. The biosensor provided a linear response to choline over a concentration range from 3.7 × 10-6 to 6.3 × 10-4 M with a low detection limit of 3 × 10-7 M based on S/N=3. The apparent Michaelis-Menten constant was calculated to be 1.38 mM. In addition,the interaction between ChOx and LDHs has also been investigated using FT-IR spectroscopy.

BioClay^(TM)prolongs RNA interference-mediated crop protection against Botrytis cinerea

One of the most promising tools for the control of fungal plant diseases is spray-induced gene silencing(SIGS).In SIGS,small interfering RNA(siRNA)or double-stranded RNA(dsRNA)targeting essential or virulence-related pathogen genes are exogenously applied to plants and postharvest products to trigger RNA interference(RNAi)of the targeted genes,inhibiting fungal growth and disease.However,SIGS is limited by the unstable nature of RNA under environmental conditions.The use of layered double hydroxide or clay particles as carriers to deliver biologically active dsRNA,a formulation termed BioClay^(TM),can enhance RNA durability on plants,prolonging its activity against pathogens.Here,we demonstrate that dsRNA delivered as BioClay can prolong protection against Botrytis cinerea,a major plant fungal pathogen,on tomato leaves and fruit and on mature chickpea plants.BioClay increased the protection window from 1 to 3 weeks on tomato leaves and from 5 to 10 days on tomato fruits,when compared with naked dsRNA.In flowering chickpea plants,BioClay provided prolonged protection for up to 4 weeks,covering the critical period of poding,whereas naked dsRNA provided limited protection.This research represents a major step forward for the adoption of SIGS as an eco-friendly alternative to traditional fungicides.

Characterization of Sediment from Ourokessoum, North Cameroon: Morphostructural, Mineralogical, and Physicochemical Properties

The present study examines the morphological, physicochemical, and mineralogical specificity of clay sediments in the Hamakoussou Basin with the objective of exploring their potential applications. Field data collection was followed by a series of physicochemical and mineralogical tests on the clay samples. Results show that the clay layers, which range in thickness from 11 - 120 cm, exhibit gray, yellowish, or greenish colors. From a physicochemical perspective, these clay layers are found to be basic with a pH ranging from 8.5 for the higher Hama2 layer to 7.6 for the lower Hama1 layer. The sum of exchangeable bases (S) is medium to high with higher values in the Hama1 layer (53.45 meq/100g) and lower values in the Hama3 layer (17.09 meq/100g). Similarly, the cation exchange capacity (CEC) varies from 62.32 meq/100g for the higher Hama1N4 clay layer to 35.6 meq/100g for the lower Hama1N3 clay layer. Mineralogically, the clay materials are primarily composed of smectites, with illite, kaolinite, calcite, quartz, feldspar, hematite, and goethite also present. This study emphasizes the versatility of clay in various industries and scientific domains. It is known for its impermeability, plasticity, and fossil-preserving capabilities, making it a valuable material for economic, practical, and academic applications.

Mechanics of Aquitard Drainage by Aquifer-System Compaction and Its Implications for Water-Management in the North China Plain

The deformation of aquitard is the main contribution to land subsidence in the North China Plain, and the water released from aquitard compaction may be a large portion of the exploited groundwater. In this study, the consolidation test was employed to understand the mechanics on the drainage and deformation of aquitard. The results suggested the strain of aquitard mainly resulted from the difference of hydraulic head between aquifers. And it was decreased with depth of aquitard at the same hydrodynamic pressure. In contrast with the interbed within aquifers, the aquitard was deformable when it was compressed. The weakly bound water was significantly released when the void ratio was about 0.44–0.45, and the EC of water released from the aquitard was decreased with the compacting process. The data from the consolidation test suggested that the pumping of groundwater from aquifer III might be less contribution to the land subsidence with respect to other aquifers in the future.