Enhanced Hoek-Brown(H-B)criterion for rocks exposed to chemical corrosion

Underground constructions often encounter water environments,where water–rock interaction can increase porosity,thereby weakening engineering rocks.Correspondingly,the failure criterion for chemically corroded rocks becomes essential in the stability analysis and design of such structures.This study enhances the applicability of the Hoek-Brown(H-B)criterion for engineering structures operating in chemically corrosive conditions by introducing a kinetic porosity-dependent instantaneous mi(KPIM).A multiscale experimental investigation,including nuclear magnetic resonance(NMR),X-ray diffraction(XRD),scanning electron microscopy(SEM),pH and ion chromatography analysis,and triaxial compression tests,is employed to quantify pore structural changes and their linkage with the strength responses of limestone under coupled chemical-mechanical(C-M)conditions.By employing ion chromatography and NMR analysis,along with incorporating the principles of free-face dissolution theory accounting for both congruent and incongruent dissolution,a kinetic chemical corrosion model is developed.This model aims to calculate the kinetic porosity alterations within rocks exposed to varying H+concentrations and durations.Subsequently,utilizing the generalized mixture rule(GMR),the kinetic porositydependent mi is formulated.Evaluation of the KPIM-enhanced H-B criterion using compression test data from 5 types of rocks demonstrated a high level of consistency between the criterion and the experimental results,with a coefficient of determination greater than 0.96,a mean absolute percentage error less than 4.84%,and a root-mean-square deviation less than 5.95 MPa.Finally,the physical significance of the porosity-dependent instantaneous mi is clarified:it serves as an indicator of a rock’s capacity to leverage the confining pressure effect.

Quantifying the Mechanical Properties of White Sandstone Based on Computer Fractal Theory

The work presented in this paper was conducted to quantify the relationship between the pore characteristics and mechanical properties of white sandstone.The study include tests carried out under the coupling effects of chemical corrosion,temperature,nuclear magnetic resonance,and mechanical tests.Computer fractal theory was employed to describe and quantify the characteristics of the growth of pores in white sandstone under the same coupling effect.A custom developed program code,in the MATLAB software platform,was used for calculating the growths of the pores in white sandstone when subjected to coupling effects.The correlation between the computer fractal dimension of the growth of the pores in rock and characteristics of mechanical damage was accordingly analyzed.The results showed that when the temperature was set at a level lower than 100°C,it caused damage to the rock and strength reduction,primarily due to the rates of chemical reactions,the generation,and evolution of pores in the rock mass under the coupling effects of chemical corrosion and temperature.Overall,it was observed that the higher the value of the computer fractal dimension,the higher the growth of the pores,and the lower the uniaxial compressive strength of the white sandstone.

Study on the Corrosion inhibitor and Fog Suppressor for Chemical Pickling of Iron and Steel

A new type of corrosion inhibitor and fog suppressor composed of Nitrogen-containing alkaloid,water-soluble butadiene lower polymer, and inorganic electrolyte has been investigated by gravimetric and electrochemical method. Effects or this chemicals on pickling rate and hydrogen penetration into iron and steel material in 50～150 g/L HCI or/and H2SO4 solutions at 20～70℃ temperature were examined. The amount of acid fog escaping from the surface of air-liquid was determined by chemical titration. The results indicate that the efficiency of inhibition and suppression depends on film properties by which mean a barrier film on the interface of bare mild steel/solution or an unsolvable liquid membrane as hydrophibic effect.In present work the film-forming mechanism by in situ and chemistry-mechanics effect is also discussed.

In situ construction of zinc-rich polymeric solid–electrolyte interface for high-performance zinc anode

With their excellent reliability and environmental friendliness,zinc-ion batteries(ZIBs)are regarded as potential energy storage technologies.Unfortunately,their poor cycling durability and low Coulombic effectiveness(CE),driven by dendritic growth and surface passivation on the Zn anode,severely restrict their commercialization.Herein,we describe the in situ construction of a Zn-rich polymeric solid–electrolyte interface(SEI)using poly-acrylic acid(PAA)as an electrolyte additive.On the one hand,the PAA SEI layer offers evenly distributed nucleation sites and promotes ion transport,hence suppressing dendrite growth.On the other hand,the SEI layer prevents direct contact between the Zn foil and the electrolyte,thus inhibiting side reactions.Additionally,the robust coordination of PAA with Zn^(2+)and the SEI layer's good adherence to the Zn foil provide long-term pro-tection to the Zn anode.As a result,symmetric cells and Zn/V_(2)O_(5)cells all deliver prolonged cycle life and superior electrochemical efficiency.

Estimates of strength and cracking behaviors of pre-flawed granite specimens treated by chemical corrosion under triaxial compression tests

Four types of granite specimens were prepared and treated by chemical corrosion for 5 and 30 days,which were then used to carry out triaxial compression tests under different confining pressuresσ_(3).Type A is the intact sample with no preexisting flaws.Types B and C are the samples containing two relatively low-dip flaws and two relatively high-dip flaws,respectively.Type D is the sample including both relatively low-dip and relatively high-dip flaws.The influences of pH value of chemical solutions,flaw distribution,corrosion time andσ_(3) on triaxial stress-strain curves and ultimate failure modes are analyzed and discussed.The results show that the pH value of the chemical solution,corrosion time and the arrangement of preexisting flaws play crucial roles in the cracking behaviors of granite specimens.Type A specimens have the largest peak axial deviatoric stress,followed by Type C,Type D,and Type B specimens,respectively.It is because the decrease in the inclination of preexisting flaws induces the weakening effect due to the decrease in the shadow area along the compaction direction.Under aσ_(3) of 5 MPa,the peak axial deviatoric stress drops by approximately 40.89%,29.08%,4.08%,and 23.53%for pH=2,4,7,and 12,respectively.For intact granite(Type A)specimens,the ultimate failure mode displays a typical shear mode.The connection of two secondary cracks initiated at the tips of preexisting cracks is always the ultimate failure and crack coalescence mode for Type B specimens.The ultimate failure and crack coalescence mode of Types C and D specimens are significantly affected by pH value of the chemical solution,corrosion time andσ_(3),which is different from those of Types A and B specimens due to the differences in flow distributions.