Maximum Excess Research Articles

Temperature Cycling Induced Deracemization of p-Synephrine in the Presence of Degradation.

The acquisition of enantioenriched organic molecules is crucial in processes where the enantiomeric purity of active ingredients impacts efficacy and safety. Temperature cycling-induced deracemization (TCID) can achieve deracemization, but its effectiveness can be hindered by degradation reactions that influence the kinetics and the achievable enantioenrichment. This work characterizes the impact of degradation on the dynamic development of enantiomeric excess during the TCID process for the p-synephrine hydrochloride salt. The pilot study demonstrates that a maximum enantiomeric excess of 86% R-(-)-p-synephrine can be achieved at an intermediate batch time among all tested conditions. Degradation promoted the crystallization of a dimer with novel solid-state form, disynephrine ether dihydrochloride, which led to a substantial decrease in the slurry density of synephrine, potentially contributing to the observed decline in enantiomeric excess during the TCID process. Batch-to-batch variability in process dynamics and maximum attainable enantiomeric excess was observed, potentially attributable to the sensitivity of the process to uncontrolled initial conditions. These findings underscore the importance of accounting for degradation kinetics in the design and optimization of TCID processes for enantioenrichment.

Holistic shape variation of the rib cage in an adult population.

Traumatic injuries to the thorax are a common occurrence, and given the disparity in outcomes, injury risk is non-uniformly distributed within the population. Rib cage geometry, in conjunction with well-established biomechanical characteristics, is thought to influence injury tolerance, but quantifiable descriptions of adult rib cage shape as a whole are lacking. Here, we develop an automated pipeline to extract whole rib cage measurements from a large population and produce distributions of these measurements to assess variability in rib cage shape. Ten measurements of whole rib cage shape were collected from 1,719 individuals aged 25-45years old including angular, linear, areal, and volumetric measures. The resulting pipeline produced measurements with a mean percent difference to manually collected measurements of 1.7% ± 1.6%, and the whole process takes 30s per scan. Each measurement followed a normal distribution with a maximum absolute skew value of 0.43 and a maximum absolute excess kurtosis value of 0.6. Significant differences were found between the sexes (p < 0.001) in all except angular measures. Multivariate regression revealed that demographic predictors explain 29%-68% of the variance in the data. The angular measurements had the three lowest R2 values and were also the only three to have little correlation with subject stature. Unlike other measures, rib cage height had a negative correlation with BMI. Stature was the dominant demographic factor in predicting rib cage height, coronal area, sagittal area, and volume. Subject weight was the dominant demographic factor for rib cage width, depth, axial area, and angular measurements. Age was minimally important in this cohort of adults from a narrow age range. Individuals of similar height and weight had average rib cage measurements near the regression predictions, but the range of values across all subjects encompassed a large portion of their respective distributions. Our findings characterize the variability in adult rib cage geometry, including the variation within narrow demographic criteria. In future work, these can be integrated into computer aided engineering workflows to assess the influence of whole rib cage shape on the biomechanics of the adult human thorax.

Undrained triaxial tests of underconsolidated overlying sediments of hydrate deposits in the South China Sea

The South China Sea (SCS) is an important repository for natural gas hydrates (NGHs), where some NGH deposits and their overlying sediments (OSs) are in an underconsolidated state. During the exploitation of NGHs, the stability of the OSs of the NGH deposits is one of the key factors in ensuring mining safety. Especially under different consolidation degrees, the mechanical response and stability of the OSs will vary, which directly affects the safety and efficiency of the NGH mining. This research explores the influence of different consolidation degrees on the mechanical properties of the OSs of NGH deposits in the SCS. The strength and pore pressure characteristics were analyzed through undrained triaxial shear tests. The findings indicate that an increase in consolidation degree enhances the strain softening behavior, and an increase in initial effective stress enhance the strain hardening and shear contraction behaviors of the samples. The failure strength, modulus, and maximum excess pore pressure increase with the consolidation degree and initial effective stress, and there is an approximately linear correlation between failure strength and consolidation degree. Therefore, the exploitation of NGHs in the SCS must comprehensively consider the burial depth and consolidation degree of the OSs. The findings of this study will assist in optimizing mining plans and enhancing safety during the exploitation process.

Factors influencing nonstandard piezocone dissipation curves and interpreting the coefficient of consolidation

Piezocone dissipation curves can be categorized as standard (monotonic) or nonstandard (nonmonotonic) curves. However, most methods to evaluate the horizontal coefficient of consolidation (ch) from piezocone dissipation tests are only applicable to standard dissipation curves. The factors that influence nonstandard piezocone dissipation curves were numerically investigated, and a method to interpret the ch from nonstandard dissipation curves was proposed. Nonstandard dissipation curves appear if the maximum excess pore pressure is located some distance away from the pore pressure sensor (sensor located on the cone shoulder or penetration in overconsolidated soils) when the penetration is halted to carry out the dissipation test. Some factors result in more marked nonstandard dissipation phenomena, e.g., a larger overconsolidation ratio (OCR) and a smaller horizontal permeability (kh). Assuming that the ch calculated based on the time for 50 % dissipation of the maximum excess pore pressure (t50) from the standard dissipation curve by the existing method is the “real” value, an equation for correcting t50 from nonstandard dissipation curves was proposed based on the initial value of excess pore pressure (ui), the maximum value of excess pore pressure (umax) and the time for reaching the maximum excess pore pressure (tumax). The ch values interpreted by the corrected t50 (t50c) were larger than those interpreted by the method of shifting log t and were more representative of the actual ch values in the field.

Statistical characterization of the effect of random core loss on the intercore crosstalk in long-haul uncoupled multicore fiber links

We characterize the statistical properties of direct average intercore crosstalk (ICXT) in long-haul uncoupled multicore fiber (MCF) links consisting of concatenated MCF segments, where core dependent loss (CDL) in each segment varies randomly. Numerical simulation results show that the direct average ICXT power at the output of long-haul MCF links with random CDL is well described by a Gaussian distribution. A statistical distribution, which accounts for only two values of core loss (the highest and lowest core loss) with equal probability, is proposed as the worst-case distribution of core loss resulting in the maximum excess of direct average ICXT power. With this distribution, practical values of random CDL, 20 MCF segments per span and 2000 km-long links, analytical and simulation results show the maximum excess of direct average ICXT power does not exceed 0.25 dB, being further lower for a higher number of segments. An analytical approximation for the maximum excess of direct average ICXT power in long-haul uncoupled MCF links with similar spans is presented. Demonstrating high accuracy (with less than 0.02 dB discrepancy relative to simulation results in all cases evaluated), this approximation provides a simple and efficient means for estimating the worst-case impact of random CDL on ICXT power in long-haul MCF links.

What can be learnt from UHECR anisotropies observations

Context. Various signals of anisotropy of the ultra-high-energy cosmic rays (UHECRs) have recently been reported, whether at large angular scales, with a dipole modulation in right ascension observed in the data of the Pierre Auger observatory (Auger), as discussed in the first paper accompanying the present one, or at intermediate angular scales, with flux excesses identified in specific directions by Auger and the Telescope Array (TA) Collaborations. Aims. We investigated the implications of the current data regarding these intermediate scale anisotropies, and examined to what extent they can be used to shed light on the origin of UHECRs, and constrain the astrophysical and/or physical parameters of the viable source scenarios. We also investigated what could be learnt from the study of the evolution of the various UHECR anisotropy signals, and discussed the expected benefit of an increased exposure of the UHECR sky using future observatories. Methods. We simulated realistic UHECR sky maps for a wide range of astrophysical scenarios satisfying the current observational constraints, with the assumption that the UHECR source distribution follows that of the galaxies in the Universe, also implementing possible biases towards specific classes of sources. In each case, several scenarios were explored with different UHECR source compositions and spectra, a range of source densities and different models of the Galactic magnetic field. We also implemented the Auger sky coverage, and explored various levels of statistics. For each scenario, we produced 300 independent datasets on which we applied similar analyses as those recently used by the Auger Collaboration, searching for flux excesses through either blind or targeted searches and quantifying correlations with predefined source catalogues through a likelihood analysis. Results. We find the following. First, with reasonable choices of the parameters, the investigated astrophysical scenarios can easily account for the significance of the anisotropies reported by Auger, even with large source densities. Second, the direction in which the maximum flux excess is found in the Auger data differs from the region where it is found in most of our simulated datasets, although an angular distance as large as that between the Auger direction and the direction expected from the simulated models at infinite statistics, of the order of ∼20°, occurs in ∼25% of the cases. Third, for datasets simulated with the same underlying astrophysical scenario, and thus the same actual UHECR sources, the significance with which the isotropy hypothesis is rejected through the Auger likelihood analysis can be largest either when ‘all galaxies’ or when only ‘starburst’ galaxies are used to model the signal, depending on which model is used to model the Galactic magnetic field and the resulting deflections. Fourth, the study of the energy evolution of the anisotropy patterns can be very instructive and provide new astrophysical insight about the origin of the UHECRs. Fifth, the direction in which the most significant flux excess is found in the Auger dataset above 8 EeV appears to essentially disappear in the dataset above 32 EeV, and, conversely, the maximum excess at high energy has a much reduced significance in the lower energy dataset. Sixth, both of these appear to be very uncommon in the simulated datasets, which could point to a failure of some generic assumption in the investigated astrophysical scenarios, such as the dominance of one type of source with essentially the same composition and spectrum in the observed UHECR flux above the ankle. Seventh, given the currently observed level of anisotropy signals, a meaningful measurement of their energy evolution, say from 10 EeV to the highest energies, will require a significant increase in statistics and a new generation of UHECR observatories.

Enantioselective liquid-liquid extraction of 2-cyclohexylmandelic acid enantiomers using chiral ionic liquids.

Obtaining optically pure compounds in an eco-friendly and cost-efficient manner plays an important role in human health and pharmaceutical industry. Racemic separation using multistage stereoselective liquid-liquid extraction has become one of the most practical and effective approach to access homochiral enantiomers. Currently, chiral ionic liquids (CILs) with structural designability have become a promising chiral additive and enable them as adjustable candidates for racemic separation. Herein, a high-effective stereoselective liquid-liquid extraction process composed of imidazolium cations and amino acid-derived anions as the chiral additive was established for racemic 2-cyclohexylmandelic acid (CHMA) separation. We have systematically investigated the choice of organic solvent, concentration of CIL, extraction temperature, and the pH of aqueous phase. For three-stage stereoselective extraction, the maximum enantiomeric excess (e.e.) for CHMA was reached up to 40.6%. Furthermore, the mechanism of steric effect and stereoselective capacity between the CILs and racemic CHMA was discussed and simulated. We envision that the work will facilitate the development of CILs in multistage liquid-liquid extraction and promote the large-scale production of optically pure enantiomers.

Influence of repeated surface surcharge loading on tunnel displacement considering the structural characteristics of soft clay

Shanghai soft clay is a typical marine clay with specific structural characteristics. However, the effects of surface surcharge loading on structured soft clay and existing tunnels remain unclear. In this study, the effect of repeated surface surcharge loading on tunnel displacement was numerically investigated, considering the structural characteristics of Shanghai Layer 4 soft clay. An elastoplastic constitutive model (Shanghai model) that describes the mechanical properties and structural characteristics of natural clay was used to simulate the soil response. The results indicate that the first cycle of repeated surface surcharge loading had the greatest effect on the displacement of the tunnel and overlying clay; subsequent loading cycles further increased the displacement. With repeated surface surcharge loading, the displacement of the overlying clay exhibited a significant decreasing trend with increasing depth. The maximum excess pore pressure of the clay exhibited a decreasing trend with increasing loading time. The displacements of the tunnel and overlying clay were greater when the effects of the soil structure were considered. However, the initial degree of the structure had no significant effect on the accumulation of excess pore pressure when the surface surcharge loading did not reach the ultimate bearing capacity of the clay.

Numerical investigation on the effect of repeated surface surcharge loading on soil deformation and tunnel displacement in structured soft clay

Shanghai soft clay is a typical marine clay with specific structural characteristics. The tunnel and overlying soft clay may undergo repeated surface surcharge loading, such as the temporary soil stacking. Assessing the extent of structured soft clay deformation and tunnel displacement caused by repeated surface surcharge loading is of great significance for evaluating of the safety of ground structures and underground tunnels. In this study, the effects of repeated surface surcharge loading on the soil and tunnel displacement were numerically investigated. The finite element code DBLEAVES with an elasto-plastic constitutive model (Shanghai model) that describes the mechanical properties and structural characteristics of natural clay was used to simulate the soil response. The parameters of the constitutive model were obtained through geotechnical testing. The effects of the soil structural characteristics, seepage conditions, and loading conditions on the soil response and tunnel displacement were analyzed. The numerical results show that the maximum excess pore pressure of clay decreased as the number of loading cycles increased. The effects of the structural characteristics cause greater displacement, whereas the effects of the degradation parameters of the structure are more significant than the initial degree of the structure. The differences in the vertical displacement of the tunnel and overlying soils owing to the structural characteristics become apparent with an increase in surface surcharge loading. However, the effects of structural characteristics become less significant as the depth increases. The seepage conditions and loading method primarily affect the build-up of excess pore pressure and the development of effective stress paths. For soils inside the surcharge area, a flexible surcharge produces a greater vertical displacement than a rigid surcharge. As the burial depth increased, the effects of the seepage conditions and loading method showed a declining tendency.

Oxygen consumption rate during recovery from loss of equilibrium induced by warming, hypoxia, or exhaustive exercise in rainbow darter (Etheostoma caeruleum).

Animals routinely encounter environmental (e.g., high temperatures and hypoxia) as well as physiological perturbations (e.g., exercise and digestion) that may threaten homeostasis. However, comparing the relative threat or "disruptiveness" imposed by different stressors is difficult, as stressors vary in their mechanisms, effects, and timescales. We exploited the fact that several acute stressors can induce the loss of equilibrium (LOE) in fish to (i) compare the metabolic recovery profiles of three environmentally relevant stressors and (ii) test the concept that LOE could be used as a physiological calibration for the intensity of different stressors. We focused on Etheostoma caeruleum, a species that routinely copes with environmental fluctuations in temperature and oxygen and that relies on burst swimming to relocate and avoid predators, as our model. Using stop-flow (intermittent) respirometry, we tracked the oxygen consumption rate (MO2) as E. caeruleum recovered from LOE induced by hypoxia (PO2 at LOE), warming (critical thermal maximum, CTmax), or exhaustive exercise. Regardless of the stressor used, E. caeruleum recovered rapidly, returning to routine MO2 within ~3 h. Fish recovering from hypoxia and warming had similar maximum MO2, aerobic scopes, recovery time, and total excess post-hypoxia or post-warming oxygen consumption. Though exhaustive exercise induced a greater maximum MO2 and corresponding higher aerobic scope than warming or hypoxia, its recovery profile was otherwise similar to the other stressors, suggesting that "calibration" to a physiological state such as LOE may be a viable conceptual approach for investigators interested in questions related to multiple stressors, cross tolerance, and how animals cope with challenges to homeostasis.

Sexual Constitution and Sexual Biography

Sexual constitution is one of the main factors that determines the severity of sexual desire. According to the definition of G. S. Vasilchenko (1977), “... the sexual constitution is a set of stable biological properties which are formed under the influence of hereditary factors and developmental conditions in the prenatal period and the period of early ontogenesis. Sexual constitution limits the range of individual needs at a certain level of sexual activity and characterizes individual resistance to pathogenic factors, which are characterized by selectivity to the sexual sphere”. The concept of “sexual constitution” has gained considerable popularity in specialized literature. To determine the sexual constitution of men, G. S. Vasilchenko developed and tested for the first time a scale for its vector definition, which takes into account seven indicators, namely: I vector – age of sexual libido awakening, II vector – age of first ejaculation, III vector – trochanteric index, IV vector – pattern of hair growth pubic area, V vector – maximum excess, VI vector – time between marriage and entry into the zone of conditional physiological rhythm (CPR), which is equal to two to three sexual acts per week, VII vector – the age of the man at which he switched to CPR. The first four vectors (I–IV) are closely related to the human genotype. They are used to determine the genotypic index of sexual constitution – Kg, which is the arithmetic mean of these vectors. V-VII vectors are used to determine the constitutionally modeled index of sexual activity (Ka). The arithmetic average of all seven vectors (I–VII) is called the phenotypic index of sexual constitution (Kf). After determining the values of all sexual constitution vectors, the Ka/Kg index is also determined, which makes possible to find how much a man’s sexual activity corresponds to his constitutional capabilities. Thus, this indicator in the group of persons “conditional norm” was 1.18. The article presents data on the female sexual constitution and the scale of its vector definition, which was developed and tested by I. L. Botneva (1983). Recommendations for determining the sexual constitution of a person are offered. In addition, the article provides clinical observations of the author, which testify to the influence of sexual biography on sexual activity in order to take it into account when determining this constitution.

Radiological Risk Assessment of Soil Using RESRAD-OFFSITE Code in Communities around Indorama Fertilizer Company Eleme, Port-Harcourt, Rivers State, Nigeria

Anthropogenic activities around a fertilizer company can cause elevation in the concentration of naturally-occurring radioactive materials (NORMs) within surrounding soils, as a result of effluent discharge or heaping of rocks used as raw materials. The aim of this study was to evaluate the human risk associated with exposure to NORMs in soils from communities around Indorama Fertilizer Company Eleme, Port-Harcourt, Rivers State, Nigeria. A sodium-iodide doped with thallium [NaI(TI)] detector was used to measure activity concentrations of these NORMs in 22 soil samples within the study area. The residual radioactivity (RESRAD) offsite modeling program(version 4.0) was then used to estimate the radiation doses and the cancer morbidity risk of uranium-238 (238U), thorium-232 (232Th) and potassium-40 (40K) for hypothetical resident farmer scenario. According to the RESRAD prediction, the maximum total effective dose equivalent (TEDE) during 100 years was found to be 2.82 x 10-5 mSvy-1 at year 12, while the maximum total excess cancer morbidity risk for all the pathways was 3.52E-08 at year 6. Therefore, results obtained from the RESRAD-OFFSITE code in this study has shown that the health risk from effluent discharge within the study area is within acceptable levels according to international standards.

ВОДНЫЙ БАЛАНС БЕЛАРУСИ И ЕГО ИЗМЕНЕНИЯ В РЕЗУЛЬТАТЕ ГЛОБАЛЬНОГО ПОТЕПЛЕНИЯ

Estimates of the water balance components (precipitation, evaporation, zonal and meridional advection of moisture) on the territory of Belarus for the cold (October-March) and warm (April-September) seasons have been obtained on the basis of the balance calculations of precipitation recycling and the ERA5 reanalysis data. It has been shown that the precipitation on the territory of Belarus results from westerlies in 77-84% of cases, from southerlies in 14-20% of cases, and from local evaporation in 2-4% of cases. Annual total precipitation exceeds annual evaporation by 18-30% (the maximum excess is observed in the north, and the minimum is registered in the southeast). During the warm seasons, there is a negative water balance in entire Belarus: evaporation exceeds precipitation by 8-23%. Over the period of global warming, the annual difference between precipitation and evaporation has decreased by 12-15%. The water balance for the warm season has decreased to negative values at the beginning of the current century due to the activation of summer warming. An increase in the amplitude of the water balance fluctuations has been revealed for the cold season, which indicates strengthening climate extremity.

Прогнозування динаміки розвитку тваринництва за допомогою часових рядів

The construction of time series using historical data is one of the urgent problems of management in the agrarian sector, since the analysis and forecasting of processes related to the food security of the State, of region, and of economic entities is crucial. With the help of forecasts, businesses can adjust their production activities in such a way as to meet demand and deliver products to consumers on time. The aim of this study is to forecast the dynamics of the development of stock of cattle and cows and to determine the optimal forecasting period. For this type of analysis, statistical methods related to autoregression are used: autoregressive models, moving average models, or combinations of both; integrated models with a variable structure, and models that include seasonal effects and exogenous factors with an autoregressive and moving average component in the model. Monthly statistics on the number of cattle and cows are provided: mean, standard deviation, minimum and maximum values, asymmetry and excess. The dynamics of decline in the number of stock of cattle and cows is shown. The studied series were tested for stationarity. To the time series of the number of cattle, the Box–Cox transformation was applied. The optimal parameters of the models used are presented. Forecast values for time intervals (months) have been obtained and changes in the number of stock of cattle over the past 17 years have been analyzed. The built time series are compared with the actual values, which is illustrated in the graphs. Estimates of standard deviation, mean absolute error for different forecasting terms are provided. When comparing these estimates for different time intervals, the optimal time period for the forecast (24 months) was determined. This study allows farms and enterprises of the industry to realize how much products (milk, meat) can be harvested or obtained in the future. This assists in taking the necessary managerial steps: plan for resource needs, improve efficiency, increase profits, reduce costs, and adapt to changes in the market.

The Effect Of Rye Translocation T1BL.1RS on economically valuable traits of winter common wheat varieties

There have been studied new promising winter common wheat varieties ‘Ambar’, ‘Premiera’ and ‘Ermak’, the leading variety according to the area occupied in the Rostov region. The variety ‘Don 107’ was used as a standard according to reserve protein loci to identify introgression of genetic material from rye, and there has been studied the effect of the translocation T1BL.1RS on the severity of grain quality traits. The samples were grown in a competitive variety testing conducted in the department of winter wheat breeding and seed production of the ARC “Donskoy” in 2017-2019. Estimations, records, and observations were carried out in accordance with the methodological instructions of the State Variety Testing of agricultural crops. In order to identify rye translocations, there has been used the method of electrophoresis of alcohol-soluble reserve proteins in an acidic medium in a starch gel. There has been determined that the mean productivity of the new promising variety ‘Ambar’ over the years of study exceeded the standard by 6%, and the variety ‘Ermak’ by 7%. The excess of maximum productivity was 5% and 23%, respectively, over the standard and the leading variety. The variety ‘Premiera’ has had mean productivity higher by 13 and 14% compared to the standard ‘Don 107’ and the variety ‘Ermak’, respectively. There has been established a maximum productivity excess to the standard and the leading variety by 3% and 9%. At the same time, their flour strength and SDS-sedimentation were 63% and 60%, 102% and 97%, respectively. According to protein and gluten percentage in grain, the varieties ‘Ambar’ and ‘Premiera’, like ‘Don 107’ and ‘Ermak’ have fallen into the same quality group of class 3, being characterized with valuable grain. An important advantage of the ‘varieties Ambar’ and ‘Premiera’ is resistance to brown rust, yellow rust, stem rust and powdery mildew, since the translocation contains resistance genes to these diseases.

Impact of Low-Temperature Water Exposure and Removal on Zeolite HY.

Aqueous-phase postsynthetic modifications of the industrially important Y-type zeolite are commonly used to change overall acid site concentrations, introduce stabilizing rare-earth cations, impart bifunctional character through metal cation exchange, and tailor the distribution of Brønsted and Lewis acid sites. Zeolite Y is known to undergo framework degradation in the presence of both vapor- and liquid-phase water at temperatures exceeding 100 °C, and rare-earth exchanged and stabilized HY catalysts are commonly used for fluidized catalytic cracking due to their increased hydrothermal resilience. Here, using detailed spectroscopy, crystallography, and flow-reactor experiments, we reveal unexpected decreases in Brønsted acid site (BAS) density for zeolite HY following exposure even to room-temperature liquid water. These data indicate that aqueous-phase ion-exchange procedures commonly used to modify zeolite Y are impacted by the liquid water and its removal, even when fractional heating rates and inert conditions much less severe than standard practice are used for catalyst dehydration. X-ray diffraction, thermogravimetric, and spectroscopic analyses reveal that the majority of framework degradation occurs during the removal of a strongly bound water fraction in HY, which does not form when NH4Y is immersed in liquid water and which leads to reduced acidity in HY even when dehydration conditions much milder than those typically practiced are employed. Na+-exchanged HY prepared via room-temperature aqueous dissolution demonstrates that Brønsted acid sites are lost in excess of the theoretical maximum that is possible from sodium titration. The structural impact of low-temperature aqueous-phase ion-exchange methods complicates the interpretation of subsequent data and likely explains the wide variation in reported acid site concentrations and catalytic activity of HY zeolites with high-Al content.

Synchronous Grouting Analysis of Shield Tunneling through High Water Pressure Fault Fracture Zone

Using numerical software to establish a three-dimensional geological model of shield tunneling through fault fracture zones, considering the synchronous grouting effect at the shield tail, the disturbance of various geotechnical structures in the fault fracture zone under deep burial and high water pressure conditions is studied. According to the comparison between the numerical model analysis results and the on-site inspection results of the entire process of Shiziyang B3 section, synchronous grouting at the shield tail is the main reason for the changes in soil and water pressure in the fault fracture zone area. The soil and water pressure changes strongly during shield tunneling, and the maximum excess pore pressure value occurs when the shield tail passes. When the shield tunneling machine is far away, the soil and water stress shows a downward trend. The impact of synchronous grouting decreases with the increase in tunneling distance. Due to the difference in permeability, the variation law of pore pressure in the fault fracture zone is significantly different from the original rock, leading to a faster increase in pore pressure in the fracture zone area and a wider range of influence.

Experimental approach for assessing dissipated excess pore pressure-induced settlement

Upon dynamic loading, saturated soils lose their strengths and undergo deformations resulting in volumetric-induced settlements that vary according to the excess pore pressure generation and dissipation variations. Traditionally, these settlements have been evaluated using standard charts based on one soil type and its relative density (RD). To assess these settlements, this study established a unique experimental methodology based on two laboratory testings: triaxial simple shear and piezoelectric ring actuator technique. Fifty-seven tests were performed on Ottawa F65 sand under strain-controlled cyclic and post-cyclic conditions. A chart was generated, revealing a relationship between the dissipated energy from cyclic loading and volumetric strain ( εv ), based on the shear wave velocity as a controlling factor. This study was compared with previous studies to verify the compatibility of the proposed approach. Another novelty was revealed by studying εv variation with the dissipated pressure. This variation is presented in a post-seismic chart in which deformations are tracked based on the initial soil state and maximum excess pore pressure generation ratio ( Rumax) at the end of the loading phase. For each RD, the soil is divided between liquefied and non-liquefied states according to a specific Rumax ( Rumax-trigger point). The calculation of the volume compressibility coefficient is proven to serve as a liquefaction-triggering criterion identifying the liquefied state.

Analytical solution for consolidation of saturated viscoelastic soils around tunnels with general Voigt model

This paper presents a novel analytical solution for the consolidation behavior of viscoelastic saturated soft soil subjected to large-scale ground loading. The rheological properties of clay are described using the general Voigt model. Based on the Terzaghi-Rendulic theory, the governing equations for the dissipation of excess pore water pressure in the surrounding soil mass of a tunnel are established under the first and second boundary conditions. The governing equations are solved using the complex variable method. The obtained solutions are verified by reducing them to the forms of three traditional rheological models, demonstrating the reliability of the proposed approach. Finally, based on the established solutions, the dissipation characteristics of excess pore water pressure around the tunnel are analyzed. The case results indicate that the soil permeability coefficient (k), the independent Newtonian viscosity coefficient (K0) and Hooke’s spring modulus (E0) in the general Voigt model have significant influences on the dissipation of excess pore water pressure and the degree of consolidation. A larger k, K0, and E0 lead to faster dissipation and consolidation development, while a greater tunnel buried depth (b) results in slower consolidation process. The influence of k on excess pore water pressure dissipation is more significant than that of K0 and E0. For the first boundary type, consolidation is instantaneous when k > 0.1 m/d. For the second type, when k < 0.0001 m/d, excess pore pressure remains unchanged within 100 d. The permeability condition of the tunnel has a considerable impact on the distribution of excess pore water pressure in the soil layer directly above the crown. When the tunnel is fully permeable, the effects of k, K0, and E0 on the dissipation of excess pore water pressure are more pronounced in the early stage, with almost complete dissipation of excess pore pressure above the tunnel before 100 d. However, when the tunnel is completely impermeable, their effects are more prominent in the later stage, and by 100 d, the maximum excess pore pressure within the depth range is 25 % of the initial.

Finite-difference solution for dissipation of excess pore water pressure within liquefied soil stabilized by stone columns with consideration of coupled radial-vertical seepage

The implementation of stone columns is a widely accepted method for improving the stability of liquefiable soil. A comprehensive understanding of the behavior of the composite ground is crucial for accurate design and calculation in practical applications. Several existing mathematical models were established to assess characteristics of the stone column-improved ground by typically ignoring the vertical seepage within liquefiable soil. This negligence will inevitably lead to significant calculation errors, particularly when the vertical permeability of liquefiable sites is high or the installation spacing of stone columns is large. In this context, a new mathematical model which accounts for coupled radial-vertical seepage within liquefiable soil is proposed to determine the reinforcement performance of stone columns. The equal strain assumption and new boundary conditions are incorporated to obtain numerical solutions with the finite difference method. Then the present solution is degenerated to the conventional calculation model to verify the reasonability of the proposed model. Finally, a parametric analysis is conducted to investigate the impacts of crucial parameters on the performance of stone columns for excess pore water pressure variation during soil liquefaction. The results reveal that the peak value of the maximum excess pore water pressure ratio increases with the increment of both the column spacing and cyclic stress ratio. Moreover, the increasing radial and vertical consolidation parameters Tb and Th will accelerate the dissipation rate of the excess pore water pressure of liquefiable sites. Furthermore, the conventional model neglecting the vertical seepage will underestimate the variation rate of the excess pore water pressure, and the calculation error will become larger with the increase of Th.