Disturbance failure mechanism of highly stressed rock in deep excavation:Current status and prospects

This article reviews the current status on the dynamic behavior of highly stressed rocks under disturbances.Firstly,the experimental apparatus,methods,and theories related to the disturbance dynamics of deep,high-stress rock are reviewed,followed by the introduction of scholars’research on deep rock deformation and failure from an energy perspective.Subsequently,with a backdrop of highstress phenomena in deep hard rock,such as rock bursts and core disking,we delve into the current state of research on rock microstructure analysis and residual stresses from the perspective of studying the energy storage mechanisms in rocks.Thereafter,the current state of research on the mechanical response and the energy dissipation of highly stressed rock formations is briefly retrospected.Finally,the insufficient aspects in the current research on the disturbance and failure mechanisms in deep,highly stressed rock formations are summarized,and prospects for future research are provided.This work provides new avenues for the research on the mechanical response and damage-fracture mechanisms of rocks under high-stress conditions.

Supplementation of vitamin E or a botanical extract as antioxidants to improve growth performance and health of growing pigs housed under thermoneutral or heat-stressed conditions

Background Heat stress has severe negative consequences on performance and health of pigs,leading to significant economic losses.The objective of this study was to investigate the effects of supplemental vitamin E and a botanical extract in feed or drinking water on growth performance,intestinal health,and oxidative and immune status in grow-ing pigs housed under heat stress conditions.Methods Duplicate experiments were conducted,each using 64 crossbred pigs with an initial body weight of 50.7±3.8 and 43.9±3.6 kg and age of 13-week and 12-week,respectively.Pigs(n=128)were housed individually and assigned within weight blocks and sex to a 2×4 factorial arrangement consisting of 2 environments(thermo-neutral(21.2℃)or heat-stressed(30.9℃))and 4 supplementation treatments(control diet;control+100 IU/L of D-α-tocopherol in water;control+200 IU/kg of DL-α-tocopheryl-acetate in feed;or control+400 mg/kg of a botanical extract in feed).Results Heat stress for 28 d reduced(P≤0.001)final body weight,average daily gain,and average daily feed intake(-7.4 kg,-26.7%,and-25.4%,respectively)but no effects of supplementation were detected(P>0.05).Serum vitamin E increased(P<0.001)with vitamin E supplementation in water and in feed(1.64 vs.3.59 and 1.64 vs.3.24),but not for the botanical extract(1.64 vs.1.67 mg/kg)and was greater when supplemented in water vs.feed(P=0.002).Liver vitamin E increased(P<0.001)with vitamin E supplementations in water(3.9 vs.31.8)and feed(3.9 vs.18.0),but not with the botanical extract(3.9 vs.4.9 mg/kg).Serum malondialdehyde was reduced with heat stress on d 2,but increased on d 28(interaction,P<0.001),and was greater(P<0.05)for antioxidant supplementation compared to control.Cellular proliferation was reduced(P=0.037)in the jejunum under heat stress,but increased in the ileum when vitamin E was supplemented in feed and water under heat stress(interaction,P=0.04).Tumor necrosis factor-αin jejunum and ileum mucosa decreased by heat stress(P<0.05)and was reduced by vitamin E sup-plementations under heat stress(interaction,P<0.001).Conclusions The addition of the antioxidants in feed or in drinking water did not alleviate the negative impact of heat stress on feed intake and growth rate of growing pigs.

Effects ofγ-aminobutyric Acid on Nitrogen Metabolism in Roots and Leaves of Cold-stressed Rice(Oryza sativa L.)During Early Vegetative Growth

Cold stress adversely affects rice growth,particularly at the early vegetative growth stage.In higher plants,nitrogen metabolism plays a central role in amino acid metabolism,plant defense mechanisms and productivity.This report investigated the effects of cold stress and supplementalγ-aminobutyric acid(GABA)under cold stress on nitrogen metabolism in rice seedlings.Cold stress resulted in a greater increase in the transformation to NH_(4)^(+)by nitrate reductase(NR)in roots,it further resulted in lower levels of NO_(3)^(-)content in roots,weakened glutamine glutamate(GOGAT/GS)pathway and elevated glutamate dehydrogenase(GDH)pathway of rice seedlings.Whereas,compared with cold stress,supplementation of GABA(2.5 mmol·L^(-1))could increase relative water content(79.43%)and biomass(34.15%)of rice seedlings.GABA could act as an amplifier of stress signal conduction/transduction to increase NR activity and promote NO_(3)^(-)assimilation in leaves.In addition,GABA elicited the Ca^(2+)signaling pathway which could promote the GDH pathway and GABA shunt,increase the activities of GS and GDH,and the expression of OsGAD2 and OsGDH family.The GABA might increase the ratio of the Glu family and avoid NH4+toxicity in order to raise the concentration of organic compounds and alleviate the harmful consequences of cold stress.Based on these observations,this study proposed that GABA mediated cold tolerance in rice seedlings by activating Ca^(2+)burst and subsequent crosstalk among Ca^(2+)signaling,GDH pathway and GABA shunt.

Stressed Coral Reef Identification Using Deep Learning CNN Techniques

Deep learning is a machine learning technique that allows the computer to process things that occur naturally to humans.Today,deep learning techniques are commonly used in computer vision to classify images and videos.As a result,for challenging computer vision problems,deep learning provides state of the art solutions to it.Coral reefs are an essential resource of the earth.A new study finds the planet has lost half of its coral reefs since 1950.It is necessary to restore and prevent damage to coral reefs as they play an important role in maintaining a balance in the marine ecosystem.This proposed work helps to prevent the corals from bleaching and restore them to a healthy condition by identifying the root cause of the threats.In the proposed work,using deep learning CNN techniques,the images are classified into Healthy and Stressed coral reefs.Stressed coral reefs are an intermediate state of coral reef between healthy and bleached coral reefs.The pre-trained models Resnet50 and Inception V3 are used in this study to classify the images.Also,a proposed CNN model is built and tested for the same.The results of Inception V3 and Resnet50 are improved to 70%and 55%by tuning the hypermeters such as dropouts and batch normalisation.Similarly,the proposed model is tuned as required and obtains a maximum of up to 90%accuracy.With large datasets,the optimum amount of neural networks and tuning it as required brings higher accuracy than other methods.

Antiplane shear crack in a prestressed elastic medium based on the couple stress theory

A prestressed elastic medium containing a mode-Ⅲcrack is studied by means of the couple stress theory(CST).Based on the CST under initial stresses,a governing differential equation along with a mixed boundary value problem is established.The singularities of the couple stress and force stress near the crack tips are analyzed through the asymptotic crack-tip fields resulting from the characteristic expansion method.To determine their intensity,a hypersingular integral equation is derived and numerically solved with the help of the Chebyshev polynomial.The obtained results show a strong size-dependence of the out-of-plane displacement on the crack and the couple stress intensity factor(CSIF)and the force stress intensity factor(FSIF)around the crack tips.The symmetric part of the shear stress has no singularity,and the skew-symmetric part related to the couple stress exhibits an r^(-3/2)singularity,in which r is the distance from the crack tip.The initial stresses also affect the crack tearing displacement and the CSIF and FSIF.

ACC and MACC Biosynthesis and Ethylene Production in Water-Stressed Spring Wheat

Changes of ACC and MACC levels, ACC synthase activity as well as ethylene production in the leaves of two spring wheat (Triticum aestivum L.) cultivars 8139 (with relatively low drought-resistance) and 504 (with relatively high drought-resistance) during water stress were determined. The levels of ACC and MACC in both cultivars decreased in the first 24 It of water stress and increased in the second 24 It while the activities of ACC synthase increased continuously throughout the entire period of treatment (48 h), As water stress progressed, ethylene production decreased continuously in cv. 8139 but remarkably increased earlier and decreased later in the cv. 504. Moreover, the decrease in RWC of stressed leaves was greater and the changes in ACC and MACC levels as well as ACC synthase activity were higher in the drought-sensitive cv. 8139 than in the drought-resistant cv, 504 during water stress. The levels of ACC and MACC, activities of ACC synthase and productions of ethylene in the stressed leaves in two cultivars were significantly altered by the application of MGBG (an inhibitor of SAMDC) and AOA (an inhibitor of ACC synthase) where their effects on these items were almost opposite. They were increased by the former inhibitor but reduced by the latter. All of these results suggested that the level of ethylene production in plants did not depend on the level of ACC during water stress. The increase in the level of ethylene in the drought-resistant cultivar during the earlier period of water stress might be a phenomenon of adaptation to water stress and be correlated with the development of the drought-tolerance in plants and playing role in the transduction of stress signal. The role of MACC, however, was primarily in the regulation of ethylene production under water stress.

Effects of Tremella Polysaccharide on Immune Function of Physically-Stressed Mice

An immunosuppressive animal model induced by physical stress that forced mice to swim in cold water(14±1℃)and the restorative effect of Tremella polysac charide(TP)on the suppressed immune function by stress were studied in mice.It was found that the spleen plaque forming cell(PFC)response to sheep red blood cells,delayed cuta- neous hypersensitivity(DCH)induced by dinitrochlorobenzene and the lymphocyte prolifer- ation stimulated by concanavalin A(Con A)were significantly decreased in stressed mice. In addition.the maximal decrease of PFC was reached in 9-12 days after stress.A- drenolectomy could not affect the decrease of PFC in stressed mice.TP(200.400mg/kg) ig for 8-14 days significantly restored the PFC.DCH and lymphocyte proliferation to nor- mal level in stressed mice.

Prestressed tensioning method and its application to testing anchor stress of anchor cables for side-slope stabilization

The anchor stress extent of a prestress anchor cable project has a direct relation with the project safety and performance. Prestressed tensioning method is a kind of nondestructive testing method, by which a reverse stretching load is applied on the external exposure section of anchor cable under construction or in service, and then the elongation variation of stress bars is measured to determine the anchor stress. We elaborated the theory and testing mechanism of prestressed tensioning method, and systematically studied key issues during the prestressed tensioning process of anchor cable by using physical model test, including the composition of tension stress-elongation curve, the variation of anchor stress, the compensation of locked anchor stress, and the judgment of anchor stress, and verified the theory feasibility of prestressed tensioning method. A case study on slope anchor cable of one highway project was conducted to further discuss on the test method, operation procedures and judgment of prestressed tensioning method on obtaining anchor stress, and then the test data of three situations were analyzed. The result provides a theoretical basis and technical base for the application of prestressed tensioning method to the evaluation of construction quality and operation conditions of anchor cable project.

Long-Term Bending Behaviour of Prestressed Glulam Bamboo-Wood Beam Based on Creep Effect

Creep is an important characteristic of bamboo and wood materials under long-term loading.This paper aims to study the long-term bending beha-viour of prestressed glulam bamboo-wood beam(GBWB).For this,14 pre-stressed GBWBs were selected and subjected to a long-term loading test for 60 days.Then,a comparative analysis was performed for the effects of pre-tension values,the number of pre-stressed wires,and long-term load on the stress variation of the steel wire and the long-term deflection of the beam midspan.The test results showed that with the number of prestressed wires increasing,the total stress of the steel wire in the beam midspan and the ratio of the long-term deflec-tion to the total deflection decreases decreased,but when the number of steel wires exceeded 4,the total stress and long-term deflection was less infuenced;with the pre-tension value increasing,the ratio of the total stress of the steel wire in the beam midspan and the ratio of the long-temm deflection to the total deflec-tion also decreased,but when the prestress force was greater than 3.975 kN,the:total stress and long-term deflection were less affected;with the other parameters unchanged,when the value of the long-term load increased,the total stress of the steel wire decreased,and the long-temm deflection of the beam midspan increased,which shall be more significant with the long-term load greater than 30%of the standard ultimate bearing capacity.After the test,the experimental data were fitted,and the creep coefficient was given.Finally,the long-term stiffness calcula-tion fommula of the pre-stressed GBWB based on creep effect was proposed.The research findings have certain theoretical significance and engineering value.

Cyclic load testing of pre-stressed rock anchors for slope stabilization

The objective of this research was to assess the characteristics of seismic induced damage and the deformation patterns of pre-stressed cement-grouted cables that are used for rock slope stabilization projects subjected to quasi-static cyclic loading.The experimental configuration includes the installation of 15 pre-stressed cables in a slope model made of concrete blocks(theoretically rigid rock mass) on top of a pre-existing sliding surface.The study showed that:(i) The pre-stressed cables exhibited great seismic performance.Rapid displacement of the model blocks was observed after the complete loss of the initial pre-stress load under continued applied cyclic loads and exceedance of the state of equilibrium,which implies the higher the initial pre-stress load,the better the seismic performance of the rock anchor;(ii) The failure of the pre-stressed cables was due to fracture at the connection of the tendons and cable heads under cyclic loading.The sequence of failure had a distinct pattern.Failure was first observed at the upper row of cables,which experienced the most severe damage,including the ejection of cable heads.No evidence of de-bonding was observed during the cyclic loading;(iii) The stress distribution of the bond length for pre-stressed cables was highly non-uniform.High stress concentrations were observed at both the fixed end and the free end of the bond length both before and immediately after the state of equilibrium is exceeded.The results obtained can be used to evaluate the overall performance of pre-stressed rock anchors subject to seismic loading and their potential as rockfall prevention and stabilization measures.

Methods for obtaining two way memory effect and stressed two way memory effect of CuAlNi single crystals

Various training methods for two way memory effect (TWME) and stressed two way memory effect (STWME) were tried on Cu 13.4Al 4.0Ni (mass fraction, %) single crystals by applying tensile stress along 〈001〉 direction of β phase. The training method of cooling with load can induce a lot of martensite prone to stabilize, thus cause large residual deformation, wide hysteresis and small TWME. Training with constant load can produce STWME larger than 8% with the least residual deformation. By training procedure of martensite reorientation below M f followed by thermal cycling, the TWME is relatively large with very small residual deformation and with comparatively narrow hysteresis of two way memory. The obtained two way memory curve after such training is not a closed loop, and the obtained TWME is not stable. However, these can be improved by thermal cycling. Training with martensite reorientation below M f and thermal cycling under relatively low constant stress throughout the whole training procedure is the optimum way of obtaining TWME, and more than 1.7% TWME can be obtained. The thermomechanical history of the sample has a pronounced effect on the training result. Thermomechanical cycling has a softening effect on martensite. [

Fatigue Damage Modeling for Partially Prestressed Concrete Beams under Repeated Loadings with Variable Amplitude

A full-range nonlinear analysis method for fatigue damage in prestressed concrete beams is presented. New damage accumulation models are proposed to describe the fatigue damage evolution in concrete and reinforcement respectively. Based on the stress analysis for cross section, the stress redistrbution in the fatigue damage process, due to the different damage mechanisms of concrete and reinforcement, is considered. The nonlinear damage analysis is achieved by means of piecewise linearity, and it is applicable on the condition of repeated loadings with variable amplitude. Fatigue damage modeling of a beam is implemented to illustrate that the proposed method can preferably fit the experimental results.

Fully Stressed Design of Fink Truss Using STAAD.Pro Software

This paper presents study of optimization of Fink Truss by Fully Stressed Design (FSD) method using STAAD.Pro software version STAAD.Pro V8i (SELECT series 5). Three spans of the trusses have been considered and each truss has been subjected to 27 types of load cases by changing nodal load locations. Central node load has been kept constant in each truss as 100 kN. Three sets of load condition is taken, viz, 100 kN, 120 kN and 150 kN. Total 81 trusses have been analyzed in this study to achieve a target stress of 100 MPa. Steel take-off for each case and maximum displacement for each case have been calculated and compared in this study and it shows that weight does not always increase with increase in the span or height. Results of the study could be helpful in designing a truss that does not waste material.

Web Shear Strengthening Technique of Deep Precast Prestressed Hollow Core Slabs under Truck Loads

Precast prestressed Hollow Core Slabs (HCS), are one of the famous and widely used slabs for concrete structures all over the world and widely implemented in the Middle East. HCS are used in industrial, commercial, residential buildings, as well as, in the parking structures. This paper succeeded to present new special details for deep HCS to enhance and strengthen the web shear strength capacity of HCS 400 and 500 mm depths respectively at the open parking area. This is subjected to heavy truck wheel loads so as to achieve the LRFD Code’s requirements. However, it is noticed many web shear cracks of HCS are used at parking area at many projects in Gulf Region. On the other hand, ACI318-14 permits no shear reinforcement in prestressed HCS thickness of less than 12.5 in (320 mm). The paper presents experimental tests program, to verify the numerical finite element of deep HCS under maximum design uniform loads, in addition to the new strengthening techniques. New strengthening techniques succeed to enhance the web shear capacity by significant percentage, due to the new details for HCS 400 by 68% up to 256% increasing of the web shear capacity compared to the ordinary HCS section. Also, HCS 500 shear capacity is enhanced with different percentages of strengthening techniques by 55%, up to 197% based on the different cases of strengthening. Furthermore enhancing deep HCS shear performance;the new techniques have an advantage of an easy execution at the site;casting with structural topping, otherwise the preparation can be done in precast factory before site handover, which saves time and cost compared to the others traditional strengthening techniques.

Stress Analysis of New Type Pre-Stressed Anchor Bearing Plate Combining Stamping with Welding Forming and Its Anchorage Zone

An anchor bearing plate transfers the anchoring force from anchor plate to the concrete and the pre-stress is formed in the concrete structure. Currently, the main type of anchor bearing plate is cast iron. It is brittle during transportation and tension process. This paper presents a new type of anchor bearing plate combined stamping with welding forming. The structure of the new type anchor bearing plate is introduced. The stress states of the anchor bearing plate and anchorage zone under work are studied. Various specifications of anchor bearing plate are studied by ANSYS finite element analysis software following the AASHTO specification. The analysis results are compared with the results of the same type of OVM round-shaped anchor plate. The study results show that the new pre-stressed anchor plates combined stamping with welding forming are feasible and more sturdy which can meet the engineering demand.

Comparative proteomic analysis of hippocampal proteins from chronic stressed rats

Chronic stress can induce hippocampus injury such as neuron loss and dendrite atrophy,but its mechanism and molecular basis remain unclear up to now.To understand the molecular mechanism on protein level and find the crucial proteins which correlated with chronic

REAL EFFECTS & DIVERSITY TO BE STRESSED IN INTERNATIONAL COOPERATION

In recent years, the Shanghai Institute of Organic Chemistry under the CAS has freed itself from the stereotyped rut of conventional forms in its external intercourse while still sticking fast to upholding its strategic goal of disciplinary development. Our stress in this aspect has shifted to the pursuit of real effects and diversified forms in international S&T exchange. Our exploration features the following four characteristics: