Evolution mechanism and treatment timing of penetrating fissures

The Inner Mongolia mining area in western China are characterized by the development of numerous penetrating fissures,resulting in severe land damage.It is significant to reveal the underlying evolution mechanism and identify treatment timing for restoring the ecological environment.The Guanbanwusu mining subsidence area in Inner Mongolia,China was selected as the research case for this study.The evolution mechanism of different penetrating fissures was revealed by field measurement,physical simulation and theoretical analysis.The treatment timing prediction model for the mining subsidence area was established based on the enhanced Weibull time function.The results show that the ground fissures are mainly step-type and collapse-type fissures.The breaking form of overlying strata determines their vertical opening and horizontal dislocation.The high mining intensity in the western mining area results in a shortened period of dynamic fissure expansion and reduced closure degree.The damage extent of the overlying strata exhibits zoning characteristics both vertically and horizontally.The relative standard deviation of the prediction model is only 3.7%.Concurrently,the prediction model is employed to determine the optimal timing for treatment in the study area,estimated to be 259 days.Subsequently,once this threshold is reached,the study area undergoes treatment and restoration of its e cological environment.This study addresses the knowledge gap in this field by highlighting the interconnectedness between rock strata structure and evolution mechanism of penetrating fissures,thereby providing a method for determining the treatment timing in mining subsidence areas.

Experimental study of the damage characteristics of rocks containing non-penetrating cracks under cyclic loading

The damage evolution process of non-penetrating cracks often causes some unexpected engineering disasters.Gypsum specimens containing non-penetrating crack(s)are used to study the damage evolution and characteristics under cyclic loading.The results show that under cyclic loading,the relationship between the number of non-penetrating crack(s)and the characteristic parameters(cyclic number,peak stress,peak strain,failure stress,and failure strain)of the pre-cracked specimens can be represented by a decreasing linear function.The damage evolution equation is fitted by calibrating the accumulative plastic strain for each cycle,and the damage constitutive equation is proposed by the concept of effective stress.Additionally,non-penetrating cracks are more likely to cause uneven stress distribution,damage accumulation,and local failure of specimen.The local failure can change the stress distribution and relieve the inhibition of non-penetrating crack extension and eventually cause a dramatic destruction of the specimen.Therefore,the evolution process caused by non-penetrating cracks can be regarded as one of the important reasons for inducing rockburst.These results are expected to improve the understanding of the process of spalling formation and rockburst and can be used to analyze the stability of rocks or rock structures.

Crack mechanism of ground fissures in loess layer of Fenwei Basin, China

The Fenwei Basin, covered by loess, experiences severe ground fissure disasters. These disasters disrupt the continuity of the loess and pose significant threats to engineering construction safety along transportation routes. Nevertheless, the crack characteristics and the influence zone of ground fissures in the loess layer remain inadequately investigated. To effectively prevent and control ground fissure disasters, physical model tests and the PFC(particle flow code) numerical simulation method are used to investigate the crack mechanism of buried ground fissures in the loess layer. The results show that there are two main cracks in the layer profile, which have a Y-shape morphology. As the dip angle of the preset cracks increased from 60° to 90°, the main deformation zone at the surface gradually shifted towards the footwall. The process of crack propagation from depth to surface is divided into five stages. Additionally, the results confirm the accuracy of the width of the rupture zone d2in the footwall calculated by the cantilever beam theory. These findings can offer theoretical guidance for determining the avoidance distance of ground fissures in loess regions, as well as for implementing disaster prevention and corresponding control measures for various stages of buried ground fissure propagation.

Heat transfer and temperature evolution in underground mininginduced overburden fracture and ground fissures: Optimal time window of UAV infrared monitoring

Heat transfer and temperature evolution in overburden fracture and ground fissures are one of the essential topics for the identification of ground fissures via unmanned aerial vehicle(UAV) infrared imager. In this study, discrete element software UDEC was employed to investigate the overburden fracture field under different mining conditions. Multiphysics software COMSOL were employed to investigate heat transfer and temperature evolution of overburden fracture and ground fissures under the influence of mining condition, fissure depth, fissure width, and month alternation. The UAV infrared field measurements also provided a calibration for numerical simulation. The results showed that for ground fissures connected to underground goaf(Fissure Ⅰ), the temperature difference increased with larger mining height and shallow buried depth. In addition, Fissure Ⅰ located in the boundary of the goaf have a greater temperature difference and is easier to be identified than fissures located above the mining goaf. For ground fissures having no connection to underground goaf(Fissure Ⅱ), the heat transfer is affected by the internal resistance of the overlying strata fracture when the depth of Fissure Ⅱ is greater than10 m, the temperature of Fissure Ⅱ gradually equals to the ground temperature as the fissures’ depth increases, and the fissures are difficult to be identified. The identification effect is most obvious for fissures larger than 16 cm under the same depth. In spring and summer, UAV infrared identification of mining fissures should be carried out during nighttime. This study provides the basis for the optimal time and season for the UAV infrared identification of different types of mining ground fissures.

Surface crack evolution patterns in freeze-thaw damage of fissured rock bodies

To explore the effects of freeze‒thaw cycles on the mechanical properties and crack evolution of fissured sandstone,biaxial compression experiments were carried out on sandstone subjected to freeze‒thaw cycles to characterize the changes in the physical and mechanical properties of fissured sandstone caused by freeze‒thaw cycles.The crack evolution and crack change process on the surface of the fissured sandstone were recorded and analysed in detail via digital image technology(DIC).Numerical simulation was used to reveal the expansion process and damage mode of fine-scale cracks under the action of freeze‒thaw cycles,and the simulation results were compared and analysed with the experimental data to verify the reliability of the numerical model.The results show that the mass loss,porosity,peak stress and elastic modulus all increase with increasing number of freeze‒thaw cycles.With an increase in the number of freeze‒thaw cycles,a substantial change in displacement occurs around the prefabricated cracks,and a stress concentration appears at the crack tip.As new cracks continue to sprout at the tips of the prefabricated cracks until the microcracks gradually penetrate into the main cracks,the displacement cloud becomes obviously discontinuous,and the contours of the displacement field in the crack fracture damage area simply intersect with the prefabricated cracks to form an obvious fracture.The damage patterns of the fractured sandstone after freeze‒thaw cycles clearly differ,forming a symmetrical"L"-shaped damage pattern at zero freeze‒thaw cycles,a symmetrical"V"-shaped damage pattern at 10 freeze‒thaw cycles,and a"V"-shaped damage pattern at 20 freeze‒thaw cycles.After 20 freeze‒thaw cycles,a"V"-shaped destruction pattern and"L"-shaped destruction pattern are formed;after 30 freeze‒thaw cycles,an"N"-shaped destruction pattern is formed.This shows that the failure mode of fractured sandstone gradually becomes more complicated with an increasing number of freeze‒thaw cycles.The effects of freeze‒thaw cycles on the direction and rate of crack propagation are revealed through a temperature‒load coupled model,which provides an important reference for an in-depth understanding of the freeze‒thaw failure mechanisms of fractured rock masses.

Performances of fissured red sandstone after thermal treatment with constant-amplitude and low-cycle impacts

In the engineering practices,it is increasingly common to encounter fractured rocks perturbed by temperatures and frequent dynamic loads.In this paper,the dynamic behaviors and fracture characteristics of red sandstone considering temperatures(25℃,200℃,400℃,600℃,and 800℃)and fissure angles(0°,30°,60°,and 90°)were evaluated under constant-amplitude and low-cycle(CALC)impacts actuated by a modified split Hopkinson pressure bar(SHPB)system.Subsequently,fracture morphology and second-order statistics within the grey-level co-occurrence matrix(GLCM)were examined using scanning electron microscopy(SEM).Meanwhile,the deep analysis and discussion of the mechanical response were conducted through the synchronous thermal analyzer(STA)test,numerical simulations,one-dimensional stress wave theory,and material structure.The multiple regression models between response variables and interactive effects of independent variables were established using the response surface method(RSM).The results demonstrate the fatigue strength and life diminish as temperatures rise and increase with increasing fissure angles,while the strain rate exhibits an inverse behavior.Furthermore,the peak stress intensification and strain rate softening observed during CALC impact exhibit greater prominence at increased fissure angles.The failure is dominated by tensile damage with concise evolution paths and intergranular cracks as well as the compressor-crushed zone which may affect the failure mode after 400℃.The second-order statistics of GLCM in SEM images exhibit a considerable dependence on the temperatures.Also,thermal damage dominated by thermal properties controls the material structure and wave impedance and eventually affects the incident wave intensity.The tensile wave reflected from the fissure surface is the inherent mechanism responsible for the angle effect exhibited by the fatigue strength and life.Ultimately,the peak stress intensification and strain rate softening during impact are determined by both the material structure and compaction governed by thermal damage and tensile wave.

Hydrogeochemical Characterization of Groundwater from Fissured Aquifers in the Angovia Mine Operating Permit Area (Central-West Côte d’Ivoire)

The main objective of this study is to determine the hydrogeochemical specificities of the groundwater of the Angovia mine operating permit, located in the Yaouré mountains in the center-west of Côte d’Ivoire. To do so, descriptive and multivariate statistical analysis methods with the SOM (Self Organizing Maps) algorithm were applied to the physicochemical parameters of 17 boreholes using the calcite (ISC) and dolomite (ISD) saturation indices. The results obtained have shown that the groundwater in the Angovia mine operating permit area has an average temperature of 27.52°C (long rainy season) and 27.87&degC (long dry season) and has an average pH of 7.09 ± 0.35 during the main rainy season and 7.32 ± 0.35 during the main dry season. They are mineralized with an average electrical conductivity of 505.98 ± 302.85 μS/cm during the long rainy season and with 450.33 ± 233.74 μS/cm as average during the long dry season. The main phenomena at the origin of groundwater mineralization are water residence time, oxidation-reduction and surface inflow. The study of the relative age of the water shows that the groundwater in the Angovia mine operating permit area is mainly undersaturated with respect to calcite and dolomite. They are therefore very old in the aquifer with a slow circulation speed during the long rainy season and the long dry season.

Anal pruritus:Don’t look away

Anal pruritus is a common anorectal symptom that can significantly impair a patient’s quality of life,including their mental health.It can be one of the most difficult proctological conditions to treat.Patients often delay seeking medical attention,since it is an embarrassing but non-life-threatening situation.Pruritus ani can be associated with idiopathic and secondary causes,such as anorectal diseases,cancer(anal or colorectal),dermatological and sexually transmitted diseases,fungal infections and systemic diseases.If patients are referred for a colonoscopy,this can sometimes provide the first opportunity to evaluate the perianal area.Classifications of anal pruritus are based on the abnormalities of the perianal skin,one of the most commonly used being the Washington classi-fication.A proper digital anorectal examination is important,as well as an anoscopy to help to exclude anorectal diseases or suspicious masses.Endoscopists should be aware of the common etiologies,and classification of the perianal area abnormalities should be provided in the colonoscopy report.Information on treatment possibilities and follow-up can also be provided.The treatment normally consists of a triple approach:proper hygiene,elimination of irritants,and skin care and protection.Several topical therapies have been described as possible treatments,including steroids,capsaicin,tacrolimus and methylene blue intradermal injections.

Anal Pathologies: What Management at the Reference Health Center of Bamako’s Commune V?

Anal pathologies are conditions affecting the anal margin and the anal canal. The aim of our study was to update data on anal diseases. Non-specific, it can reveal an emergency, a serious illness, a chronic disease or a benign condition. It was a prospective, descriptive and analytical study from April 2022 to March 2023, carried out in the hepato-gastroenterology unit of the Centre de Santé de Référence de la commune V du District de Bamako in Mali. Out of seven hundred and forty-nine (749) patients seen in consultation, 98 had anal pathology, i.e. a prevalence of 13.08%. The mean age was 40 ± 15.15 years and the sex ratio was 1.5. Hemorrhoidal disease and anal fissure were the most frequent pathologies in 66.4% and 24.4% of cases respectively. Medical treatment was initiated in 91.9% of patients with hemorrhoidal disease and 91.7% with anal fissure. Anal pathologies are common in young male patients. In our context, they are dominated by benign conditions.

Liver surface depressions in the presence of diaphragmatic muscular bands on trans-illumination

Traditional descriptions of liver anatomy refer to a smooth,convex surface contacting the diaphragm.Surface depressions are recognized anatomic variants.There are many theories to explain the cause of the depressions.We discuss the theory that these are caused by hypertrophic muscular bands in the diaphragm.

Effect of Application of One-Time Method and Multiple Root Canals on Cryptic Fracture with Endodontic Lesions and VAS Score

Objective:To evaluate the therapeutic efficacy of primary method root canal treatment(ORCT)and multiple root canal treatment(MRCT)for dental cryptocleidosis with endodontic lesions.Methods:88 patients with fissured teeth with endodontic lesions who were admitted to the hospital between November 2021 and November 2023 were selected,and after randomized numerical table grouping,44 cases in the experimental group were included in the ORCT treatment,and 44 cases in the reference group were included in the MRCT treatment,and the total effective rate,root canal filling rate,visual analog scale(VAS)score,periodontal indexes,and the complication rate were compared.Results:The total effective rate and root canal filling rate of the experimental group were higher than that of the reference group;after treatment,the VAS score of the experimental group was lower than that of the reference group,and the periodontal indexes were lower than that of the reference group;and the complication rate of the experimental group was lower than that of the reference group(P<0.05).Conclusion:ORCT can improve the overall efficacy of patients with fissured teeth with endodontic lesions,ensure the filling rate of root canals,significantly reduce pain symptoms,improve a number of periodontal indicators,have high endodontic safety,and have more therapeutic advantages than MRCT.

Research on the feasibility of storage and estimation model of storage capacity of CO_(2)in fissures of coal mine old goaf

The concept of the carbon cycle in the old goaf of a coal mine based on CO_(2)utilization and storage was put forward adhering to the principle of low-carbon development,utilization of space resources in old goafs,and associated gas resources development.Firstly,the evolution characteristics of overburden fissures in the goaf of the case was studied using a two-dimensional physical similarity simulation test,the sealing performance of the caprocks after stabilization was analyzed,and the fissures were counted and classi-fied.Then,the process of gaseous CO_(2)injection in the connected fissure was simulated by Ansys Fluent software,and the migration law and distribution characteristics of CO_(2)under the condition of gaseous CO_(2)injection were analyzed.Finally,the estimation models of free CO_(2)storage capacity in the old goaf were constructed considering the proportion of connected fissure and the effectiveness of CO_(2)injection.The CO_(2)storage capacity in the old goaf of the case coal mine was estimated.The results showed that a caprock group of“hard-thickness low-permeability hard-thickness”was formed after the caprock-fissures system in the goaf of the case tended to be stable vertically.The connected fissure,occlude cracks,and micro-fractures in the goaf accounted for 85.5%,8.5%,and 6%of the total fissures,respectively.Gaseous CO_(2)first migrated to the bottom of the connected fissure after CO_(2)was injected into the goaf,then spread horizontally along the bottom of the connected fissure after reaching the bottom,and finally spread longitudinally after filling the bottom of the entire connected fissure.The theoretical and effective storage capacities of free CO_(2)at normal temperature and pressure in the old goaf of the case were 9757 and 7477 t,respectively.The effective storage capacity of free CO_(2)at normal temperature and pressure in the old goaf after all minefield mined was 193404 t.The research can provide some reference for the coal mining industry to help the goal of“carbon peaking and carbon neutrality”.

Automated identification of fissure trace in mining roadway via deep learning

The fractured rocks distributed near the structural surface of coal roadway heading face can easily cause water or air conduits,ultimately resulting in accidents that threaten production safety,such as mine flooding,gas leakage,or supporting failure.Therefore,successful detection of fissures is crucial to mine safety.Despite the rising popularity of computer vision in accurate fissures detection,it fails to satisfy the demand of engineering practice.To address this problem,this paper first establishes a 1000-image database of fissures of coal roadway heading face based on data collection,cleaning,and annotation.Then,a framework for fissure detection and segmentation is constructed with deep convolutional neural network(DCNN)named DeepLabv3+ serving as the overall architecture,and a lightweight MobileNetV2,instead of the original Xception,as the main feature extraction network.The database is then employed to train and test the neural network model.Finally,the robustness and adaptability of the model under the common jamming environment in coal mines are evaluated.According to the results,the deep learning algorithm,which performs favorably in identifying various fissures in the coal roadway heading face,is immune to interference such as low illumination,wire mesh,multi-scale edge,cutting mark,and concentrated light beams.Notably,the performance of such method is on par with,or better than,humans in performing individual image segmentation.The approach performs higher segmentation accuracy and calculation speed than the traditional image identification algorithm,thus realizing rapid identification of fissures in coal mines in batch.This study can provide a reference for image semantic segmentation of fissure traces under similar conditions.

Ground fissure development regularity and formation mechanism of shallow buried coal seam mining with Karst landform in Jiaozi coal mine: a case study

A comprehensive study was undertaken at Jiaozi coal mine to investigate the development regularity of ground fissures in shallow buried coal seam mining with Karst landform,shedding light on the development type,geographical distribution,dynamic development process,and failure mechanism of these ground fissures by employing field monitoring,numerical simulation,and theoretical analysis.The findings demonstrate that ground fissure development has an obvious feature of subregion,and its geographical distribution is significantly affected by topography.Tensile type,open type,and stepped type are three different categories of ground fissure.Ground fissures emerge dynamically as the panel advances,and they typically develop with a distance of less than periodic weighting step distance in advance of panel advancing position.Ground fissures present the dynamic development feature,temporary fissure has the ability of self-healing.The dynamic development process of ground fissure with closed-distance coal seam repeated mining is expounded,and the development scale is a dynamic development stage of“closure→expansion→stabilized”on the basis of the original development scale.From the perspective of topsoil deformation,the computation model considering two points movement vectors towards two directions of the gob and the ground surface is established,the development criterion considering the critical deformation value of topsoil is obtained.The mechanical model of hinged structure of inclined body is proposed to clarify the ground fissure development,and the interaction between slope activity and ground fissure development is expounded.These research results fulfill the gap of ground fissures about development regularity and formation mechanism,and can contribute to ground fissure prevention and treatment with Karst landform.

Microtremor-based analysis of the dynamic response characteristics of a site containing grouped earth fissures

In this study,the Beibu earth fissure site in the northeastern part of Weihe Basin,which contains four nearly parallel earth fissures,was studied.A long straight microtremor measuring line,containing 49 measuring points across four earth fissures,was established to investigate the dynamic response of this site using Fourier spectrum,response acceleration spectrum,Arias intensity,and HVSR analyses.The main results are as follows:(1)The fundamental frequencies of 44 measuring points obtained from HVSR analysis are concentrated within 1.67 Hz-2.25 Hz,and the existence of the earth fissures has little effect on the fundamental frequency changes.(2)There is an amplification effect near a single earth fissure.The dynamic responses are large at the measuring points near the earth fissure,and the values decrease with increasing distance from the earth fissure.In areas between two adjacent earth fissures,these values decrease and are even lower than those in sites without amplification effects.(3)In this earth fissure site,the general area(or less affected area)and affected areas were delineated based on the amplification effect.In engineering applications,construction design should avoid these affected areas and existing structures should be reinforced to satisfy the seismic fortification requirements.

Evaluation of the Efficacy of 99.9% Pure Silver Trilaminate Cups in the Prevention and Treatment of Nipple Pain and Fissures

Breastfeeding is drastically decreasing over time and nipple trauma constitutes one of the most significant reasons for its discontinuation. In this context, this study aimed at evaluating the effectiveness and tolerability of a topical treatment device, namely Silver Cap® (Depofarma S.P.A.), when used to prevent pain and nipple fissure formation. The medical device consists in a silver trilaminate cup to be placed on the nipple, providing physical protection and creating a moist environment. The study involved 187 women: 38 started to apply the device prior to lactation (PL group) and 149 during lactation (DL group). Aiming to collect safety and performance data, both groups were provided with questionnaires during 6 consecutive visits (120 days of follow-up). At last visit, absence of painful symptoms was reported by the 98.8% and the 100% of women in DL and PL groups, respectively. Moreover, no nipple fissures were observed and no adverse events directly correlated to use of the device were reported. According to these findings, it can be concluded that Silver Cap® is a safe and effective device for nipple pain and fissure prevention. .

Comparative analysis of Parikartika and Anal Fissure: unraveling diagnostic, therapeutic, and surgical dimensions

Background:Agnimandya,the underlying cause of anorectal disorders,of which Parikartika is the most well-known,is brought on by lifestyles characterized by sedentary behavior,elevated stress,poor nutrition,and sleep habits.The illness known as Parikartika,with signs and symptoms like fissure-in-ano in modern sources,is characterized by kartanvat Vedana(cutting pain)over the anal region.Acute fissure-in-ano is treated with analgesics,stool softeners,and soothing creams.Treatment options for hazy chronic fissures include anal dilatation,sphincterotomy,fissurectomy,and anal advancement flap.In addition to using laxatives and substances that promote wound healing(vranaropaka),the concepts of management of Parikartika in Ayurveda are more heavily weighted towards enhancing the nature,character,and consistency of stool and stabilizing the digestive functions Parikartika is mentioned in Ayurvedic texts as a complication of many Ayurvedic procedures,such as Vamana,Virechana,and Basti,as well as a complication of some disorders,such as Arsh,Atisar,and Grahani.Aim and objective:This article aims to comprehensively review the literature,diagnostic,and therapeutic aspects of Parikartika,with its correlation to Fissure in ano,and compare the clinical outcomes of the treatment modalities with supporting references,consolidating all pertinent information on the subject.Material&method:Collection from Samhita’s,commentaries,exploring medical websites,Ayurvedic journals related to the topic of Parikartika and fissure in ano,systematic record of the collected literature and a summary of each item.Organize the collected materials,reference and citation are the material and method followed here.Discussion&conclusion:This is an extensive literature review on Parikartika in Ayurveda,exploring its contemporary association with Fissure in Ano.The research offers insights that can inform the evaluation and treatment of this condition,considering both conservative and surgical approaches,thereby enhancing clinical management strategies.

Pre-Rupture Aneurysm of the Juxta and Sub-Renal Abdominal Aorta in Early Pregnancy: A Case Report

Aneurysm of the abdominal aorta is the result of a weakening of the arterial wall and corresponds to abnormal dilatations of the arteries defined as an increase ≥ 50% of the arterial diameter compared to the normal segments. A long asymptomatic, abdominal aortic aneurysm can be a catastrophic maternal-fetal situation due to the high risk of rupture induced by pregnancy. A rare association between aneurysm and pregnancy poses a problem of diagnosis and standardized management. The lack of knowledge of this condition regularly leads to a delay in management, which is a source of excess mortality. We report the case of a patient with a progressive pregnancy of 12 weeks of amenorrhea who presented with a large sub renal abdominal aortic aneurysm with thrombosis and fissuring in order to discuss the diagnostic and management aspects of this association.

A review on investigation of water-preserved coal mining in western China

Yushenfu mining area is located in an ecological fragile area in western China, the coal seam of which is the Jurassic Ysn'an Foirnalion. The Jurassic Yan'an Formation con tains five minable coal seams, the top layer of which is thick, covered by shallow overburden and located under aquifers. Therefore, the mining induced water flowing fractured zone can easily extend to the aquifers of both the Quaternary Sarahu and Jurassic Zhiluo Formation. This would result in a series of negative hydrological and ecological effects, including groundwater leakage, groundwater lowering, furtherly causing surface vegetation withering and dying, surface water body reduction, spring drying out, and water flow of river being decreased substantially. To solve these environmental problems, several technologies have been carried out by Chinese scientists, one of which is water-preserved coal mining. This paper presents a review of the origin, definition and development of water-preserved coal mining, and its applications in Yushenfu mining area. The applicable conditions, research contents, research methodology, and technical foundation of water-preserved coal mining are addressed in this paper. The future research focuses regarding water-preserved coal mining in China are also discussed in this paper. Its results serve as a guide for selecting the methods to be preferred for mining in case the geological conditions, roof overburden structure and coal mining process are similar to Yushenfu mining area.

Fracture evolution characteristics of sandstone containing double fissures and a single circular hole under uniaxial compression

The uniaxial compression experiments on the sandstone samples containing double fissures and a single circular hole were carried out by using electro-hydraulic servo universal testing machine to investigate the effect of rock bridge angle β and fissure angle α on mechanical properties and evolution characteristics of cracks.The results show that the peak strength,peak strain and elastic modulus of defected specimens decrease comparing with those for intact sample,and show a decreased trend firstly and then increase with β changing from 0° to 90°.The peak strength and elastic modulus achieve the minimum value as the rock bridge angle is 60°,while the peak strain reaches the minimum value with the rock bridge angle of 45°.The crack initiation of tested rock samples occurs firstly in stress concentration areas at tips of prefabricated fissures under uniaxial compression,and then propagates constantly and coalescences with the prefabricated hole.Some secondary cracks initiate and propagate as well until buckling failure happens.The rock bridge angle has a great influence on crack initiation,coalescence,final failure mode,crack initiation stress and transfixion stress.The peak strength varies significantly,while the elastic modulus and peak strain change slightly,and the failure modes are also different due to the influence of fissure angle.