Stress Relief Measurements in Young Adults and Adolescents—A Comparative Pilot Study with Different Relaxation Programs

Background: Chronic stress is a emotional challenge. Constant pressure presents a serious risk of damage to mental and physical health and hence is associated with increased incidence of various diseases. The ability to cope with chronic stress may be a function of psychological resilience including intellectual capacities, but more so of external factors such as life experience and education. Adolescents are more vulnerable to chronic stress than adults. The measures introduced during the COVID-19 pandemic brought up major societal problems. As both children and adolescents lost their life anchors, the prevalence of stress in adolescents increased from 20% to 45%. Chronic psychological stress can impede the normal development of schoolchildren. It may cause anxiety, social withdrawal, interpersonal conflicts and aggression. This applies particularly to those in puberty, with the adolescent already facing unstable social bonds and elevated fear about the future. It is likely that the puberty cohort accounts for the dramatic increase in the prevalence of stress. Since it impacts public health, chronic stress among school-age children is increasingly taking on a socio-political dimension. Non-clinical stress intervention studies can investigate how to achieve stress reduction in school children. Methods: In a small pilot study, we analysed the effects of a training program with four different standard interventions, i.e. mindfulness training, progressive muscle reflection, autogenic training, and sound meditation. We obtained baseline scores of 10 stress-indicators, and re-tested after the interventions were performed. Results: The four applied interventions resulted in a reduction of 8 (out of 10) stress-indicators, such as “feeling stressed” or stress related symptoms (headaches, dizziness, sweating). This positive impact of the interventions significantly reduced “Fears about the future” (p Discussion: School children recognise the positive potential of stress reducing training or interventions. Our results provide evidence in support of integrating the training of relaxation techniques in the school curriculum. We propose that a larger study be undertaken to determine which methods would be most effective.

SIMULATION OF VIBRATION STRESS RELIEF AFTER WELDING BASED ON FEM

A finite element model is developed for the simulation of vibration stress relief （VSR） after welding. For the nonresonant vibration, the reduction in stress strongly depends on the amplitude of vibration. For the resonant vibration, the vibration frequency is the key for stress relief. The vibration frequency should be close to the structure natural frequency for the desired vibration mode. Only small vibration amplitude is required, which will be amplified during vibration. Vibration time does not have a major impact on vibration stress relief. When the amplitude of vibration stress relief is large, the treatment will be more effective.

Non-complete relief method for measuring surface stresses in surrounding rocks

The measurement of surface stresses in surrounding rocks with the use of a relief method of annular hole-drilling was studied by numerical analysis. The stress relief process by hole-drilling was then simulated with the use of finite element method. The influences of the borehole diameter(d), the initial stresses and the ratio of the initial principle stresses on the variations of the remained stress and the released stress in function of the relief depth(h) were discussed. The relation between the non-dimensional ratio of the released principle strains and that of the initial principle stresses, and the effect of the elastic modulus and the Poisson ratio of the rock mass on the stress relief curves were studied. The results show that the stress relief behavior formulated with the non-dimensional ratio of the released stress and the ratio of h/d is only sensitive to the ratio of the initial principle stresses and the Poisson ratio. The stresses are completely released when h equals 1.6d, and the tensile stresses take place on the bore core surface in the relief measurement process. Finally, a non-complete relief method of annular hole-drilling for measuring surface stress in surrounding rocks is proposed and the procedure is presented.

Evaluation of residual stress relief of aluminum alloy 7050 by using crack compliance method

High strength aluminum alloys of 7xxx series have unacceptable levels of quenching residual stresses from solution heat treatment. The residual stress not only results in machining distortion and dimensional instability, but also increases the possibility of stress corrosion cracks. Therefore, it is necessary to reduce the residual stress to an acceptable level. The crack compliance method was adopted to study the influences of various stress relief methods on residual stress patterns in 7050 aluminum alloy. The results show that 90% residual stress can be eliminated by the cold stretching(Tx51) method. And a lower level of residual stress can be achieved by the uphill quenching(Tx53) method or the cold compression(Tx52). However, there is a very steep residual stress gradient normal to exterior surfaces.

TECHNOLOGY OF QUANTITATIVE ANALYSIS ON VIBRATORY STRESS RELIEF BASED ON ULTRASONIC TIME-OF-ARRIVAL METHOD

The effect of vibratory stress relief （VSR） is usually evaluated with the indirect method of observing the change of amplitude frequency response characteristics of structures. A new kind of evaluating method of VSR based on the ultrasonic time-of-arrival method （UTM）, which can obtain the residual stress directly through measuring the propagation time of ultrasonic wave in the material, is presented. At first, the principle of the measuring method of residual stress based on UTM is analyzed. Then the measuring system of the method is described, which is in virtue of ultrasonic flaw detector and high-sampling-rate digital oscillograph. And a set of calibration system that contains a piece of standard specimen is also introduced. Experimental results prove the relation between the residual stress and the propagation time of ultrasonic in workpieces. Finally, the measuring and calibration systems are applied in evaluating the effect of VSR. The final test results show that the method is effective.

A Numerical Investigation of the Stress Relief Zones Around a Longwall Face in the Lower Seam for Gas Drainage Considerations

Extraction of a protective coal seam (PVCS)-below or above a coal seam to be mined with the potential of coal andgas outburst risk-plays an important role not only in decreasing the stress field in the surrounding rock mass but alsoin increasing the gas desorption capacity and gas flow permeability in the protected coal seam (PTCS). The PVCSis mined to guarantee the safe mining of the PTCS. This study has numerically evaluated the stress redistributioneffects using FLAC3D model for a longwall face in Shanxi Province. The effects of mining depth, mining height andinter-burden rock mass properties were evaluated using the stress relief angle and stress relief coefficient. Verticalstress distribution, stress relief angle and stress relief coefficient in the PTCS were analyzed as the face advancedin the PVCS. The results showed that the stress relief achieved in different locations of the PTCS varied as the faceadvanced. Sensitivity analyses on the pertinent variables indicate that the stress relief in the PTCS is affected mostby the mining depth followed by the inter-burden lithology and the mining height. Furthermore, the elastic moduliof different layers within the inter-burden rock mass are more important than their uniaxial compressive strength(UCS) and Poisson’s ratio. These observations can guide gas drainage borehole design to minimize the accidentsof coal and gas outbursts.

Influence of Cultural Alienation on Happiness of Overseas Students: Mediating Role of Stress Relief and Regulating Role of Cultural Intelligence

When the global outbreak of new coronary pneumonia broke out in 2020,online public opinion events triggered by cultural differences among overseas students had come into the public view.To further explore the relationship between the cultural alienation of overseas students and their own happiness,this study takes visualization and analysis of positive,negative sentiment analysis of Weibo netizens’comment data in the“Xu Kexin Incident”as the starting point,on the basis of introducing cultural alienation,stress relief methods,and cultural intelligence,combining gender and social ability,social relations and other individual attributes,designed a questionnaire to investigate 502 overseas students,through the construction and analysis of the adjusted Cox risk ratio intermedi-ary model,comprehensive single factor interference and multi-factor cross-over comprehensive analysis.The results show that the cultural alienation of overseas students has a significant effect on their own well-being.The study concluded as follows:(1)Netizens hold polarized views on the three dimensions of overseas students’mask,safety,and culture;(2)Stress relief methods play an intermediary role between cultural alienation and the happiness of overseas students,among which Negative stress relief methods play a greater role;(3)The level of cultural intelligence regulates the intermediary process of stress relief methods.The higher the level of cultural intelligence,the stronger the regulatory effect.

某跨声速风洞用980 高强度钢的去应力热处理工艺研究

热处理是结构件制造的重要环节,与结构件的制造质量和使用性能紧密相关。对某型号跨声速风洞用980高强度钢去应力热处理工艺进行了研究,采用拉伸试验和-20℃低温冲击试验,对比分析了一次、二次去应力退火试验后980高强度钢的强度和韧性。结果表明,当去应力热处理工艺为去应力退火温度为(450±10)℃,保温时间为10~12 h时,跨声速风洞用980高强度钢材料可获得最优的强度和韧性。试验结果对同类材料的去应力热处理具有一定的借鉴意义。

基于隧道施工阶段地应力实测数据的岩爆判据研究

云南省蔓金高速草果山隧道属于深埋长隧道,隧道围岩坚硬完整且脆性较高,隧道施工阶段面临着岩爆发生的风险。因此,采用应力解除法进行地应力测量,并基于实测数据结合现场岩爆发生情况与国内外不同的强度判据进行对比,并对岩爆判据的适用性进行分析研究。最后,根据岩爆实际发生的情况和位置对岩爆判据进行验证分析,结果表明:岩爆预测标准除应力指标外,还应使用多因素指标进行综合判别;某种岩爆预测方法不能适用所有地下工程,应结合工程的具体情况,进行岩爆危险性评估,为工程提出岩爆防治措施。同时此研究成果为深埋完整硬岩的岩爆灾害分析预测和防控提供了参考依据。

首山一矿深部地应力分布规律及影响因素

为探讨平顶山首山一矿深部地应力分布规律及其影响因素,基于矿井实测地应力数据,运用构造物理学、岩石力学和数值模拟方法,研究了测点地应力类型、大小和方向分布规律,反演了地应力场分布特征,分析了埋深、岩性和地质构造对地应力的影响,确定了影响地应力分布的主控因素。研究表明:多元回归反演分析法获得的地应力计算值与实测值吻合,相对误差小于20%,结果可靠。矿井煤岩体处于三维压应力状态,煤层主应力关系为S_(H)>S_(V)>S_(h),地应力由矿井北部向南部呈现先增大后减小再增大的变化趋势,地应力为28~44 MPa,属于高应力水平,地应力方向为NEE向。埋深影响地应力大小和类型,随埋深增加主应力增大,应力场类型向准静水压力场过渡;岩性与地应力密切相关,从泥岩到砂岩或灰岩,地应力增大,弹性模量越大地应力越大,地层岩性的差异造成地应力大小离散分布、应力方向偏转角不超过10°;矿井地应力与埋深、弹性模量的关系可表示为σ_(H)=0.0350H+0.4681E−8.5513。地质构造是影响首山一矿地应力分布的主控因素,褶皱形态控制地应力的水平应力分布,向斜内弧应力值大于背斜内弧,且褶皱弯曲程度越大,其内弧地应力越大,应力梯度越大;断层带内应力降低、断层尖灭端应力集中,地应力方向沿着断层走向偏转,与断层走向夹角越大,应力方向偏转角越大;断层切割复式褶皱时,断层与向斜构造组合区应力值大于断层与背斜构造组合区,且断褶构造组合造成地应力方向分布紊乱。

松软煤层底板爆破致裂增透模拟试验研究及应用

针对松软煤层爆破增透钻孔施工困难,爆破增透产生的裂隙不发育且易于重新压实的问题,提出在底板岩层开展爆破作业,达到松软煤层增透进而增加瓦斯有效抽采时间的目的。为了监测跨界面应力波传播规律及煤层损伤状况,在实验室构建了物理模型并开展了煤层底板爆破相似模拟试验。同时使用数值模拟的研究方法对煤层底板爆破过程中煤、岩体内部的损伤及裂隙的演化过程进行补充。结果表明:松软煤层底板爆破裂纹沿爆破孔向四周岩体扩展,爆破孔位置和底板煤岩交界面以及煤层内部的破坏较为严重,产生跨界面损伤裂纹。爆炸应力波从松软煤层底板岩层传播到松软煤层时,岩体和松软煤体的交界面产生透射压缩应力波和反射拉伸应力波,透射波作用于松软煤体,使煤层裂隙增加;反射波反作用于岩体,在煤岩交界面形成交叉裂纹,使底板岩层裂隙和松软煤层裂隙贯通,有利于松软煤层的瓦斯垂向运移流动和卸压瓦斯抽采。潘一东煤矿现场应用表明,煤层底板爆破增透后瓦斯抽采纯量及其浓度快速上升,抽采纯量从0.06 m^(3)/min提高到1.46 m^(3)/min,增加了23.33倍;瓦斯浓度从爆破前的10.46%上升到45.50%左右,增加了3.34倍,并且长时间维持在较高水平。研究成果可为深部松软煤层瓦斯高效抽采提供理论基础和技术支持。

底板动压巷道压裂弱结构体应力转移控制技术

为了满足煤矿安全生产的需要,许多巷道都会布置在煤层底板中,如部分运输大巷、排水巷道、瓦斯抽采巷道等。采动应力容易造成底板巷道围岩应力升高,加剧底板巷道围岩变形,造成支护永久失效、顶板下沉、巷道底鼓、两帮收敛等破坏。针对此,提出了在应力传递路径上实施水力压裂,在指定的区域制造出一定空间形态的水压裂缝网,形成压裂弱结构体,实现区域范围内的应力转移,从而降低巷道区域范围内的应力,控制巷道的围岩稳定性的控制技术,并通过理论分析及现场工程验证等方式,揭示了底板动压巷道压裂弱结构体应力转移的力学机制,建立了相应的力学模型,对压裂弱结构体的合理位置、范围等影响因素进行了求解。得出:(1)压裂弱结构体使局部应力场发生明显变化,出现应力升高区和应力降低区,应力降低区主要分布在弱结构体与采动应力连线的方向上,主要集中在一个拱形的范围内;由于膨胀效应,在与应力来源垂直的方向上产生应力集中,出现应力升高区。(2)最大主应力变化幅度与压裂弱结构体的长轴长L、短轴长H、到巷道的距离P、与巷道连线的水平夹角β、压裂层的强度C及内摩擦角α、压裂的损伤变量D等有关。其中到巷道的距离P对卸压效果影响最大,损伤变量D对卸压效果影响最小。(3)采用提出的计算方法设计了淮北矿业集团袁店一矿的103运输集中巷的卸压方案,工程应用结果表明,底板动压巷道变形速率明显减缓,验证了底板强动压巷道压裂弱结构体应力转移模型的合理性。

飞机结构梁多轴铣削加工程序与工艺优化研究

为解决飞机结构梁铣削加工过程中容易产生变形的问题。针对飞机结构梁类的薄壁腔体难加工零件进行了加工工艺分析和流程设计,此类零件的毛坯残余应力是影响零件加工变形的重要因素,有效的应力释放可以提高零件的加工质量。对此利用UGNX软件进行了数控编程,并利用VERICUT软件进行仿真,以最大切削厚度为目标进行了切削参数优化,优化后的程序能够有效的提高加工效率,并且探讨了以保证加工质量目标的刀轨编程策略和方法,有效的解决了飞机结构梁铣削加工过程中产生变形的问题。

复杂地质高应力条件下回采工作面冲击地压防治技术研究

针对济宁三号煤矿163下06工作面已探明正断层32条,逆断层1条,回采期间揭露隐伏断层11条,局部过联络巷、探巷不规则回采,不规则煤柱留设,局部煤体分割严重等,地质和开采技术条件复杂,应力集中程度高,冲击危险程度高;文章提出了,划分冲击危险区域、加强支护、宏观矿压动态观测、钻屑检测、应力在线监测,微震监测;大直径钻孔卸压、坚硬顶板深孔预裂等冲击地压综合监测防治措施,结果表明可以有效降低局部地应力异常集中,释放积聚的弹性能,取得了良好效果,确保了该工作面安全高效回采。

沿空留巷密集钻孔切顶机理及关键参数确定方法

为实现密集钻孔切顶条件下沿空留巷顶板结构安全稳定,研究正常情况与密集钻孔条件下顶板岩层结构受力状况,基于岩石断裂理论和弹性理论分析回采前后顶板密集钻孔孔间围岩受力分布及其破断过程,明确密集钻孔切顶机理及相邻钻孔的孔间集中应力相互作用机制,推导工作面端头弧形三角板结构巷道侧边界密集钻孔孔间围岩的拉剪应力计算公式。在此基础上,分析不同参数对孔间围岩所受拉剪应力的影响作用,提出沿空留巷密集钻孔切顶关键参数确定方法。研究表明:密集钻孔主要通过回采前后钻孔周围应力条件改变来增加钻孔围岩拉剪应力集中程度,引起孔间裂隙扩张联通,形成切缝线破断关键岩层。回采前钻孔主要受水平挤压应力影响,回采后钻孔受力逐渐转变为采空区顶板回转下沉产生的拉剪应力为主,钻孔孔间围岩状态随之由孔间围岩弱化阶段过渡到孔壁裂纹成形阶段,再转变为孔间围岩破断阶段。密集钻孔孔间围岩所受拉剪应力大小主要取决于关键岩层厚度及钻孔孔径与孔间距之比,与钻孔高度及间距成负相关,与角度及直径正相关。据此提出了密集钻孔关键参数确定方法,并根据龙滩矿3124 N工作面坚硬顶板条件设计了密集钻孔切顶留巷方案,确定钻孔长度为8.3 m,角度为15°,钻孔直径为48 mm,间距为500 mm。留巷后巷道顶帮变形可控且整体稳定性较好,由此可证明密集钻孔布置参数较为合理,密集钻孔关键参数确定方法有效可行。

短期淹水胁迫和解除胁迫对诺丽生理及产量的影响

海南是我国诺丽主产区,夏季台风导致的短期淹水胁迫频发,但目前鲜有诺丽应对短期淹水胁迫和胁迫解除后生理响应研究,且胁迫对产量的影响尚不明晰。本研究以生长6个月的诺丽幼苗为试验材料,采用盆栽连续浸没15 d的方法模拟短期淹水胁迫,在淹水后第1、3、7、10、15天时测定植株地上部和地下部干重、叶片净光合速率(P_(n))、脯氨酸(Pro)含量、根系活力(TTC)、根系丙二醛(MDA)、过氧化物酶(POD)、超氧化物歧化酶(SOD)等指标,并于解除胁迫后第1、7、15天测定相关指标,在主产区选取淹水和不淹水地块连续3 a测定产量。结果表明:诺丽受淹水胁迫后生理响应迅速,较不淹水对照处理,淹水第1天时叶片P_(n)下降,Pro含量增加,根系中MDA含量上升,根系活性下降,POD和SOD等抗氧化酶活性增加,这些指标在前7 d内均变化显著。而7 d后,除TTC和SOD活性仍显著变化外,其他指标的变化程度趋缓,表明叶片和根系逐步适应淹水胁迫;诺丽生物量根冠比(RSR)在淹水初期保持不变,但在3 d后显著下降,也在一定程度反映了诺丽植株短期内即已响应淹水胁迫;胁迫解除后各生理过程逐步恢复,在15 d时,诺丽光合作用、TTC基本恢复,但MDA等过氧化物含量仍然显著高于对照,表明前期胁迫形成的过氧化物其毒害作用短期难以消除。主产区多年多点的产量也表明,短期但频繁的淹水胁迫会导致产量大幅下降,降幅在21.64%~35.21%,这可能与胁迫造成的过氧化物毒害有关。因此,短期淹水胁迫不仅在胁迫期间对诺丽生理过程有较大影响,而且在胁迫解除后其不利影响仍长期存在,从而影响植株生长与产量。因此,在种植诺丽时应考虑地势较高且排水较好的地块,并做好排水系统;在易积水种植区,应在72 h内排走积水,可将影响降至最低。

短期驯化对水芹耐低盐胁迫的影响

为探究低盐胁迫对水芹(Oenanthe javanica)生长的影响和短期驯化在提升其耐盐度方面的效果,本研究评估并对比了54 d内,盐度为2 PSU(practical salinity units,实用盐度)、4 PSU、6 PSU和8 PSU的低盐胁迫对驯化与未驯化水芹生长状态和生理生化的影响。在水培条件下,采用每3 d提升2 PSU的方法对水芹进行驯化。结果显示,经过54 d的胁迫,短期驯化与未驯化的水芹最高均可在6 PSU盐度条件下存活,而盐度差异和短期驯化显著影响了水芹的生长和生化过程。相比对照组,胁迫盐浓度超过2 PSU时,盐胁迫导致水芹的鲜重、株高、根长、叶片数和叶绿素等增长率分别显著下降126.0%~199.4%、67.5%~124.0%、63.4%~83.2%、154.1%~325.0%和21.0%~52.6%,而驯化后仅分别下降40.7%~185.7%、25.0%~83.5%、37.8%~57.2%、62.7%~294.7%和7.5%~37.8%;盐胁迫导致水芹叶片的相对含水率降低率显著升高4.8%~6.4%,而驯化后仅升高2.9%~3.4%;盐胁迫导致水芹叶片的丙二醛和脯氨酸含量分别显著上升39.6%~52.9%和25.1%~30.9%,而驯化后分别上升25.4%~46.8%和36.1%~43.3%;盐胁迫导致水芹叶片的活性氧含量显著上升23.4%~29.5%,而驯化后仅上升7.4%~22.1%;盐胁迫导致水芹叶片的超氧化物歧化酶、过氧化物酶、抗坏血酸过氧化物酶、谷胱甘肽过氧化物酶和过氧化氢酶活性分别上升20.1%~27.2%、19.2%~25.0%、7.3%~17.0%、15.6%~27.7%和10.3%~18.1%,而驯化后分别上升29.8%~37.8%、33.9%~39.1%、27.9%~32.3%、28.5%~37.4%和28.0%~33.7%;盐胁迫导致叶片和根系K^(+)/Na^(+)比值分别显著下降67.5%~97.5%和76.8%~93.8%,而驯化后仅分别下降39.4%~89.7%和40.9%~82.7%。综上,低盐胁迫对水芹的生长及其生理生化反应产生不同程度的负面影响,而短期驯化可减弱这种负面影响。

低温胁迫后紫花苜蓿叶片光合作用的恢复特性研究

为探究低温解除后苜蓿光合作用恢复过程中的限制位点,以‘新牧4号’和‘甘农5号’2个品种紫花苜蓿为材料,测定其低温胁迫及恢复过程中苜蓿叶片光合活性的变化。结果表明,低温胁迫下2个苜蓿品种叶片叶绿素含量、净光合速率以及光系统Ⅱ(photosystemⅡ,PSⅡ)活性显著下降,非光化学淬灭系数(nonphotochemical quenching factor,NPQ)显著上升,但对光系统Ⅰ(photosystemⅠ,PSⅠ)的活性无显著影响;其中,‘甘农5号’叶绿素对低温更敏感,含量下降较多。室温恢复72 h后,2个品种苜蓿叶片PSⅡ的活性及净光合速率都有上升但均未恢复至处理前水平;NPQ缓慢下降至处理前水平,‘甘农5号’NPQ较‘新牧4号’更高,表明在恢复过程中仍有过剩光能需通过NPQ消耗。苜蓿叶片的电子传递链在低温下受抑制显著,恢复72 h后PSⅡ受体侧活性基本恢复至处理前,而PSⅡ供体侧活性显著下降。2个品种苜蓿单位反应中心捕获的用于电子传递的能量(energy captured by unit reaction center for electron transfer,ETO/RC)和单位反应中心捕获的用于还原QA的能量(energy captured by the unit reaction center for reducing QA,TRO/RC)在低温处理72 h后显著下降,解除低温后恢复至处理前水平,且2个品种无显著差异;2个苜蓿品种单位反应中心耗散掉的能量(energy dissipated by the unit reaction center,DIO/RC)未恢复至处理前水平,且‘甘农5号’在恢复72 h后DIO/RC显著升高。综上,低温胁迫显著伤害紫花苜蓿叶片光合机构,降低了光合速率,光合速率未恢复到处理前与PSⅡ的活性显著相关,限制光合作用恢复的位点在其供体侧,非光化学淬灭是恢复24 h过剩光能的主要分配途径。

深井直覆硬厚顶板侧向破断模式及采动应力响应特征研究

针对深井“三巷布置”工作面临空巷强烈矿压显现现象,以煤层直覆硬厚顶板为工程背景,运用理论分析、相似模拟、现场实测等研究手段,分析直覆硬厚顶板侧向破断模式,揭示临空巷强矿压显现机制,明晰工作面采动应力响应特征。研究结果表明:直覆硬厚顶板破断后,在工作面侧向形成长悬臂-铰接结构,破断线位于采空区内。直覆硬厚顶板岩性特征和几何特征决定着临空巷矿压显现程度,顶板越硬或者越厚,采空区煤体周围越容易产生较高的应力集中。直覆硬厚顶板下巷道围岩应力集中程度高,且临空侧超前支承压力影响范围更广,应力集中程度更高,巷道矿压显现更为剧烈;煤柱上侧向支承压力呈“同步受力、同步增长”变化特征,进入采空区稳定阶段后支承压力表现L+W型应力特征,相邻待采工作面煤柱侧出现非对称的应力峰值,煤柱中部出现应力双峰。受侧向高应力影响,下一区段巷道围岩主要表现为两帮中下部剧烈变形。基于工作面直覆硬厚顶板侧向破断特征和强动载矿压显现机制,提出了顶板灾害超前治理、“浅部强力支护+深部多层次卸压”的防控技术体系,为采场岩层控制提供有益指导。

基于压力拱发展规律的隧道初次支护时机研究

本文依托济莱高铁宅科隧道工程,利用现场监测和FLAC 3D数值模拟的方法,基于隧道应力传递路径的改变探究压力拱形成机制和分布范围,得出隧道纵截面压力拱形态特征图,引入位移完成率衡量围岩的开挖扰动程度,建立位移完成率和应力释放率的对应关系,得到最优初次支护时机。研究结果表明:在隧道开挖过程中,上部围岩中应力逐渐偏转,围岩荷载逐渐向四周传递,最终达到新的应力平衡状态,即在隧道四周产生形成封闭环状应力现象的压力拱;隧道仰拱靠近拱脚部位围岩产生应力集中,在1.8 D(D为隧道截面宽度)范围内的围岩均参与成拱效应,承担隧道拱部上方的围岩荷载;对塑性区体积率进行计算与分析,认定70%~80%应力释放率较为缓慢,应作为最佳初期支护时间点;在开挖时隧道初期支护滞后于掌子面的距离宜控制在4.3~7.6 m。