Dynamic response and failure process of horizontal-layered fractured structure rock slope under strong earthquake

Rock slope with horizontal-layered fractured structure(HLFS)has high stability in its natural state.However,a strong earthquake can induce rock fissure expansion,ultimately leading to slope failure.In this study,the dynamic response,failure mode,and spectral characteristics of rock slope with HLFS under strong earthquake conditions were investigated based on the large-scale shaking table model test.On this basis,multiple sets of numerical calculation models were further established by UDEC discrete element program.Five influencing factors were considered in the parametric study of numerical simulations,including slope height,slope angle,bedding-plane spacing and secondary joint spacing as well as bedrock dip angle.The results showed that the failure process of rock slope with HLFS under earthquake action is mainly divided into four phases,i.e.,the tensile crack of the slope shoulder joints and shear dislocation at the top bedding plane,the extension of vertical joint cracks and increase of shear displacement,the formation of step-through sliding surfaces and the instability,and finally collapse of fractured rock mass.The acceleration response of slopes exhibits elevation amplification effect and surface effect.Numerical simulations indicate that the seismic stability of slopes with HLFS exhibits a negative correlation with slope height and angle,but a positive correlation with bedding-plane spacing,joint spacing,and bedrock dip angle.The results of this study can provide a reference for seismic stability evaluation of weathered rock slopes.

Horizontal aquifer movement induced by groundwater pumping and its applications to the analysis of some geological disasters

Based on Darcy Gersevanov law concerning a flow relation between water and solids, we derive the horizontal movement of solid frame resulted from a discharging well in a Theis Thiem confined system, and further analyze the relations among the horizontal movements and pumped time t as well as radius r from the discharging well. As applications of the theory, we propose some new interperations for ground fissure activity and casing failures induced by groundwater withdrawal or injection.

Mechanical property design method of cement sheath in a horizontal shale oil well under fracturing conditions

Based on the elastoplastic model of cement sheath considering the influence of three-dimensional principal stress and the stress field model of interface crack,a mechanical performance design method of cement sheath is established to meet the wellbore sealing requirements during fracturing.This method takes the failure types of the cement sheath,such as tensile failure,plastic yield,interface crack propagation along interface and zigzag propagation into account.Meanwhile,the elasticity modulus and Poisson's ratio quantitative design charts of cement sheath are constructed based on this method,and the safety and risk areas of wellbores are defined,which quantify the yield strength and tensile strength indexes of cement sheath.The results show that decreasing elasticity modulus,increasing yield strength and Poisson's ratio of cement sheath can avoid plastic deformation of cement sheath;increasing the tensile strength of cement sheath can prevent its tensile failure;increasing elasticity modulus and Poisson's ratio of cement sheath is good for shortening the length of the interface crack,but will increase the risk of interface cracks zigzagging into cement sheath.The model calculation and case verification has proved that the method in this paper can give accurate calculation results and is convenient for field application.

Stability analysis of seabed strata and casing structure during the natural gas hydrates exploitation by depressurization in horizontal wells in South China Sea

Natural gas hydrates(NGHs)are a new type of clean energy with great development potential.However,it is urgent to achieve safe and economical NGHs development and utilization.This study established a physical model of the study area using the FLAC^(3D) software based on the key parameters of the NGHs production test area in the South China Sea,including the depressurization method,and mechanical parameters of strata,NGHs occurrence characteristics,and the technological characteristics of horizontal wells.Moreover,this study explored the law of influences of the NGHs dissociation range on the stability of the overburden strata and the casing structure of a horizontal well.The results are as follows.With the dissociation of NGHs,the overburden strata of the NGHs dissociation zone subsided and formed funnelshaped zones and then gradually stabilized.However,the upper interface of the NGHs dissociation zone showed significant redistribution and discontinuity of stress.Specifically,distinct stress concentration and corresponding large deformation occurred in the build-up section of the horizontal well,which was thus prone to suffering shear failure.Moreover,apparent end effects occurred at the end of the horizontal well section and might cause the deformation and failure of the casing structure.Therefore,it is necessary to take measures in the build-up section and at the end of the horizontal section of the horizontal well to prevent damage and ensure the wellbore safety in the long-term NGHs exploitation.

Upper-Bound Limit Analysis of the Multi-Layer Slope Stability and Failure Mode Based on Generalized Horizontal Slice Method

Multi-layer slopes are widely found in clay residue receiving fields.A generalized horizontal slice method(GHSM)for assessing the stability of multi-layer slopes that considers the energy dissipation between adjacent horizontal slices is presented.In view of the upper-bound limit analysis theory,the energy equation is derived and the ultimate failure mode is generated by comparing the sliding surface passing through the slope toe(mode A)with that below(mode B).In addition,the influence of the number of slices on the stability coefficients in the GHSM is studied and the stable value is obtained.Compared to the original method(Chen’s method),the GHSM can acquire more precise results,which takes into account the energy dissipation in the inner sliding soil mass.Moreover,the GHSM,limit equilibrium method(LEM)and numerical simulation method(NSM)are applied to analyze the stability of a multi-layer slope with different slope angles and the results of the safety factor and failure mode are very close in each case.The ultimate failure modes are shown to be mode B when the slope angle is not more than 28°.It illustrates that the determination of the ultimate sliding surface requires comparison of multiple failure modes,not only mode A.

Fault Tree Analysis of Feeding Control System for Computer Numerical Control Heavy-Duty Horizontal Lathes with Multiple Common Cause Failure Groups

The lathes are basic machine tools for manufacturing cylindrical parts. In recent years, the DLseries computer numerical control(CNC) heavy-duty horizontal lathes(HDHLs) have been widely used in the transportation, energy and aviation industries. High availability of the CNC heavy-duty lathes is demanded to guarantee the efficiency and benefit of these manufacturing industries. As one of the key subsystems of the HDHLs, the feeding control system is studied in this paper on reliability modeling and reliability analysis. The fault tree analysis(FTA) method is used for reliability modelling of the feeding control system. Considering the multiple common cause failure groups(CCFGs) existing in the system, a modified beta factor parametric model is introduced to model the common cause failure(CCF) in system. The reliability of feeding control system is then obtained and the effect of CCF on the reliability of the whole system is studied as well.

圆钢管型钢再生混凝土组合柱水平承载力计算方法研究

通过对11个圆钢管型钢再生混凝土组合柱进行低周反复荷载试验,分析再生粗骨料取代率、型钢截面形式、轴压比、型钢配钢率及圆钢管壁厚参数对组合柱水平承载力的影响规律;观察了组合柱的破坏形态及特征,研究了圆钢管、型钢翼缘及腹板应变的发展规律,分析了组合柱的地震破坏特征。研究表明,在水平地震作用下组合柱发生典型的压弯塑性铰破坏。在此基础上,结合现有规范提出了基于叠加原理的圆钢管型钢再生混凝土组合柱水平承载力计算方法。计算结果表明,其水平承载力计算值与试验值吻合度较好,能较为准确地预测组合柱的水平承载力。

Restraint effect of partition wall on the tunnel floor heave in layered rock mass

The presence of horizontal layered rocks in tunnel engineering significantly impacts the stability and strength of the surrounding rock mass,leading to floor heave in the tunnel.This study focused on preparing layered specimens of rock-like material with varying thickness to investigate the failure behaviors of tunnel floors.The results indicate that thin-layered rock mass exhibits weak interlayer bonding,causing rock layers near the surface to buckle and break upwards when subjected to horizontal squeezing.With an increase in the layer thickness,a transition in failure mode occurs from upward buckling to shear failure along the plane,leading to a noticeable reduction in floor heave deformation.The primary cause of significant deformation in floor heave is upward buckling failure.To address this issue,the study proposes the installation of a partition wall in the middle of the floor to mitigate heave deformation of the rock layers.The results demonstrate that the partition wall has a considerable stabilizing effect on the floor,reducing the zone of buckling failure and minimizing floor heave deformation.It is crucial for the partition wall to be sufficiently high to prevent buckling failure and ensure stability.Through simulation calculations on an engineering example,it is confirmed that implementing a partition wall can effectively reduce floor heave and enhance the stability of tunnel floor.

星罩组合体水平运输辅助支撑机构设计方案

针对星罩组合体水平运输条件下星箭分离装置的疲劳破坏问题,提出增加卫星辅助支撑机构的设计方案。建立辅助支撑机构力学模型,利用解析法计算得到辅助支撑机构设计的重要输入指标;并通过有限元仿真验证辅助支撑机构的性能是否满足使用要求。该辅助支撑机构的设计贯彻了从设计输入、建模、计算到验证的全流程研究方法,可为后续星罩组合体水平运输提供参考。

Deterministic and probabilistic analysis of great-depth braced excavations:A 32 m excavation case study in Paris

The Fort d’Issy-Vanves-Clamart(FIVC)braced excavation in France is analyzed to provide insights into the geotechnical serviceability assessment of excavations at great depth within deterministic and probabilistic frameworks.The FIVC excavation is excavated at 32 m below the ground surface in Parisian sedimentary basin and a plane-strain finite element analysis is implemented to examine the wall deflections and ground surface settlements.A stochastic finite element method based on the polynomial chaos Kriging metamodel(MSFEM)is then proposed for the probabilistic analyses.Comparisons with field measurements and former studies are carried out.Several academic cases are then conducted to investigate the great-depth excavation stability regarding the maximum horizontal wall deflection and maximum ground surface settlement.The results indicate that the proposed MSFEM is effective for probabilistic analyses and can provide useful insights for the excavation design and construction.A sensitivity analysis for seven considered random parameters is then implemented.The soil friction angle at the excavation bottom layer is the most significant one for design.The soil-wall interaction effects on the excavation stability are also given.

Analytical investigations of in situ stress inversion from borehole breakout geometries

This study aims to investigate the feasibility of deriving in situ horizontal stresses from the breakout width and depth using the analytical method.Twenty-three breakout data with different borehole sizes were collected and three failure criteria were studied.Based on the Kirsch equations,relatively accurate major horizontal stress(sH)estimations from known minor horizontal stress(sh)were achieved with percentage errors ranging from 0.33%to 44.08%using the breakout width.The Mogi-Coulomb failure criterion(average error:13.1%)outperformed modified Wiebols-Cook(average error:19.09%)and modified Lade(average error:18.09%)failure criteria.However,none of the tested constitutive models could yield reasonable sh predictions from known sH using the same approach due to the analytical expression of the redistributed stress and the nature of the constitutive models.In consideration of this issue,the horizontal stress ratio(sH/sh)is suggested as an alternative input,which could estimate both sH and sh with the same level of accuracy.Moreover,the estimation accuracies for both large-scale and laboratory-scale breakouts are comparable,suggesting the applicability of this approach across different breakout sizes.For breakout depth,conformal mapping and complex variable method were used to calculate the stress concentration around the breakout tip,allowing the expression of redistributed stresses using binomials composed of sH and sh.Nevertheless,analysis of the breakout depth stabilisation mechanism indicates that additional parameters are required to utilise normalised breakout depth for stress estimation compared to breakout width.These parameters are challenging to obtain,especially under field conditions,meaning utilising normalised breakout depth analytically in practical applications faces significant challenges and remains infeasible at this stage.Nonetheless,the normalised breakout depth should still be considered a critical input for any empirical and statistical stress estimation method given its significant correlation with horizontal stresses.The outcome of this paper is expected to contribute valuable insights into the breakout stabilisation mechanisms and estimation of in situ stress magnitudes based on borehole breakout geometries.

推扭(H-T)荷载作用下刚性矩形基础承载特性研究

现行杆件基础设计仅考虑水平力(H)而忽略扭矩(T)的作用,这很可能导致杆件基础发生推扭破坏。为分析推扭(H-T)荷载下刚性矩形基础的承载特性,首先根据杆件基础的受力特点,建立了相应的简化计算模型,推导了T、H-偏心弯矩(M)2种承载模式下基础受力与变形分析的理论解答;其次通过数值模拟分析,获得了H-T荷载下矩形刚性基础的破坏包络线;在此基础上,通过室内模型试验验证了理论计算方法的合理性,并探讨了扭推比、地基抗力比例系数m值对基础受力与变形的影响。研究发现:H-T荷载下刚性矩形基础的破坏包络线近似呈抛物线分布;随扭推比增大,矩形基础的地基承载力随之减小,其破坏模式也由水平变形破坏转为扭转变形破坏;增大m值,可有效减小基础地面处水平位移及旋转角度。为确保刚性矩形基础的安全稳定,其上覆回填土体性质和压实度均应满足设计要求。上述结论可为多杆合一杆件基础的设计提供参考。

推扭荷载作用下刚性扩大基础设计计算方法

多杆合一杆件基础在风荷载作用下受到水平力、弯矩及扭矩的作用,而现行杆件基础设计中并未考虑扭矩,这可能导致基础发生扭转破坏。根据杆件基础的受力形式,建立了对应的简化计算模型,对水平力⁃偏心弯矩、扭矩两种承载工况下基础受力与变形进行理论分析,进一步得到推扭荷载作用下扩大刚性基础的破坏包络线。分析不同高长比对其破坏包络线的影响,并对其进行拟合,得到其理论解答。采用室内模型试验对理论计算方法进行验证。

水平层状复合岩体变形破坏特征的围压效应研究

为研究不同围压下深部复合地层岩体变形和破坏特征,结合地质赋存条件制作了类层状复合岩石试样,通过开展不同围压下的三轴压缩试验,研究了围压对水平层状复合岩体变形破坏特征的影响。试验结果表明:随着围压的不断增加,峰后偏应力-应变曲线的降低速率逐渐变缓,应变软化程度逐渐减弱;随着围压的增大,水平层状复合岩石的破坏形态呈现出明显差异,整体上破坏形态逐渐由脆性破坏向延性破坏过渡;在一定围压状态下,围压对软岩膨胀变形的约束效果相对硬岩较弱,导致水平层状复合岩石试样的软、硬分层之间的膨胀变形不协调,在层间黏结力作用下,软、硬分层之间发生相对错动现象。该研究成果对于施工单位预防深部复合地层隧道掘进机(TBM)工程灾害具有一定的指导意义。

外包钢-混凝土组合简支梁试验研究

外包钢-混凝土组合梁是在由冷弯薄壁型钢与厚钢板焊接成的U型钢梁内浇注混凝土构件,并用必要的构造措施使型钢和混凝土共同工作。为研究这种新型组合梁的受力性能,完成了10根外包钢-混凝土组合简支梁受弯试验。试验结果证明这种组合梁具有较优越的力学性能,但在受力过程中存在两个受力薄弱面,薄弱面的破坏会导致新型组合梁发生纵向水平剪切破坏和纵向滑移破坏,需在设计中避免。

页岩气储层井壁坍塌压力研究

页岩气储层各向异性强,易发生井壁失稳。利用四川盆地所取页岩气储层岩芯测试钻井液对页岩基体及层理面强度的影响规律,结合单一弱面准则,建立页岩气井井壁稳定预测模型,分析层理面倾角、钻井方位、钻井时间及钻井液类型等因素对页岩储层水平井坍塌压力的影响规律。研究结果表明:层理面倾角小于45°时,井壁岩石发生层理面破坏,倾角大于45°时,在某些井眼方位井壁会发生本体破坏;沿最小水平地应力方位附近钻进水平井最容易发生井壁坍塌;随钻井时间的增加,坍塌压力逐渐升高,井壁破坏形式可能会由初始的页岩基体破坏变为层理面破坏;使用油基钻井液比使用水基钻井液更容易保持井壁的长期稳定。研究结果可以为页岩气井钻井设计提供参考依据。

高水平应力巷道连续“双壳”治理底臌实验研究

基于深井工程软岩巷道严重底臌这一状况,以河北陶二煤矿扩大区北大巷条件为工程背景,对连续"双壳"如何有效控制深井软岩巷道底臌进行了实验研究。通过现场地应力测量、解算,确定了巷道围岩应力状态,采用自行设计的双向加载试验台,进行深井软岩巷道不同侧压系数时底板围岩变形失稳特征的相似模拟实验,得到底板位移场变化规律及围岩应力分布状态。模拟实验结果表明:底板连续"双壳"加固巷道底臌量较原支护巷道平均减小53%;底板浅孔注浆(浅部壳体)提高岩体承载能力,深孔锚索束注浆(深部壳体)扩大岩体承载范围,浅深壳体共同承载、协同变形有效控制了底板围岩稳定。最后揭示了连续"双壳"治理底臌机理。

H油田超深水平井套损机理及防诊治技术研究

塔里木盆地H油田,整体采用超深水平井开发,近年套损现象呈增加趋势,给生产造成被动。针对该现状,实施多学科协作攻关,系统研究套损平面与纵向分布规律,重点开展物理与化学机理研究,明确提出油藏与钻井、测井、井下技术相结合的套损"防诊治"一体化研究思路。经实践证明,预测的套损隐患井与实际吻合程度及套损井恢复率均较高,成功探索了超深水平井套损对策技术,为其他类似油田提供了有益借鉴。

钙释放通道稳定蛋白过度表达对心力衰竭心室肌细胞肌浆网功能的影响

目的:探讨钙释放通道稳定蛋白FKBP12.6过度表达对心力衰竭心室肌细胞肌浆网(SR)功能的影响。方法:用携带FKBP12.6基因的重组腺病毒Ad.FKBP12.6-GFP感染分离的心力衰竭心室肌细胞,通过RT-PCR和Western blotting技术检测转基因的表达;通过局部场刺激诱发胞内钙瞬变,SR钙容量则由咖啡因诱发的钙释放估测;以X-rhod-1-AM作为Ca2+指示剂,采用激光共聚焦线扫描检测细胞内Ca2+浓度的变化。结果:Ad-FKBP12.6-GFP组的FKBP12.6mRNA和蛋白表达水平分别比对照组升高5倍和4倍;Ad-FKBP12.6-GFP感染细胞的钙瞬变幅度(F/F0峰值,3.16±0.42vs1.43±0.38,P<0.01)和SR钙容量(F/F0峰值,4.15±0.54vs2.23±0.44,P<0.01)均显著高于Ad-GFP感染细胞。结论:采用基因转移技术上调FKBP12.6的表达可能是心力衰竭治疗的一条新途径。

煤层分支水平井井眼稳定性模拟研究

应用分支水平井技术开发煤岩气藏,具有单井产量高、采出程度高、经济效益好的优势。如何保证分支连接处的力学完整性、水力完整性和再进入能力,是煤层分支水平井顺利实施的关键技术。根据煤岩力学性质特征,运用有限元力学理论建立了数值模拟模型,对煤层分支水平井的井眼稳定性进行了分析。结果表明,分支水平井在井眼连接段出现应力集中;分支井眼与主井眼夹角为15°时,随压差的增大该处应力集中更加严重,同时连接井段随着井筒压差的增大有发生失效破坏的可能性。通过对比夹角为60°和15°时的结果得出,夹角增大有利于井眼稳定。该认识对于煤层气井的保护储层钻井、完井和生产设计具有重要意义,可进一步推广应用。