新型抗压式压力平衡风门的研制与应用

针对漳村煤矿井下现用风门存在的问题及矿压显现强烈的特点,研制了新型抗压式压力平衡风门,其技术关键在于采用双层门框墙结构形式代替原有单层门框墙结构形式,外层辅框直接与巷道断面墙接触,使得内层主框有效避开与巷道断面墙的接触。通过漳村煤矿的现场应用,展示了其技术优势及推广应用前景。

囊压式扩体抗浮锚杆承载特性和工程应用建议

针对兰州第三系风化红砂岩遇水软化崩解、扰动后强度急剧降低、抗浮锚杆质量难以保证等问题,在现场拉拔试验基础上,分析了囊压式扩体抗浮锚杆的荷载-位移曲线、弹性和塑性变形规律、承载特性和破坏特征,从锚杆成孔方式、布置形式、锚杆长度、防排水措施和侧摩阻力的提高方法等方面给出囊压式扩体锚杆在丰水砂岩中的工程应用建议。

压差式自动安全抗浮系统在污水处理厂构筑物抗浮设计中的应用

针对目前污水处理厂构筑物常用抗浮方法存在投资成本高、施工难度大、管理复杂等问题,提出一种新型的压差式自动安全抗浮系统,介绍了该抗浮系统的抗浮原理、设计思路、技术特点和注意事项。以云南曲靖市污水处理厂改建工程中的A/O池抗浮设计为例,详细介绍了压差式自动安全抗浮系统在污水处理厂设计中的应用。实践表明,该系统具有自动、安全、定压、可靠的抗浮功能,同时节省地基处理费,减小施工周期等特点。

前撑式注浆管在深基坑工程中的应用

依托上海浦东新区康桥工业区租赁住房项目的深基坑施工案例,论证了前撑式注浆钢管围护体系的可行性。从基坑开挖到地库底板完成,监测发现基坑最大位移与周边土体沉降均在可控范围,说明前撑式注浆钢管支撑技术具有施工简单、造价低、工期短等特点,为该技术在其他类似工程中的推广起到了借鉴作用。

Static and dynamic tensile failure characteristics of rock based on splitting test of circular ring

Static and dynamic splitting tests were conducted on ring marble specimens with different internal diameters to study the tensile strength and failure modes with the change of the ratio of internal radius to external radius （ρ） under different loading rates. The results show that the dynamic tensile strength of disc rock specimen is approximately five times its static tensile strength. The failure modes of ring specimens are related to the dimension of the internal hole and loading rate. Under static loading tests, when the ratio of internal radius to external radius of the rock ring is small enough （ρ〈0.3）, specimens mostly split along the diametral loading line. With the increase of the ratio, the secondary cracks are formed in the direction perpendicular to the loading line. Under dynamic loading tests, specimens usually break up into four pieces. When the ratio ρreaches 0.5, the secondary cracks are formed near the input bar. The tensile strength calculated by Hobbs’ formula is greater than the Brazilian splitting strength. The peak load and the radius ratio show a negative exponential relationship under static test. Using ring specimen to determine tensile strength of rock material is more like a test indicator rather than the material properties.

Dynamic compressive strength and failure mechanisms of microwave damaged sandstone subjected to intermediate loading rate

To investigate the influence of microwave heating on the dynamic behavior and failure mechanisms of rock,dynamic compression tests were conducted on microwave-irradiated sandstone specimens using a modified split Hopkinson pressure bar(SHPB)system.Experimental results show that microwave radiation can effectively weaken the compressive strength of sandstone.Rock specimens show three different failure modes under impact load:tensile failure,tensile−shear composite failure and compressive−shear failure.The dynamic Poisson’s ratio,calculated using the measured P-and S-wave velocities,is introduced to describe the deformation characteristics of sandstone.With the increase in microwave power and heating time,the Poisson’s ratio declines first and then increases slightly,and the turning point occurs at 244.6℃.Moreover,the microstructural characteristics reveal that microwave radiation produces dehydration,pore expansion,and cracking of the rock.The damage mechanisms caused by microwave radiation are discussed based on thermal stress and steam pressure inside the rock,which provides a reasonable explanation for the experimental results.

Mathematical model analysis of new-type magnetic integrated CRT considering magnetic leakage

A novel magnetic integrated controllable reactor of transformer type(CRT)has the advantages of simple structure,flexible assembly,convenient maintenance and practicability.To analyze its operation characteristics accurately,we establish corresponding equivalent mathematical model considering magnetic leakage based on magnetic circuit and circuit dualistic transformation method.The distribution of magnetic leakage field of each winding is analyzed qualitatively,and the analytical calculation formulas of magnetizing inductance and leakage inductance of each winding are derived.Based on this,the analytical calculation formulas of short-circuit impedance and winding current of CRT under different working conditions are derived.The field-circuit coupling finite element model of the magnetic integrated CRT is established to simulate the current of each winding under different working conditions.The results show that the analytical calculation results of each winding current have good consistency with the finite element calculation results,indicating the validity of CRT equivalent mathematical model and correctness of the analytical formulas of leakage inductance,short-circuit impedance and winding current of CRT.The working winding current of CRT is increasing gradually with the operation of control winding in turn to realise the transition of CRT compensation capacity from zero to a rated value.

Analytical analysis of pullout resistance of the hydraulic expansion rockbolts on a frictionally coupled model

This paper proposes an empirical formula to estimate the shear strength of hydraulic expansion rockbolts.The field experimental results were obtained from eleven pullout tests to evaluate the results computed by the proposed formula.It was found that shear resistance of hydraulic expansion rockbolts significantly depends on the uniaxial compressive strength and elastic modulus of rock,with high correlation coefficients of 0.7651 and0.8587,respectively.The developed formula enables estimation of the maximum pullout load in an analytical process without pullout tests in the field.Conversely,due to the poor interlocking at the initial pullout load,the measured displacements were higher than the estimated ones.To reduce the interlocking effects between bolt and rock,we recommend preloading of 29.4 kN.Preload allows reducing the distance between the measured and estimated displacement and making two load-displacement curves practically identical with marginal differences of 1.1 to 1.5 mm at the maximum pullout load.