四钼酸铵生产中的晶界开裂理论

通过对四钼酸铵(ATM)晶体的显微观察和组成的化学分析提出了晶界开裂理论(Crystalline interface cracking theory),其中包括硬开裂和软开裂。结果表明:在ATM的晶界和表面分别存在着晶界结晶水和表面水的内应力和外应力。必然导致ATM晶体的开裂,其中包括有序的软开裂和无序的硬开裂。软开裂与硬开裂比例的控制取决于干燥温度与结晶温度之间的差值及升温速率。差值越小,升温速率越低,软开裂ATM所占比例越大,干燥ATM及钼粉粒度分布越均匀,平均粒度越可控。因此,控制温度差值及升温速率对于ATM质量控制有着非常重要的作用。

黏性土渠道边坡的形成方式对滑坡的影响

黏性土渠道的运行期,挖方边坡比填方边坡更容易发生滑坡。土的密度愈大,开挖愈深,则挖方渠道边坡在运用过程中膨胀和强度降低愈多,其失稳的可能性就愈大。膨胀土加剧了强度降低的幅度。开裂硬黏土既加快强度降低的速度又加大软化区域。在边坡表面设置护坡不但能有效地防止即使是分散性黏土的淘刷,还在不同程度上抑制或推迟表层滑坡和粉土的冻胀。文中建议的确定挖方渠坡抗剪强度的方法与国内流行方法略有差别。

Numerical simulation of optimum mining design for high stress hard-rock deposit based on inducing fracturing mechanism

The 3D numerical simulation model of deep hard-rock deposit in Kaiyang Phosphate Mine of Guiyang was established based on the practical engineering using 3DEC numerical simulation software. The distribution characteristics of displacement fields and plastic zones of the orebody were simulated in three different excavation cases, including the case of excavation artificial inducted roadway in the orebody, the case of horizontal or vertical excavation direction and the case of the upward or downward excavation order. The simulation results indicate that the plastic zone and displacement field of surrounding rock around the inducted roadway are continuously increasing with the increase of the exposure time after digging an artificial inducted roadway in the orebody. Thus the raw rock ore becomes easier to be fragmented, which provides advantageous conditions for roadheader to cut high stress hard-rock. It is worthy noting that there is a large difference in effective utilization of deep ground pressure between horizontal and vertical excavation directions. The later can produce larger deformation and fracture zone than the former on the rock mass around the deduced roadway, which means that the later may utilize the high ground pressure more effectively to break hard-rock. And the obtained results also show that upward excavation order is more helpful for ground pressure to break rock than downward excavation order.

Role of matrix structure and flaw size distribution modification on deflection hardening behavior of polyvinyl alcohol fiber reinforced engineered cementitious composites(PVA-ECC)

The multiple cracking and deflection hardening performance of polyvinyl alcohol fiber reinforced engineered cementitious composites(PVA-ECC)under four-point flexural loading have been investigated.Matrices with different binder combinations and W/B ratios(from 0.44 to 0.78)providing satisfactory PVA fiber dispersion were specially designed.Effect of pre-existing flaw size distribution modification on deflection hardening behavior was comparatively studied by adding 3 mm diameter polyethylene beads into the mixtures(6%by total volume).Natural flaw size distributions of composites without beads were determined by cross sectional analysis.The crack number and crack width distributions of specimens after flexural loading were characterized and the possible causes of changes in multiple cracking and deflection hardening behavior by flaw size distribution modification were discussed.Promising results from the view point of deflection hardening behavior were obtained from metakaolin incorporated and flaw size distribution modified PVA-ECCs prepared with W/B=0.53.The dual roles of W/B ratio and superplasticizer content on flaw size distribution,cracking potential and fiber-matrix bond behavior were evaluated.Flaw size distribution modification is found beneficial in terms of ductility improvement at an optimized W/B ratio.

Tunnel failure in hard rock with multiple weak planes due to excavation unloading of in-situ stress

Natural geological structures in rock(e.g.,joints,weakness planes,defects)play a vital role in the stability of tunnels and underground operations during construction.We investigated the failure characteristics of a deep circular tunnel in a rock mass with multiple weakness planes using a 2D combined finite element method/discrete element method(FEM/DEM).Conventional triaxial compression tests were performed on typical hard rock(marble)specimens under a range of confinement stress conditions to validate the rationale and accuracy of the proposed numerical approach.Parametric analysis was subsequently conducted to investigate the influence of inclination angle,and length on the crack propagation behavior,failure mode,energy evolution,and displacement distribution of the surrounding rock.The results show that the inclination angle strongly affects tunnel stability,and the failure intensity and damage range increase with increasing inclination angle and then decrease.The dynamic disasters are more likely with increasing weak plane length.Shearing and sliding along multiple weak planes are also consistently accompanied by kinetic energy fluctuations and surges after unloading,which implies a potentially violent dynamic response around a deeply-buried tunnel.Interactions between slabbing and shearing near the excavation boundaries are also discussed.The results presented here provide important insight into deep tunnel failure in hard rock influenced by both unloading disturbance and tectonic activation.

Control effect of fracture on hard coal cracking in a fully mechanized longwall top coal caving face

Through theoretical analysis, simulation test and practice, the law of a fracture'sinfluence on hard top coal press cracking was studied. The study focused on the relationbetween fracture and coal strength, top coal caving ability and work face layout. Based onthe investigation of the fracture system, the control of press cracking was achieved bymatching working face to fracture orientation to improve top-coal caving ability and recovery. The matching principle was pointed out: The top-coal caving working face should beperpendicular to or obliquely cross the primary fracture at a large angle, and cross thesecondary fracture at a small angle. The rational match can increase the recovery ratio oftop-coal and avoid rib spalling. The application of control technology on hard top coalpress cracking was introduced at the Iongwall top-coal caving face.

PU诊所

如何增加流动性；

Preparation and properties of a new cutting pick of coal shearers

Reliability and wear resistance of cutting picks play a significant role in coal mine exploitation with coal shearers.Tool bit separation,blade breaking,severe erosion of the cutting body and fatigue fractures are the main reasons for failure of cutting picks.We carried out carburization on a 30CrMnMo alloy to synthesize a new cutting pick material with improved mechanical properties and high wear resistance.The results indicated that carburization can effectively strengthen the surface of the 30CrMnMo alloy by forming a thick carburized layer and thus significantly improve the surface hardness and wear resistance.In addition,the excellent toughness of 30CrMnMo alloy as a substrate of cutting picks can prevent brittle ruptures and fatigue fractures under high impact stress conditions.The significant decrease in both frictional coefficient and rate of erosion of this carburized 30CrMnMo alloy suggests that this alloy is a potential material for cutting picks of coal shearers after rational carburization.