Advanced Materials Research Vols. 455-456

Abstract: The main lithology of the formation under Permian in Malang sag is basalt, with the characteristic of strong abrasive and low drillability the ROP (rate of penetration) is low. This paper based on drillability experiment of the core from oilfield, established rock drillability model, computed the drillability grade of cone bit and PDC bits, optimized the bit combined with the bit structural features, the result indicates that in the basalt formation under Permian with low ROP the ROP enhanced more than 50% using the recommended bit, the research improved ROP drastically, shorten the drilling cycle, which attained the aim of excellent and fast drilling, and has an important instruction meaning for bit optimization of basalt formation.

Abstract: Based on a practical engineering, considering the characteristics such as shallow,weaking surrounding rock, large span, double-arch of the tunnel, the stress and strain of surrounding rocks, support structure and mid-wall were analyzed by FEM for different excavating procedure. The simulation results were compared with in-situ monitoring results. The crown settlement and convergence displacement are divided two obvious increasing stages. Surrounding rock upper and under the mid-wall generate bigger plastic strain and should be strengthened. Temporary support of the pilot bears bigger load and should be reinforced. Bearing bigger horizontal direction tensile stress and uneven load, the bottom of mid-wall must have enough reinforcing steel bar or employ augment foundation. The analysis results provide a scientific basis and technical guidance for the construction optimization of the tunnel constructed by three-pilot excavation method.

Abstract: The modeling method for freezing tunnel with fractured surrounding rock is discussed. Frost weathering of rock in cold regions poses serious threat to the stability of geotechnical engineering. Fracture in the freezing rock plays an important role in the mechanical features of the rock mass. However, most of the previous study on freezing rock considered the rock as continuous media, in which the effects of fracture are not reflected sufficiently. This paper overcomes the above-mentioned insufficient and considers the fracture as an important factor while modeling. The model of frost fracture is built by AutoCAD and then transferred into ANSYS for meshing, and finally imported into FLAC3D for calculating by converting procedure. The method of equivalent coefficient of thermal expansion is used to simulate the expansion of water while freezing. The stress and thermal fields after some steps of calculation are ultimately simulated and the influence of fractures is reflected in the results.

Abstract: Based on rock Mechanical theory under unloading, according to the analysis of rock mechanics state of pre and post excavation of the layered dip rocky slope, it was found that excavation unloading cause deterioration of rock constitutive relation and structure plane’s mechanical parameters, deformation mechanism of high layered dip rocky slope was analyses when rock is at unloading condition in this study. Its deformation consists of the two parts which are rock mass unloading rock mass springback displacement and bedding-slip displacement along the rock mass discontinuity, and deduced the calculating formula of slope displacement. Research results with great guide significance and practical engineering value to similar engineering construction afterward.

Abstract: Well KL11-2-1 is a wildcat well that located in KL11-2 structure, where sticking happened in position Ⅳ of Shahejie group, the accident happened again in the same position while drilling the sidetracked well KL11-2-1S on the base of Well KL11-2-1, Analysis reveals that the lithology in the place of the two sticking accidents is rufous mudstone. This kind of mudstone has the character of strong plasticity, swelling with water and very soft, the main reason of sticking is that the mud column pressure can not balance the soft mudstone creep pressure and the creep lead to borehole shrinkage. For solve the problem during drilling in this structure, this paper according to the characteristics of mudstone in this structure builted proper creep equation and creep mechanical computation module of soft mudstone, applied FLAC3D software to compute and analyze the creep characteristics, obtain borehole shrinkage rate plate with different depth and mud density, and the safe mud density that can inhibit the creep which lead to borehole shrinkage is given, the results show that for prevent the sticking accident occurred the safe mud density of the two sticking points of the well KL11-2-1/1S is 1.73 g/cm3 and 1.75 g/cm3.the results make significant sense in guiding the subsequent drill of the structure.

Abstract: Being the face slabs of high concrete faced rockfill dams (CFRD) are under complex stress state, the slabs are relative vulnerable. And crack is easy to form on slab, which can influence durability and integrity, then weaken impermeable ability and safety of dam. The factors that contribute to the structural cracks, non-structural cracks and extruding cracks of concrete face-slab are analyzed in detail. The result shows that the structural crack is mainly due to differential settlement, the extruding crack in riverbed position is mainly caused by rockfill body over-settlement of dam beyond 150m high and the non-structural crack is mainly caused by temperature shrinkage and air shrinkage. Therefore, crack control of CFRD face slab should be regulated by the three means coming from structural design, construction control and concrete material. It is proved by the practices in Shuibuya CFRD that face slab cracks on CFRD beyond 200m high can be reduced effectually by the present technique means.

Abstract: In this paper, fluoroalkylsilane (F₃C-(CF₂)₅-(CH₂)₂-Si (OC₂H₅)_3, F-8261) was successfully used as surface modifier to prepare oleophobic hollow microspheres. Three-phase foam was directly fabricated by oleophobic hollow microspheres. The result shows that outstanding improvement in the stability and anti-burning properties of three-phase foam on oil were achieved through the oleophobic modification. The optimum reaction conditions were 12% of fire fighting protein，the addition of 50% of hollow microsphere and0.5% F-8261.

Abstract: In this paper, pumpkin juice concentrations were carried out using a three-phase circulating fluidized bed evaporator. The flow and heat transfer characteristics of this evaporation process were investigated and parametric studies were conducted to identify the governing parameters in the process. It was found that compared with two-phase evaporation process, addition of inert particles improved the heat transfer efficiency by 35% and also inhibit forming and clean fouls during the pumpkin juice concentration. A correlation equation of boiling heat transfer coefficient was established for the three-phase circulating fluidized bed evaporator. This research work improves the understanding of the three-phase circulating fluidized bed evaporator and benefit to its wider application in foodstuff field.

Abstract: This paper presents the disturbance compensation scheme based on liquid crystal steering system according to the problem that satellite platform vibration affects the tracking and pointing accuracy in space optical communication. The mathematical model of liquid crystal steering system is built. For improving convergence speed, the adaptive controller based on posteriori estimation errors RLS lattice filter is designed, which not only achieves fast adaptation, but also reaches optimal steady-state disturbance compensation. Finally, the simulation results show that this control scheme is valid and feasible.