Applied Mechanics and Materials Vols. 170-173

Abstract: CCSD-SK1 well was the first Cretaceous scientific drilling well in the world, locating in Songliao basin, Northeast China. It included main well (also called north well) and south well. This paper introduced the anti-collapse drilling fluid technology in main well where the desired continuous coring section was from 164.77 m to 1792.00 m. Continuous technical barriers challenged the intelligence of drilling engineers of this project. First, preserving the wellbore stability was the most critical aspect of continuous core drilling. From top to bottom, the unconsolidated sandstone in the Quaternary super stratum, the water sensitive shale in the Sifangtai group and upper stratum of the Nenjiang group, and the brittle shale of under stratum of the Nenjiang group increased the difficulty of anti-collapse drilling fluid technology. Water invasion into the shale formation often weakens the wellbore and causes problems such as wellbore collapse, shale destabilization and stuck pipe. Fluids should be designed to mitigate these shale problems. Secondly, the openhole strategy imposed the difficulty of maintaining wellbore stability in the second open process (from 245.00 m to the bottom). Finally, the total expense of the well was only one fifth of south well, which was drilled by an oilfield drilling contractor. To overcome these technical challenges, not only different drilling fluid systems such as PAM drilling fluid, DFD-LG-CMC drilling fluid and DFD-NH4HPAN-SAKH drilling fluid were adopted separately, but also technology of feasible viscosity and managed pressure drilling were used. A total of 395 trips had been run in this Cretaceous scientific drilling well and no accidents even dangerous cases occurred. The experience of CCSD-SK1 (main well) explored a successful way of employing economic drilling fluid to preceding similar scientific drilling projects in similar shale formations.

Abstract: Geotechnical prestressed anchorage structures are widely used in high slope, deep foundation pit, dam and other geotechnical reinforcement engineerings. Under the influence of the outside environment, its pretensioned force is not fixed, but presents a kind of approximate closed cyclic loading mode, under which the development and evolution regularity of the interface shear stress for the inner bond section of geotechnical prestressed anchorage structure is directly related to the ultimate bearing capacity and its long-term durability. In the experiment, the means of indoor model test was adopted, in which the different loading scheme and loading amplitude were taken into account and the interfaces mechanical properties of inner bond section for geotechnical prestressed anchorage structures under cyclic loading were studied. According to the test results, the development and evolution regularity of the interface shear strain for the inner bond section is revealed, and the long-term durability of the geotechnical anchorage bolt under cycle loading is put forward.

Abstract: A new round of upsurge of mine well construction were set off in the west area, but there are many problems, this article through the field measure of special strata freezing temperature in Bo-jiang-hai-zi coal mine airshaft, use the freezing shaft sinking security information network visualization platform that developed by Anhui University of Science and Technology, analysis several different strata, obtain the overall temperatre decline rate, and compare the difference between in-site shaft well temperature and the calculation value at different position, and difference is very small, it shows that the platform can good response the actual situation. Through calculation, the frozen wall thickness, average of frozen wall temperature, shaft well temperature are meet the engineering design requirement, so propose that in west area at the freezing method mine well construction, the main purpose is waterproof, and use single circle tube freezing can satisfy engineering design requirements.

Abstract: A new method named whole space comprehensive advanced geological forecast technique was constructed by surface spatial differential detection method combining with TSP203 system, the former can divide the distribution region, burial depth and thickness of each stratum from vertical direction clearly, and the letter can reveal the specific physical property of each stratum from horizontal direction, then combining both of them, the geological condition will be determined accurately. And then, this technique was tested and applied in a project as an example, the plan-validation results show: the formulations crossed by tunnel are full ~ strong weathered slate with rock broken zones, abundant groundwater and potential slip surface, even more, the range between crown and spandrel has irrupted into the gravel clays, all of these are unsafe for tunnel construction and suggest to have pre-supporting by 40 m Φ108 pipe shed. By comparing the results of prediction and in-situ, the whole space comprehensive advanced geological forecast scheme which avoids complexity of scheme, shortens forecasting cycle and reduces detection cost and construction interference, has encouraging forecast effect and significant popularization value.

Abstract: Ground fissure disasters are main environmental geological hazards in Xi’an. Therefore, carrying out researches on causes of cracks and mechanisms of hazard-formative, as well as setting economical and effectively countermeasures are major geological disaster puzzles to be solved.According to the key issues existing in the ground fissure researches, we use numerical simulation analysis method to solve them. Numerical simulation analysis shows that, it is reasonable that we use elastic breaking theory to describe its rupture propagation process. This paper introduces smeared crack model and explains the fracture morphology and process of sample which has microcracks inside it. Results show that such sample’s tensile strength is greatly weakened and its tensile failure is brittle fracture. Differential subsidence movement on both sides of the buried ground fissure (fault) not only leads to upwards propagation of existing cracks, whose tendency are opposite to the existing ones, but also leads to the development of nearly vertical crack belt, which is located on the uplift block and develop from top to down. Because of width of buried ground fissures’ affected zone depends on many factors, there are still lots of work to be done on the division of buried ground fissure’s deformation zone.

Abstract: Salty soil distributed widely and the engineering characteristic was complicated. The mechanical property had the relationship with spatial arrangement of soil grains, mineral component and occurrence condition of diffluent salt. The soil microstructure was an important factor to engineering characteristics. The influence of diffluent salt recrystallization on soil strength was learned according to the microstructure analysis by using environment scanning electron microscope and additional equipment X-ray energy spectrum (EDX). The influence of microstructure variation on salt soil strength was obtained by direct shear test on the salty soil before and after dehydrating. The results showed that diffluent salt recrystallization affected soil internal structure. The salty soil microstructure character was different before and after dehydrating, which changed the soil- mechanical property of salty soil.

Abstract: For the problem of serious scaling in Daqing oilfield, using XRD and SEM to detect the scale sample, investigating the influences of concentration of NaCl, KCl, Mg²⁺ and temperature on the solubility of CaCO₃, and analyzing these factors on the rule of influence on CaCO₃ scaling. According to the field test, the curve of solubility of CaCO₃ in every conditions was drawed, and study the effect of ultrasonic technique to CaCO₃ scaling. Results indicated that the scaling in oilfield is mainly CaCO₃, temperature is an important factor to affect CaCO₃ scaling, NaCl、KCl and Mg²⁺ have a certain effect on CaCO₃ solubility, and the ultrasonic can achieve the purpose of anti-scaling.

Abstract: The relative sensitivity of loess cave dwellings’ random variables is researched. The random variables are divided to resistance terms and load terms. The structural response is analyzed on standard deviation intervals with every random variable, and the gradient of structural response on each standard deviation interval is used to evaluate the sensitivity of random variables. The random variables research of loess cave dwellings in Shan city, Henan province shows that, the sensitivity of cohesion and cave leg width are the biggest, and internal friction angle and span of cave are the smallest which can be treated as constant parameters.

Abstract: Abstract. Combined the strength reduction method with ABAQUS, the development of the slope plastic strain of different reduction coefficient is obtained by constantly adjusting reduction coefficient to change the strength index of the soil. The reduction coefficient is obtained from the criterion of numerical convergence and displacement mutation and plastic zone breakthrough. Through the analysis and comparison with the results, the reduction coefficient by the criterion of displacement mutation is consistent with the result of the criterion of plastic zone breakthrough. The reduction coefficient is the safety coefficient of the slope, and compared and analyzed with the slope factor of limit equilibrium method Bishop. The result shows that the displacement mutation and the plastic zone breakthrough as criterions to judge the slope instability are reasonable.

Abstract: Based on the introduction of Artificial Neural Network principle and analyzing steps, a neural network for slop stability prediction is built in this paper. Intrinsic factors and external factors of slop stability are considered in the network, through building, training and testing the BP network model, we can see that the BP network model can analyze and determine the stability of slop; the forecasting accuracy is high and we can use it as the decision basis of slop stability analysis.