模拟月壤土拱效应试验研究与三维离散元模拟

发布时间：2018-02-02 13:18

本文关键词： 模拟月壤土拱效应三维离散元 PFC3D　出处：《中国地质大学（北京）》2010年硕士论文　论文类型：学位论文

【摘要】： 当前,人类面临煤炭、石油和天然气等现有传统能源日益枯竭的局面。于是,人们将目光投向了拥有丰富资源的月球。为了开发和利用月球资源,美国、俄罗斯等国家兴起新一轮世界性的“重返月球”热潮。中国也制定了探月工程“三步走”的计划,其中第三步以及未来月球基地的建设过程中,必将涉及到月壤原位勘察测试取样。为了确保在月球上顺利而完整的实现原位取样,先期必须在地球上进行相关的模拟试验。根据地球上原位取样的经验,经常会遇到取土器钻进后,土样采取率达不到要求,甚至是根本取不到土样的情况。通过对有关土力学机理的分析,很可能是在钻进的过程中受到了土拱效应的影响。本文首先选用与月壤样品具有相似矿物化学组成的火山喷发物质-靖宇火山灰作为制备模拟月壤原物质,制得火山灰试样。并对火山灰试样进行基本物理力学性质试验。结果表明:用雷蒙磨粉碎、并过0.5mm筛的火山灰试样及其与金刚砂的配合物,颗粒形状与月壤相似,土粒比重略小于典型月壤的土粒比重,平均粒径与内摩擦角跟月壤接近,可以用来模拟月壤。然后通过模拟月壤土拱效应验证试验表明:在模拟月壤中很容易出现土拱现象,并且形成土拱的难易程度与取样圆管孔径、模拟月壤的相对密度有关。总体来说:相同孔径时,相对密度越大,越容易成拱;相同密实度时,孔径越小,越容易成拱,且密实度较大时成拱高度约为孔的半径。通过土拱效应对原位取样影响的试验研究从机理上解释了可能造成原位取样失败的原因:受土拱作用的影响,土拱以下的土样被挡在管外,较难进入试验管中。同时,已进入管中的土样在试验管下压过程中因为土拱的影响会变得较松散,致使土样与管壁的摩擦力不足以在提取试验管时将土样取出,从而造成了钻取原状土样时的失败。最后运用三维离散元软件PFC3D模拟压管试验表明,圆柱墙在下压的过程中,土体中出现了明显的土拱现象。本文研究表明,在进行原位取样的过程中非常容易产生土拱效应。特别是月壤取样时,为了确保原位取样的顺利完成,更应该加强对土拱效应的研究。
[Abstract]:At present, mankind is faced with the situation that coal, oil and natural gas and other existing traditional energy are increasingly exhausted. Therefore, people have turned their eyes to the moon, which is rich in resources. In order to develop and utilize the lunar resources, the United States. Russia and other countries have a new round of worldwide "return to the moon" upsurge. China has also formulated a "three-step" plan for lunar exploration, the third of which is in the process of building a future lunar base. In order to ensure the successful and complete in situ sampling on the moon, the related simulation tests must be carried out on the earth in advance. According to the experience of in situ sampling on the earth. It is often encountered that the rate of soil sample can not reach the requirement, even the soil sample can not be obtained, after drilling with a soil collector, the mechanism of soil mechanics is analyzed. It is very likely that the soil arch effect affected the drilling process. In this paper, the volcanic eruption material, Jingyu volcanic ash, which has similar mineral chemical composition to the lunar soil sample, is first selected as the raw material of the simulated lunar soil. The basic physical and mechanical properties of the pozzolanic sample were tested. The results showed that the ash sample and its complex with Emery were comminuted by Ramon mill and passed 0.5mm sieve. The particle shape is similar to that of the lunar soil, the specific gravity of the soil is slightly smaller than that of the typical lunar soil, and the average particle size and the angle of internal friction are close to the lunar soil, which can be used to simulate the lunar soil. Then through the simulation of the lunar soil arch effect verification test shows that the soil arch phenomenon is easy to occur in the simulated lunar soil and it is easy to form the soil arch and the pore diameter of the sampling pipe. The relative density of the simulated lunar soil is related to the relative density of the lunar soil. On the whole, the higher the relative density of the lunar soil is, the easier it is to form arch with the same pore diameter. At the same compactness, the smaller the aperture, the easier it is to form arch, and the higher the density, the higher the arch height is about the radius of the hole. Through the experimental study on the effect of soil arch effect on in-situ sampling, the possible reasons for failure of in-situ sampling are explained from the mechanism: under the influence of soil arch, the soil samples below the soil arch are blocked out of the pipe. It is more difficult to enter the test tube. At the same time, the soil sample already in the pipe will become looser because of the influence of the soil arch during the compression process of the test tube, so the friction between the soil sample and the pipe wall is not enough to remove the soil sample from the test tube when it is extracted. As a result, the failure of drilling for the original soil sample is caused. In the end, the results of three dimensional discrete element software PFC3D show that the soil arch appears in the soil during the compression process of the cylindrical wall. In this paper, it is shown that the soil arch effect is very easy to occur in the process of in-situ sampling, especially in the case of lunar soil sampling, in order to ensure the successful completion of in-situ sampling, the study of soil arch effect should be strengthened.
【学位授予单位】：中国地质大学（北京）
【学位级别】：硕士
【学位授予年份】：2010
【分类号】：P184

【引证文献】