带水施工对土钉抗拔力影响的模型试验研究

发布时间：2018-03-29 22:16

本文选题：膨胀土　切入点：带水施工　出处：《合肥工业大学》2017年硕士论文

【摘要】：随着城市的发展,由于地面空间有限,目前正在大力开发地下空间。地下空间开发的过程中,会涉及对基坑的支护。其中,土钉支护技术因其具有施工快速、简便等优点,成为了基坑支护的重要方法之一。土钉成孔方式分为干法成孔和带水成孔两种形式。合肥地区(分布着膨胀土)土钉支护的施工,一般采用干法成孔施工土钉,但在实际施工过程中,为达到防止成孔过程中孔壁的坍塌的目的,会存在带水成孔方式施工土钉的情况。然而,膨胀土具有吸水膨胀和失水收缩的特性,采用带水方式成孔施工土钉,会使膨胀土受到水的浸泡作用,而导致膨胀土的强度衰减,影响土钉的抗拔力。目前,对于合肥地区,土钉采用带水成孔施工对其抗拔力影响情况,进行的相关试验研究较少。因此,本文采用模型试验的方法研究带水施工对土钉的抗拔力的影响,为合肥地区土钉支护结构的涉水施工,提供参考意义。(1)试验将环刀内土样去除一半后,对其内表面不浸泡及带水浸泡1、2、4、6、12、24小时,然后注浆制作接触面直剪试样,养护3天,进行剪切试验,测试土钉锚固体与膨胀土接触面的粘结强度变化情况。由试验结果可知,土钉锚固体与膨胀土接触面受水浸泡后,含水量增大,强度产生衰减,其衰减幅度随着浸泡时间的延长逐渐减缓。(2)室内模拟土钉的干法成孔和带水成孔两种方式,带水成孔即分别向孔内注满水浸泡1、2、4、6、12、24小时,然后插入土钉注浆制作土钉室内模型,养护3天,进行拉拔试验,测试土钉的极限抗拔力。试验结果显示,随着浸泡时间的延长,土钉的极限抗拔力减小,其减小趋势表现为前6小时速度快,6-24小时速度减慢。(3)基于室内土钉模型拉拔试验的数据,依据单根土钉的抗拔力计算公式,对二者界面的黏聚力值进行反算,并与通过直剪试验测得的二者界面的黏聚力值进行对比分析。根据对比结果可知,黏聚力反算值与实验值差值不大,故可考虑采用直剪试验测试土钉锚固体与膨胀土接触面受水浸泡后的强度,为合肥地区土钉带水施工抗拔力计算,提供数据依据,也可为其他膨胀土地区土钉类似问题提供借鉴。
[Abstract]:With the development of the city, because of the limited ground space, the underground space is being developed vigorously. In the process of the underground space development, the foundation pit support will be involved. Among them, the soil nailing support technology has the advantages of quick construction and simple construction, etc. Soil nailing has become one of the important methods of foundation pit support. Soil nailing is divided into dry hole formation and water drilling. Soil nailing in Hefei area (distributed expansive soil) is generally constructed by dry-hole construction. However, in order to prevent the hole wall from collapsing in the process of actual construction, there will be the case of soil nailing in the way of hole formation with water. However, the expansive soil has the characteristics of water absorption and shrinkage. When soil nailing is constructed by taking water into a hole, the expansive soil will be soaked in water, which will lead to the strength attenuation of expansive soil, which will affect the pullout strength of soil nailing. At present, for the Hefei area, the strength of the soil nailing will be decreased. The influence of soil nailing construction with water on its pullout resistance is less. Therefore, the model test method is used to study the effect of soil nailing construction on soil nailing's pullout capacity, and the influence of soil nailing construction on the pullout resistance of soil-nailing is studied in this paper. For the construction of soil nailing support structure in Hefei area, the reference significance is provided. 1) after the soil sample in the ring knife is half removed, the internal surface of the soil sample is not soaked and the water is taken to soak the soil sample for 24 hours. Then the direct shear specimen of the contact surface is made by grouting, and the sample is maintained for 3 days. Shear test was carried out to test the change of bond strength between soil nailing anchors and expansive soil. From the test results, the water content increases and the strength attenuates when the contact surface of soil nailing anchors and expansive soil is soaked in water. With the prolongation of soaking time, the attenuation range of soil nailing decreases gradually. (2) the dry-made holes and water-filled holes of indoor simulated soil nailing are dry-formed and water-filled, I. e., water filled holes are injected into the holes for 24 hours respectively, and then soil nailing grouting is inserted to make the indoor model of soil nailing. After 3 days of curing, the ultimate pullout strength of soil nailing was tested. The results showed that the ultimate pullout strength of soil nailing decreased with the prolongation of soaking time. The decreasing trend is as follows: the speed of the first 6 hours is fast and the speed of 6-24 hours is slowing down. (3) based on the data of the model drawing test of indoor soil nailing, the cohesion of the two interface is calculated back according to the formula of the pullout force of the single soil nailing. And compared with the cohesion value of the two interface measured by direct shear test. According to the comparison results, the difference between the back calculation value of cohesion force and the experimental value is not big. Therefore, direct shear test can be used to test the strength of soil nailing and expansive soil contact surface after soaking in water, which can provide data basis for calculation of pullout strength of soil nailing construction with water in Hefei area. It can also be used for reference for similar problems of soil nailing in other expansive soil areas.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU753

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