本文選題：膨脹土　切入點(diǎn)：帶水施工　出處：《合肥工業(yè)大學(xué)》2017年碩士論文

【摘要】：隨著城市的發(fā)展,由于地面空間有限,目前正在大力開發(fā)地下空間。地下空間開發(fā)的過(guò)程中,會(huì)涉及對(duì)基坑的支護(hù)。其中,土釘支護(hù)技術(shù)因其具有施工快速、簡(jiǎn)便等優(yōu)點(diǎn),成為了基坑支護(hù)的重要方法之一。土釘成孔方式分為干法成孔和帶水成孔兩種形式。合肥地區(qū)(分布著膨脹土)土釘支護(hù)的施工,一般采用干法成孔施工土釘,但在實(shí)際施工過(guò)程中,為達(dá)到防止成孔過(guò)程中孔壁的坍塌的目的,會(huì)存在帶水成孔方式施工土釘?shù)那闆r。然而,膨脹土具有吸水膨脹和失水收縮的特性,采用帶水方式成孔施工土釘,會(huì)使膨脹土受到水的浸泡作用,而導(dǎo)致膨脹土的強(qiáng)度衰減,影響土釘?shù)目拱瘟�。目�?對(duì)于合肥地區(qū),土釘采用帶水成孔施工對(duì)其抗拔力影響情況,進(jìn)行的相關(guān)試驗(yàn)研究較少。因此,本文采用模型試驗(yàn)的方法研究帶水施工對(duì)土釘?shù)目拱瘟Φ挠绊?為合肥地區(qū)土釘支護(hù)結(jié)構(gòu)的涉水施工,提供參考意義。(1)試驗(yàn)將環(huán)刀內(nèi)土樣去除一半后,對(duì)其內(nèi)表面不浸泡及帶水浸泡1、2、4、6、12、24小時(shí),然后注漿制作接觸面直剪試樣,養(yǎng)護(hù)3天,進(jìn)行剪切試驗(yàn),測(cè)試土釘錨固體與膨脹土接觸面的粘結(jié)強(qiáng)度變化情況。由試驗(yàn)結(jié)果可知,土釘錨固體與膨脹土接觸面受水浸泡后,含水量增大,強(qiáng)度產(chǎn)生衰減,其衰減幅度隨著浸泡時(shí)間的延長(zhǎng)逐漸減緩。(2)室內(nèi)模擬土釘?shù)母煞ǔ煽缀蛶煽變煞N方式,帶水成孔即分別向孔內(nèi)注滿水浸泡1、2、4、6、12、24小時(shí),然后插入土釘注漿制作土釘室內(nèi)模型,養(yǎng)護(hù)3天,進(jìn)行拉拔試驗(yàn),測(cè)試土釘?shù)臉O限抗拔力。試驗(yàn)結(jié)果顯示,隨著浸泡時(shí)間的延長(zhǎng),土釘?shù)臉O限抗拔力減小,其減小趨勢(shì)表現(xiàn)為前6小時(shí)速度快,6-24小時(shí)速度減慢。(3)基于室內(nèi)土釘模型拉拔試驗(yàn)的數(shù)據(jù),依據(jù)單根土釘?shù)目拱瘟τ?jì)算公式,對(duì)二者界面的黏聚力值進(jìn)行反算,并與通過(guò)直剪試驗(yàn)測(cè)得的二者界面的黏聚力值進(jìn)行對(duì)比分析。根據(jù)對(duì)比結(jié)果可知,黏聚力反算值與實(shí)驗(yàn)值差值不大,故可考慮采用直剪試驗(yàn)測(cè)試土釘錨固體與膨脹土接觸面受水浸泡后的強(qiáng)度,為合肥地區(qū)土釘帶水施工抗拔力計(jì)算,提供數(shù)據(jù)依據(jù),也可為其他膨脹土地區(qū)土釘類似問(wèn)題提供借鑒。
[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.
【學(xué)位授予單位】：合肥工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU753

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