【摘要】：實(shí)際工程中,淺基礎(chǔ)形式中應(yīng)用比較廣泛的是條形基礎(chǔ)。對(duì)于條形基礎(chǔ)作用下的地基承載力,可以比較方便地把其當(dāng)作平面應(yīng)變問(wèn)題來(lái)解決。本文主要研究十字交叉條形荷載作用下的地基承載力。由于十字交叉條形荷載作用下的地基承載力是一個(gè)三維問(wèn)題,平面應(yīng)變分析已不能反映其破壞特性。目前對(duì)于十字交叉條形基礎(chǔ)的研究相對(duì)較少,導(dǎo)致在承載力設(shè)計(jì)上偏于保守,造成了材料和承載力的浪費(fèi),所以有必要對(duì)其承載力規(guī)律做一定研究,以便更好的指導(dǎo)實(shí)際工程。對(duì)于十字交叉條形基礎(chǔ)表面的荷載分布,本文假定用均布荷載代替作用在基礎(chǔ)交叉點(diǎn)處的集中荷載。本文運(yùn)用FLAC3D對(duì)不同形式荷載作用下地基的承載力、地基應(yīng)力分布規(guī)律、地基的破壞模式和變形機(jī)理等進(jìn)行了全面的研究,可得到以下主要結(jié)論:(1)“口”字形荷載、“田”字形荷載和“九宮格”形荷載作用下的地基承載力均隨著內(nèi)摩擦角的增大呈現(xiàn)遞增的趨勢(shì)。當(dāng)內(nèi)摩擦角不變時(shí),“口”字形荷載、“田”字形荷載和“九宮格”形荷載作用下的地基承載力呈現(xiàn)增大的趨勢(shì)。對(duì)于“口”字形荷載,地基破壞時(shí),地基隆起量在荷載內(nèi)外側(cè)基本相等;對(duì)于“田”字形荷載和“九宮格”形荷載,地基發(fā)生破壞時(shí),地基隆起量荷載外側(cè)大于內(nèi)側(cè)。(2)對(duì)于“口”字形荷載,長(zhǎng)寬比對(duì)承載力有一定影響。在一定長(zhǎng)寬比范圍內(nèi),地基承載力隨著長(zhǎng)寬比的增加呈現(xiàn)先增大后減小的趨勢(shì)。通過(guò)數(shù)值模擬,不同長(zhǎng)寬比下,地基承載力最多提高了11.4%。(3)“口”字形荷載長(zhǎng)寬比為1時(shí),在一定范圍內(nèi),地基承載力隨著荷載邊長(zhǎng)的減小呈現(xiàn)遞增的趨勢(shì)。通過(guò)數(shù)值模擬,長(zhǎng)寬比為1時(shí),地基承載力最多提高了15.7%。(4)在不同的長(zhǎng)寬比作用下,剪應(yīng)變率云圖在長(zhǎng)邊下方開(kāi)展深度大于短邊下方開(kāi)展深度,長(zhǎng)寬比越大,其開(kāi)展深度相差越大。由于“口”字形荷載間的相互影響,荷載外側(cè)剪應(yīng)變率包絡(luò)線全部延伸至地基表面,在荷載內(nèi)側(cè)剪應(yīng)變率包絡(luò)線未全部延伸至地基表面。此時(shí)地基破壞模式類似于整體剪切破壞,只是破壞曲線不再關(guān)于荷載中心對(duì)稱�！翱凇弊中魏奢d長(zhǎng)寬比為1,邊長(zhǎng)小于2m時(shí),地基承載力受邊長(zhǎng)影響較大;邊長(zhǎng)大于3m時(shí),地基承載力受邊長(zhǎng)影響較小。
[Abstract]:In practical engineering, strip foundation is widely used in shallow foundation form. The bearing capacity of the foundation under the action of strip foundation can be easily solved as a plane strain problem. This paper mainly studies the bearing capacity of foundation under cross-cross strip load. Because the bearing capacity of foundation under cross strip load is a three dimensional problem, the plane strain analysis can no longer reflect its failure characteristics. At present, the research of cross strip foundation is relatively few, which leads to conservative design of bearing capacity and waste of materials and bearing capacity. So it is necessary to do some research on the bearing capacity of cross strip foundation in order to better guide the practical engineering. For the load distribution on the cross strip foundation surface, it is assumed that uniform load is used instead of the concentrated load acting at the intersection of the foundation. In this paper, FLAC3D is used to study the bearing capacity, stress distribution, failure mode and deformation mechanism of foundation under different forms of load. The main conclusions are as follows: (1) "mouth" zigzag load, The bearing capacity of foundation under the action of "Tian" zigzag load and "Jiugong lattice" load is increasing with the increase of internal friction angle. When the angle of internal friction is constant, the bearing capacity of foundation under the action of "mouth", "Tian" and "Jiugong" is increasing. For the "mouth" zigzag load, when the foundation is damaged, the uplift of the foundation is basically equal to the inside and outside of the load; for the "Tian" zigzag load and the "Jiugong lattice" load, the foundation is destroyed, The lateral load of foundation uplift is larger than that of inner side. (2) for "mouth" zigzag load, the ratio of length to width has a certain influence on the bearing capacity. In a certain range of aspect ratio, the bearing capacity of foundation increases first and then decreases with the increase of aspect ratio. Through numerical simulation, the bearing capacity of foundation is increased by 11.44.The maximum value of bearing capacity is increased by 11.4under different aspect ratio. (3) when the ratio of length to width of the zigzag load is 1, the bearing capacity of the foundation increases with the decrease of load side length in a certain range. Through numerical simulation, when the aspect ratio is 1, the bearing capacity of the foundation increases by 15.7. (4) under the action of different aspect ratio, the depth of shear strain rate cloud map is greater than that of the bottom of the short edge, and the ratio of length to width increases. The greater the depth of its development. Due to the interaction between the "mouth" and zigzag loads, the lateral shear strain rate envelope of the load extends to the surface of the foundation, while the envelope of the shear strain rate on the inner side of the load does not extend to the surface of the foundation. The failure mode of the foundation is similar to that of the whole shear failure, except that the failure curve is no longer symmetrical to the center of the load. When the ratio of length to width is 1 and the side length is less than 2m, the bearing capacity of the foundation is greatly affected by the side length, and the bearing capacity of the foundation is less affected by the side length when the side length is more than 3m.
【學(xué)位授予單位】：南昌航空大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU470

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