本文選題：DX嵌巖樁 + 承載特性��； 參考：《北京交通大學(xué)》2017年碩士論文

【摘要】：隨著經(jīng)濟(jì)迅速發(fā)展,現(xiàn)代化工程建設(shè)規(guī)模日益增大,對(duì)地基基礎(chǔ)提出了嚴(yán)格的要求。樁基作為常見的基礎(chǔ)形式,取得長足的進(jìn)展,向大直徑、超長、變截面等方向發(fā)展。然而,當(dāng)樁徑和樁長過大時(shí),鉆進(jìn)難度相應(yīng)增大,樁身質(zhì)量亦難以保證。三岔雙向擠擴(kuò)灌注樁(簡(jiǎn)稱DX樁)作為新樁型的代表,具有工藝先進(jìn)、施工簡(jiǎn)便和成樁可靠的特點(diǎn),能大幅度提高單樁及群樁承載力,減小樁頂沉降量,近年來廣泛應(yīng)用到超高層建筑基礎(chǔ)、大型工業(yè)建筑、LNG儲(chǔ)罐、鐵路、高速公路橋梁等基礎(chǔ)工程中。在此基礎(chǔ)上,首次采用DX嵌巖樁來替代直孔嵌巖樁,通過在強(qiáng)風(fēng)化泥質(zhì)粉沙巖層中設(shè)置承力盤,將樁端置于中風(fēng)化泥質(zhì)粉砂巖表層,在滿足承載力及沉降的要求下,減小樁徑和樁長,并成功應(yīng)用到廣東、廣西等樁基工程中,取得了良好的經(jīng)濟(jì)效益。國內(nèi)學(xué)者針對(duì)土層中DX樁承載性能作了大量分析,而DX嵌巖樁的相關(guān)研究尚屬空白。如何盡快全面探索新型DX嵌巖樁的承載機(jī)理及沉降特性,建立科學(xué)的設(shè)計(jì)方法,尤其當(dāng)前我國高速鐵路、公路、超高層建筑等工程中超長樁基越來越多,加強(qiáng)DX嵌巖樁的承載特性及失效機(jī)制的研究,成為當(dāng)前推廣應(yīng)用新型樁基結(jié)構(gòu)時(shí)工程界迫切需要解決的科學(xué)問題。為進(jìn)一步揭示DX嵌巖樁荷載傳遞特性等基本規(guī)律,本文依托于防城港鋼鐵基地原料廠項(xiàng)目,通過一系列現(xiàn)場(chǎng)試驗(yàn)、模型試驗(yàn)與數(shù)值模擬手段,對(duì)DX嵌巖樁承載特性及失效機(jī)制進(jìn)行研究,主要結(jié)論如下:(1)DX嵌巖樁Q-s曲線平緩變化,至加載末期樁頂未呈現(xiàn)明顯加速變形趨勢(shì);卸除荷載后,樁頂殘余沉降值較小,卸荷回彈量小,回彈率低,表明在強(qiáng)風(fēng)化泥質(zhì)粉砂巖層設(shè)置承力盤、樁端置于中風(fēng)化泥質(zhì)粉砂巖表層,能顯著提高單樁承載力,且DX嵌巖樁樁身壓縮性低、差異沉降小、抵抗沉降能力優(yōu)異;(2)模型試驗(yàn)表明DX嵌巖樁Q-s曲線呈緩變型,而直孔嵌巖樁在加載后期樁頂沉降急劇增加;樁徑、樁長及樁端嵌巖情況相同時(shí):DX嵌巖樁極限承載力較直孔嵌巖樁zka提高118～131%;當(dāng)直孔嵌巖樁達(dá)到承載極限時(shí),等荷載水平下DX嵌巖樁樁頂沉降較直樁zka減小80～86%;當(dāng)直孔樁zkb嵌巖深度增加(2～3d)時(shí),DX嵌巖樁承載力仍較其提高56～64%;當(dāng)直孔嵌巖樁達(dá)到承載極限時(shí),等荷載水平下DX嵌巖樁沉降值較等樁徑直樁zkb減小63～66%,充分表明DX嵌巖樁承載性能優(yōu)異、控制樁頂沉降性效果顯著;(3)DX嵌巖樁側(cè)阻力、盤阻力及端阻力同步發(fā)揮,僅需樁頂發(fā)生較小沉降:當(dāng)樁頂荷載較小時(shí),側(cè)阻力盤阻力端阻力;隨著荷載增加,側(cè)阻力、盤阻力及端阻力占總承載力百分比保持穩(wěn)定;當(dāng)荷載進(jìn)一步增大時(shí),盤阻力占總承載力百分比有所減小,端阻力所占總荷載百分比逐漸增大,端阻力盤阻力;(4)DX嵌巖樁屬于摩擦端承樁:承力盤在加載初期能有效承擔(dān)荷載,控制樁頂沉降,隨著荷載增加,盤底巖體發(fā)生局部漸進(jìn)性剪切破壞,多余荷載由樁端承擔(dān),盤阻力與端阻力占總承載力百分比呈此消彼長趨勢(shì),樁端承載力能進(jìn)一步發(fā)揮,樁身各部分協(xié)調(diào)工作,保證承載體系穩(wěn)定性;(5)承力盤底部巖體附加應(yīng)力非均勻分布,外緣處較高,由于應(yīng)力集中巖體局部剪切破裂始于此處,隨荷載增大不斷向樁根發(fā)展;樁端巖體附加應(yīng)力最大,增長速率最快,隨深度增加不斷衰減,當(dāng)盤底巖體產(chǎn)生剪切破裂帶后,樁底應(yīng)力顯著增大。(6)根據(jù)模型DX嵌巖樁Q-s曲線、承力盤底部巖體及樁底巖體附加應(yīng)力增長規(guī)律、數(shù)值模擬結(jié)果,將DX嵌巖樁失效過程分為四個(gè)階段,即:彈性階段、屈服前塑性階段、屈服后塑性階段及破壞階段。
[Abstract]:With the rapid development of economy, the construction scale of modern engineering is increasing, and the foundation of foundation is strictly required. As a common foundation form, pile foundation has made great progress, and it develops to large diameter, super long and cross section. However, when the pile diameter and pile length are too large, the difficulty of drilling is increased, and the quality of the pile is also difficult to guarantee. Three As the representative of the new type of pile, DX pile, which is a new type of pile, has the characteristics of advanced technology, simple construction and reliable pile formation. It can greatly improve the bearing capacity of single pile and pile group and reduce the settlement of pile top. In recent years, it has been widely applied to the foundation of super high-rise building, large industrial building, LNG storage tank, railway, highway bridge and other basic engineering. On this basis, the DX rock socketed pile is used for the first time to replace the straight hole rock socketed pile, and the pile end is placed on the surface of the medium weathered muddy siltstone by setting the bearing plate in the strong weathered muddy sand rock layer. The pile diameter and pile length are reduced under the requirements of bearing capacity and settlement, and the good results should be achieved in Guangdong, Guangxi and other pile foundation projects. The domestic scholars have made a great deal of analysis on the bearing capacity of the DX pile in the soil layer, and the related research on the DX rock socketed pile is still a blank. How to explore the bearing mechanism and the settlement characteristics of the new DX rock socketed pile as soon as possible, and establish a scientific design method, especially the super long Zhuang Jiyue in the high speed railway, highway and super high rise building in China In order to further reveal the basic law of the load transfer characteristics of the DX rock socketed pile, this paper relies on the project of the raw material plant of the steel base of the Fangchenggang iron and steel base, through a series of field tests, and the research on the bearing characteristics and failure mechanism of the rock socketed pile has become an urgent problem to be solved in the engineering field. The model test and numerical simulation method are used to study the bearing characteristics and failure mechanism of DX rock socketed pile. The main conclusions are as follows: (1) the Q-s curve of DX rock socketed pile is slow change, and the pile top has no obvious accelerating deformation trend at the end of loading; after unloading the load, the residual settlement value of pile top is small, the unloading rebound is small, and the rebound rate is low, indicating the strong weathering mud quality. The bearing plate of the silt rock is set, the pile end is placed on the surface of the medium weathered muddy siltstone, and the bearing capacity of the single pile can be improved significantly. And the DX rock socketed pile body has low compressibility, small difference settlement, and excellent resistance to settlement. (2) the model test shows that the Q-s curve of the DX rock socketed pile is slowly variable, and the vertical hole rock socketed pile increases sharply in the later stage of the pile, pile diameter and pile. At the same time, the ultimate bearing capacity of DX rock socketed pile is increased by 118 ~ 131% than that of straight hole rock socketed pile zka; when the vertical hole rock socketed pile reaches the bearing limit, the settlement of the pile top settlement of the DX rock socketed pile is 80 to 86% lower than that of the straight pile under the same load level; when the zkb rock socketed depth increases (2 to 3D), the bearing capacity of the DX rock socketed pile is still higher than that of 56 to 64%; when the zkb rock socketed pile is increased by 56 to 64%. When the vertical hole rock socketed pile reaches the bearing limit, the settlement value of DX rock socketed pile under equal load is reduced by 63 to 66% than that of the same pile zkb, which fully indicates that the bearing performance of the DX rock socketed pile is excellent, and the settlement effect of the pile top is remarkable. (3) the side resistance of the rock pile, the disc resistance and the end resistance are synchronous, only the small settlement of the pile top is needed, when the pile top load is small When the load increases, the percentage of the total bearing capacity decreases as the load increases. When the load is further increased, the percentage of the total bearing capacity decreases, the total load percentage of the end resistance increases gradually and the end resistance disk resistance; (4) DX rock socketed pile belongs to the friction end bearing pile: bearing pile. At the initial stage of loading, the force can be effectively loaded and the settlement of the pile top is controlled. With the increase of load, the rock mass in the bottom is partially progressive shear failure. The excess load is assumed by the pile end, the disc resistance and the end resistance account for the percentage of the total bearing capacity, and the bearing capacity of the pile ends can be brought into play in one step, and the pile body parts coordinate work and guarantee the bearing body. (5) the additional stress in the bottom rock mass of the bearing plate is nonuniform distribution, the outer edge is higher, because the local shear fracture of the stress concentration rock begins to develop with the load increasing. The maximum additional stress of the rock mass, the fastest increase rate and the constant attenuation with the depth, when the rock bottom rock produces the shear fracture zone, the pile bottom The stress increases significantly. (6) according to the Q-s curve of the model DX rock socketed pile, the additional stress growth law of the bottom rock mass and the bottom rock mass of the bearing disc, the failure process of the DX rock socketed pile is divided into four stages, that is, the elastic stage, the pre yield plastic stage, the post yield plastic stage and the failure stage.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU473.1

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 張德華;郭鵬;賀德新;;DX嵌巖樁承載特性現(xiàn)場(chǎng)試驗(yàn)研究[J];地下空間與工程學(xué)報(bào);2016年S2期

2 張德華;胡鋒;陳文博;徐f，

本文編號(hào)：2106364