本文選題：預(yù)應(yīng)力錨索復(fù)合土釘支護(hù)　切入點(diǎn)：砂卵石地層　出處：《中國(guó)地質(zhì)大學(xué)（北京）》2014年博士論文

【摘要】：基于土釘支護(hù)技術(shù)而發(fā)展起來的預(yù)應(yīng)力錨索復(fù)合土釘支護(hù)技術(shù)充分結(jié)合了土釘支護(hù)技術(shù)和預(yù)應(yīng)力錨索支護(hù)技術(shù)的優(yōu)點(diǎn)，已在基坑支護(hù)工程中得到廣泛應(yīng)用。但是目前該技術(shù)多應(yīng)用于粉土、粘土等粘性土地層，而在砂卵石地層中的應(yīng)用和研究則相對(duì)較少，理論明顯滯后于工程實(shí)踐。為此，論文針對(duì)這一問題進(jìn)行了較為深入的研究，所開展的主要工作及研究成果如下： （1）在對(duì)典型工程實(shí)例進(jìn)行分析的基礎(chǔ)上，采用理論分析、現(xiàn)場(chǎng)試驗(yàn)和監(jiān)測(cè)及數(shù)值模擬等多種方法對(duì)砂卵石地層中的預(yù)應(yīng)力錨索復(fù)合土釘支護(hù)技術(shù)設(shè)計(jì)理論及方法進(jìn)行了全面而深入的研究。認(rèn)為在砂卵石地層中進(jìn)行基坑預(yù)應(yīng)力錨索復(fù)合土釘支護(hù)設(shè)計(jì)時(shí)應(yīng)對(duì)砂卵石地層取非零的粘聚力（或結(jié)構(gòu)力），這樣不但可以大大減小支護(hù)工程量，而且亦能保證施工安全。 （2）基于莫爾-庫(kù)侖強(qiáng)度理論討論了砂卵石地層的抗剪強(qiáng)度，認(rèn)為對(duì)于砂卵石地層，其固有的結(jié)構(gòu)力（咬合力）及摩阻角是描述其抗剪強(qiáng)度的重要參數(shù)，應(yīng)該且必須在設(shè)計(jì)中予以考慮。同時(shí)通過現(xiàn)場(chǎng)直剪試驗(yàn)，對(duì)砂卵石地層強(qiáng)度參數(shù)進(jìn)行了原位測(cè)試，認(rèn)為砂卵石地層的粘聚力與其在天然狀態(tài)下的密實(shí)度、結(jié)構(gòu)性等密切相關(guān)，建議取為3~10kPa。 （3）基于土釘支護(hù)設(shè)計(jì)中的土體準(zhǔn)粘聚力理論，認(rèn)為由于土釘支護(hù)而形成的復(fù)合土體，其粘聚力較原位土體將會(huì)有所增加，并推導(dǎo)了相應(yīng)的準(zhǔn)粘聚力計(jì)算公式。 （4）采用FLAC3D數(shù)值方法對(duì)砂卵石地層中預(yù)應(yīng)力錨索復(fù)合土釘支護(hù)機(jī)理進(jìn)行了研究，，認(rèn)為砂卵石地層的粘聚力對(duì)基坑邊坡位移有重要影響，隨著砂卵石地層粘聚力的增加，基坑邊坡土體位移迅速減小。預(yù)應(yīng)力錨索的施加可以明顯改善土釘受力，減小基坑邊坡位移。 （5）通過對(duì)砂卵石地層基坑工程中的土釘、錨索內(nèi)力的現(xiàn)場(chǎng)監(jiān)測(cè)結(jié)果表明：土釘及錨索受力都出現(xiàn)沿其長(zhǎng)度先增大后減小的趨勢(shì)，且隨著基坑開挖深度的增加，其受力亦出現(xiàn)先增大而后減小的現(xiàn)象。同時(shí)對(duì)比分析了砂卵石地層粘聚力取零與非零兩種情況下的設(shè)計(jì)與計(jì)算結(jié)果，表明當(dāng)取粘聚力為非零值時(shí)，實(shí)際監(jiān)測(cè)結(jié)果與計(jì)算結(jié)果更為接近，從而說明了在砂卵石地層中粘聚力取非零值的合理性。 （6）以實(shí)際基坑工程為背景，采用數(shù)值試驗(yàn)的方法討論了砂卵石地層粘聚力取值大小對(duì)基坑邊坡土體位移、錨索及土釘受力和土體塑性區(qū)的影響。結(jié)果表明隨著砂卵石地層粘聚力的增加，基坑邊坡土體位移及支護(hù)結(jié)構(gòu)受力明顯減小，但其減小幅度隨粘聚力的增加而逐漸變緩。
[Abstract]:Based on the soil nailing technology, the prestressed anchor cable composite soil nailing support technology combines the advantages of soil nailing support technology and prestressed anchor cable support technology. It has been widely used in foundation pit support engineering. But at present, the technology is mostly used in clay and silt layer, but the application and research in sandy pebble stratum is relatively few, and the theory is obviously lagging behind the engineering practice. The thesis has carried on the thorough research to this question, has carried on the main work and the research result as follows:. 1) based on the analysis of typical engineering examples, theoretical analysis is adopted. The design theory and method of prestressed anchor cable composite soil nailing supporting technology in sandy pebble stratum are studied comprehensively and deeply by field test, monitoring and numerical simulation. It is considered that foundation pit is carried out in sand pebble stratum. In the design of composite soil nailing with prestressed anchor cable, the cohesive force (or structural force) of sand pebble stratum should be taken as non-zero, which not only can greatly reduce the amount of support engineering, And can also ensure construction safety. (2) based on Mohr-Coulomb strength theory, the shear strength of sand pebble formation is discussed. It is considered that the inherent structural force (bite force) and friction angle are important parameters to describe the shear strength of sand pebble formation. It should and must be taken into account in the design. At the same time, the in-situ testing of the strength parameters of the sand pebble formation is carried out through direct shear tests in the field. It is considered that the cohesion of the sand gravel formation is closely related to its density and structure in the natural state. It is suggested to be 3 / 10 KPA. 3) based on the theory of quasi-cohesive force of soil in soil nailing design, it is considered that the cohesive force of composite soil formed by soil nailing support will be increased compared with that of in-situ soil, and the corresponding formula for calculating quasi-cohesive force is derived. The FLAC3D numerical method is used to study the mechanism of prestressed anchor cable composite soil nailing support in sand pebble strata. It is considered that the cohesive force of sand gravel stratum has an important effect on the displacement of foundation pit slope, and with the increase of cohesion force of sand pebble stratum, the soil nailing support mechanism of prestressed Anchorage cable in sand pebble formation is studied. The soil displacement of excavation slope decreases rapidly, and the application of prestressed anchor cable can obviously improve the stress of soil nailing and reduce the displacement of slope of foundation pit. The field monitoring results of the internal force of anchor cable in sand pebble foundation pit show that the stress of soil nailing and anchor cable increases first and then decreases along with the length of soil nailing, and increases with the increase of excavation depth of foundation pit. At the same time, the design and calculation results of the cohesive force of sand and pebble strata with zero and non-zero are compared and analyzed. It is shown that when the cohesive force is taken as non-zero, The actual monitoring results are closer to the calculated results, which shows the rationality of the non-zero cohesive force in the sandy pebble formation. (6) based on the actual foundation pit engineering, the numerical test method is used to discuss the influence of the cohesion of sand and pebble stratum on the displacement of the soil mass of the foundation pit slope. The results show that the displacement of soil mass and the force of supporting structure decrease obviously with the increase of cohesive force of sand pebble stratum, but the decrease range of soil displacement decreases gradually with the increase of cohesive force.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)（北京）
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU753

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