本文選題：深基坑工程　切入點(diǎn)：滲流　出處：《太原理工大學(xué)》2013年博士論文　論文類型：學(xué)位論文

【摘要】：在地下水位較高的場(chǎng)地進(jìn)行深基坑工程的設(shè)計(jì)及施工,降水開挖引起局部水文地質(zhì)條件的變化與支護(hù)結(jié)構(gòu)及周邊環(huán)境之間是相互制約、相互作用的。 本文首先對(duì)太原市汾河低階地地層進(jìn)行了分類整理,按照地層變化規(guī)律、粒徑組成、滲透性質(zhì)及帷幕底部可能嵌固進(jìn)入地層透水性質(zhì)的不同,將基坑止水帷幕分為三類嵌固模式。每種模式給出了相應(yīng)的滲流變化特征及其對(duì)支護(hù)結(jié)構(gòu)及地面變形的影響程度。 本文對(duì)太原市中環(huán)壹號(hào)深基坑工程監(jiān)測(cè)資料進(jìn)行整理分析,依此為模擬基礎(chǔ),以比奧固結(jié)理論為基礎(chǔ)利用Flac3D的cysoil模型進(jìn)行數(shù)值模擬,深入研究了止水帷幕為第二類嵌固模式時(shí),水頭邊界條件下分別采用側(cè)向和上部?jī)煞N不同水頭補(bǔ)給位置時(shí),降水回灌四種組合方式的滲流條件與支護(hù)結(jié)構(gòu)及地面變形之間的相互作用；并對(duì)地下水位改變、土體性質(zhì)改變、滲透系數(shù)改變、回灌條件改變引起基坑周邊地面沉降的影響規(guī)律進(jìn)行了分析研究。 最后對(duì)滲透系數(shù)與降水前后土體的力學(xué)性質(zhì)測(cè)試的試驗(yàn)方法及參數(shù)的變化規(guī)律進(jìn)行了深入的分析研究。 通過以上分析研究獲得的主要認(rèn)識(shí)及結(jié)論為： 1、材料本構(gòu)關(guān)系cysoil模型是摩爾-庫(kù)侖的衍生模型,采用定律為增量彈性法則、破壞準(zhǔn)則和流動(dòng)準(zhǔn)則。運(yùn)用該模型將降水回灌的滲流變化與土力學(xué)有機(jī)地組合起來,與比奧固結(jié)理論相結(jié)合能很好反映地下水的滲流特征及開挖應(yīng)力改變之間的作用。模擬結(jié)果與中環(huán)壹號(hào)監(jiān)測(cè)資料對(duì)比,地面沉降的模擬吻合率高達(dá)90%以上,地下連續(xù)墻墻體水平位移的吻合率為60%-80%,水平支撐的撐力吻合率達(dá)80%以上,說明該模型適用于本論文研究的基坑開挖降水工程。 2、通過對(duì)各項(xiàng)水文參數(shù)改變的模擬得出： 1)水頭邊界條件的側(cè)向固定水頭補(bǔ)給位置適用于第一類、第二類嵌固模式,上部固定水頭補(bǔ)給位置適用于第三類嵌固模式。 2)分步降水加回灌的降水開挖工況對(duì)基坑周邊地面變形控制最為有利�；毓嗍强刂频孛娉两档挠行侄�,回灌井位置在基坑開挖深度(0.5～1.0)H范圍內(nèi)最佳。 3)根據(jù)正交水平原理提供了回灌井深度、回灌壓力、回灌井?dāng)?shù)量及排數(shù)、帷幕深度各因素及因素組合對(duì)地面沉降的貢獻(xiàn)系數(shù)表,來評(píng)價(jià)各參數(shù)及參數(shù)組合對(duì)地面沉降的影響程度,以便設(shè)計(jì)施工中采用最優(yōu)最經(jīng)濟(jì)的回灌組合方式。 4)降水引起基坑外地面沉降曲線為“凹”形：從基坑邊至最大沉降點(diǎn)處為對(duì)數(shù)曲線,從最大沉降點(diǎn)至降水影響范圍的最外邊界處為線性關(guān)系。利用回歸關(guān)系給出第二類嵌固模式下基坑外地面變形與滲透系數(shù)變化關(guān)系的計(jì)算公式。 5)考慮回灌滲流應(yīng)力場(chǎng)作用比不考慮滲流作用,地表沉降降低50%,坑底隆起增35%,支護(hù)結(jié)構(gòu)的水平位移增加30%,水平支撐軸力增加15%。設(shè)計(jì)中需考慮回灌滲流作用,以降低支護(hù)結(jié)構(gòu)的風(fēng)險(xiǎn)。 6)墻體水平位移受水平側(cè)向支撐的限制,同一斷面出現(xiàn)兩頭小中間大的鼓肚子撓曲形狀。墻體的最大水平位移位置在墻頂下0.85H處,在開挖深度(0.4-0.85)H水平位移增量大,該段落為支護(hù)結(jié)構(gòu)的最薄弱部位,是設(shè)置支撐及施工監(jiān)測(cè)的重點(diǎn)部位。 7)地表沉降量隨著土體彈性模量的增大而減��；地表最大沉降和彈性模量曲線大致呈折線形分布。隨著土體模量的提高,土體變形滑移面的斜率在增大,滑移面越來越陡,土體的變形影響范圍在減小。但土體模量的提高對(duì)支護(hù)結(jié)構(gòu)的變形影響不大。 3、對(duì)水文參數(shù)的試驗(yàn)研究得出： 1)綜合考慮取樣過程中土樣的擾動(dòng)程度、取土深度、土樣應(yīng)力釋放情況、孔隙水壓力消散程度及滲透系數(shù)對(duì)土層影響的權(quán)重等因素,提出對(duì)室內(nèi)試驗(yàn)測(cè)出的滲透系數(shù)的修正公式。 2)降水過程相當(dāng)于給土體一個(gè)預(yù)壓加固作用,降水后土體壓縮模量ES1-2增大25%；粘聚力增大33%；內(nèi)摩擦角增大8%。 3)高壓固結(jié)多級(jí)卸荷回彈試驗(yàn)土體均出現(xiàn)“回滯圈”,卸荷曲線的斜率不一致,但回彈的路徑幾乎是一組平行線。 本文的研究成果是對(duì)太原市中環(huán)壹號(hào)工程的支護(hù)體系研究中得出的,對(duì)水位較高的河流一級(jí)階地基坑開挖的設(shè)計(jì)及施工具有一定的借鑒和指導(dǎo)作用,對(duì)深大基坑中滲流場(chǎng)與支護(hù)結(jié)構(gòu)、周邊環(huán)境的相互作用理論的研究具有一定的意義。
[Abstract]:In the design and construction of deep foundation pit at high groundwater level, the change of local hydrogeological conditions caused by precipitation and excavation is interdependent and interacted with supporting structure and surrounding environment.
This paper firstly classified the Fenhe River in Taiyuan city low terrace formation, in accordance with the law of change of formation, particle size composition, permeability properties and may be fixed at the bottom of the curtain into the formation permeability is different, the waterproof curtain is divided into three types of embedded mode. Each mode is given and the corresponding variation of seepage on supporting the structure and the ground deformation of the impact.
In this paper, Taiyuan city central one deep foundation pit monitoring data analysis, according to the simulation based on Biot's consolidation theory as the basis for the numerical simulation using cysoil Flac3D model, in-depth study of the waterproof curtain embedded into second patterns, head boundary conditions were used and two different lateral upper head supply position when the precipitation recharge seepage condition of four combinations and between the lining structure and ground deformation interaction; and change of groundwater level, soil properties, permeability coefficient, recirculation condition change induced effect of foundation pit surrounding ground settlement is studied.
In the end, the test method and the change law of the mechanical properties of soil mass before and after precipitation are analyzed and studied.
The main understanding and conclusions obtained through the above analysis are as follows:
1, the material constitutive model of cysoil is derived by using the Mohr Coulomb model, incremental elastic law rule, failure criterion and flow rule. Using this model, the precipitation recharge seepage variation and soil mechanics organically, combined with Biot's consolidation theory can well excavation and stress change between the role of reflect the seepage characteristics of groundwater. The simulation results are compared with the one central monitoring data, simulation of ground settlement agreement rate is more than 90%, the wall of underground continuous wall displacement of the anastomosis was 60%-80%, the level of support the supporting force of agreement rate reaches above 80%, indicating precipitation engineering excavation the model suitable for this paper.
2, through the simulation of the changes in various hydrologic parameters, the results are as follows:
1) the lateral fixed water head location of the head boundary condition is suitable for the first class and the second type of fixation mode. The upper fixed water supply location is suitable for the third type of fixation mode.
2) step by step precipitation and recharge irrigation and excavation operation is the best way to control the ground deformation around foundation pit. Recharge is the effective way to control land subsidence. The location of recharge well is the best in the depth of excavation (0.5 ~ 1) H.
3) according to the orthogonal principle provides a recharge well depth, pressure recharge, recharge well and the number of rows, the combination of different factors and factors of curtain depth on the ground subsidence contribution coefficient table to evaluate the impact of various parameters and the parameters of ground subsidence, so that the design and construction of the optimal economic return irrigation combination.
4) for concave curves of ground settlement caused by foundation pit precipitation from the foundation pit to the largest settlement point for a logarithmic curve from the outer boundary of the maximum settlement point to the precipitation affected area is linear regression. Given second kinds of embedded mode outside the foundation pit ground deformation and calculation formula of variation of permeability coefficient the relationship between.
5) considering the seepage recharge stress than that without considering the seepage effect, surface subsidence is reduced by 50%, 35% increase in heave, increase the horizontal displacement of the supporting structure 30%, increase in 15%. design should consider the seepage recharge support axial force level, to reduce the risk of supporting structure.
6) limit the horizontal displacement of the diaphragm wall under horizontal lateral support, the same section two small middle drum belly deflection shape. The maximum horizontal displacement of the wall under the top position at 0.85H in the wall, in the depth of excavation (0.4-0.85) H horizontal displacement increment, the paragraph is the weakest part of the supporting structure, is the key site set up support and construction monitoring.
7) decreases with increasing the elastic modulus of soil surface settlement; maximum surface settlement and elastic modulus curve is roughly polygonal shaped distribution. With the increase of soil modulus, deformation of slip surface in slope soil increases, slip surface becomes more and more steep, the extent of deformation of soil decreased. But soil modulus to improve the supporting effect of deformation supporting structure is small.
3, the experimental study of hydrologic parameters is obtained.
1) considering the disturbance degree of soil sample, the depth of soil sample, the release of soil samples, the degree of pore water pressure dissipation and the weight of infiltration coefficient on the soil layer, a correction formula for permeability coefficient measured in laboratory tests is put forward.
2) the precipitation process is equivalent to a preloading reinforcement. After precipitation, the compressive modulus of soil ES1-2 increases by 25%, cohesion increases by 33%, and the internal friction angle increases by 8%..
3) there is "hysteresis loop" in the soil of high pressure consolidation and multistage unloading test, and the slope of unloading curve is not consistent, but the path of rebound is almost a parallel line.
The results of this study is to draw on Taiyuan City Central No. 1 engineering support system, has certain reference and guidance for the design and construction of high water level of river terraces in the excavation of deep foundation pit, seepage field and supporting structure, has a certain significance to study the interaction theory of the surrounding environment the.

【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2013
【分類號(hào)】：TU470;TU46

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