本文選題：砂土液化　切入點(diǎn)：振動臺試驗(yàn)　出處：《太原理工大學(xué)》2017年碩士論文

【摘要】：液化土加固問題一直是巖土工程重點(diǎn)關(guān)注及研究的課題。碎石樁和水泥土樁被廣泛應(yīng)用于液化土地基處理。碎石樁的排水、擠密效果以及水泥土樁對地基豎向承載力的提高效果均在實(shí)際工程中得到了普遍的認(rèn)可。但其對液化土加固的機(jī)理研究仍有不足,需要進(jìn)一步深入研究及科學(xué)試驗(yàn)的認(rèn)證。本文依托國家自然基金“樁體加固液化砂土作用機(jī)理的試驗(yàn)研究”(項(xiàng)目號50578104)、山西省交通廳科技項(xiàng)目“黃土地區(qū)樁體加固砂土抗液化機(jī)理的研究”(合同編號10-1-06)以及山西省交科院黃土實(shí)驗(yàn)室開放基金項(xiàng)目“液化土層樁基礎(chǔ)承載性狀的試驗(yàn)研究”(KLTLR-Y13-3),展開以液化土地基加固機(jī)理為背景、以1:18的相似幾何比模擬地表以下8.64m范圍內(nèi)的砂土液化土層震害情況的研究,通過三組液化模型即碎石樁加固液化土模型、水泥土樁加固液化土模型以及碎石樁與水泥土樁復(fù)合加固液化土模型分別進(jìn)行振動臺試驗(yàn),記錄不同加固模型不同埋深、不同水平位置處的孔隙水壓力、土壓力及位移時程曲線并進(jìn)行整理分析得出如下結(jié)論:宏觀現(xiàn)象反映:不論哪種加固模型,在循環(huán)荷載振動作用下,樁頂均出現(xiàn)排水,且隨著碎石樁根數(shù)的增加,排水量逐漸增多,振動結(jié)束后,整體表面呈凹狀并向振動方向傾斜,且局部出現(xiàn)沙丘,碎石樁加固模型下部土體密實(shí),水泥土樁加固模型土體上部密實(shí),碎石樁和水泥土樁復(fù)合加固模型土整體呈現(xiàn)較密實(shí)。由孔隙水壓力分析得出:(1)不論哪種加固模型,孔隙水壓力時程曲線均隨振動荷載施加孔隙水壓力值增大,達(dá)到峰值保持幾秒后,隨振動開始緩慢下降,直到試驗(yàn)結(jié)束。(2)同一種加固模型,孔隙水壓力均隨埋深的加深不斷增大;(3)同一位置處,水泥土樁加固模型的孔隙水壓力最大,復(fù)合樁加固模型次之,碎石樁加固模型最小,說明碎石樁提供了良好的排水通道,有助于孔隙水壓力的消散。由土壓力分析得出:(1)不論哪種加固模型,土壓力時程曲線均隨振動荷載施加土壓力在靜壓力附近上下波動幾秒后,土壓力迅速下降到最小值,隨后以此定值波動直到試驗(yàn)結(jié)束;同一水平面上,0cm處的土壓力減小量最小,-14cm處次之,14cm處最大。(2)同一加固模型土壓力均隨著埋深的加深不斷增大;(3)相同位置處,碎石樁加固模型的土壓力最大,水泥土樁加固模型次之,復(fù)合樁加固模型最小,比較相同條件下,復(fù)合樁加固模型中樁體分擔(dān)的土壓力最大。(4)土壓力與埋深、水平位置三者關(guān)系滿足p=z_0+ax+by+cx~2+dy~2+fxy(y—埋深/cm;x—水平位置/cm;p—土壓力/kpa;z0,a,b,c,d,f—與加固模型有關(guān)的系數(shù))關(guān)系式,由此可推算出三種加固模型不同位置的土壓力。由沉降量分析得出:(1)不論哪種加固模型,振動開始幾秒沉降量均不變,隨振動繼續(xù),沉降量迅速到最大,之后以此值保持到試驗(yàn)結(jié)束;同一埋深平面沉降呈凹型并傾斜,且隨著埋深的加深,凹沉的曲率減小;(2)相同水平位置處,隨著埋深的增加,沉降量在不斷的減小,且隨著碎石樁根數(shù)的增加,沉降量逐漸減小;(3)沉降量與埋深和水平位置的關(guān)系為:s=z_0+ax+by+cx~2+dy~2+fxy(y—埋深,單位cm;x—水平位置,單位cm;S—沉降量,單位mm;Z_0,a,b,c,d,f—與加固模型有關(guān)的系數(shù))關(guān)系式�？梢杂么耸酵扑愠鋈N加固模型任一位置的沉降量�？傊�,無論哪種樁體加固模型,樁體中部容易發(fā)生膨脹和斷裂;且相同條件下,復(fù)合樁加固模型中樁體分擔(dān)的土壓力最大;水泥土樁加固的沉降量大于復(fù)合樁加固,碎石樁加固的最小,說明碎石樁加固有利于抑制土體沉降。因此,從綜合因素考慮,建議實(shí)際工程盡量考慮采用碎石樁與水泥土樁復(fù)合加固形式加固液化土。
[Abstract]:The problem of soil liquefaction reinforcement has been the focus of attention and research of geotechnical engineering subject. Gravel pile and cement soil pile is widely used in the treatment of liquefied soil foundation. The drainage gravel pile, and the compaction effect of soil cement pile foundation vertical bearing capacity and improve the effect in practical engineering has been widely accepted. But the study on the mechanism of liquefaction of soil reinforcement is still inadequate, need further research and scientific test certification. Experimental study of the National Natural Science Foundation "pile reinforcement mechanism of sand soil liquefaction based on" (Project No. 50578104), on the loess area of pile reinforcement sand soil anti liquefaction mechanism of Shanxi provincial Department of Communications Science and technology project "(" the contract number 10-1-06) experimental study on bearing behavior of pile foundation and soil liquefaction in Shanxi province Jiaoke hospital laboratory loess open fund project "(KLTLR-Y13-3), launched in the liquefied soil foundation reinforcement The mechanism for the background, in a similar study than in the sand soil liquefaction damage simulation of 8.64m under the surface within the scope of the geometry of the 1:18, through three sets of liquefied model gravel pile liquefied soil model, the soil cement pile reinforcement and soil liquefaction model of gravel pile and cement soil pile composite reinforcement soil liquefaction model are respectively used in shaking table test, record different reinforcement model of different depth, pore water pressure in different horizontal positions, soil pressure and displacement curve and analysis draws the following conclusion: macroscopic phenomena reflect: no matter what kind of reinforcement model, cyclic loading in vibration under the pile top are drainage, and with the increase of gravel pile root number, drainage the amount gradually increased, after the vibration, the whole surface is concave and is inclined to the direction of vibration, and the emergence of local sand dunes, the gravel pile model of lower soil compaction, soil cement pile and soil on the solid model Department of dense, gravel pile and cement soil pile composite reinforcement model of soil showed relatively compact. The pore water pressure is obtained by analysis: (1) no matter what kind of reinforcement model, pore water pressure curve with the vibration load imposed by the pore water pressure increases and the peak hold after a few seconds, with vibration began to decrease slowly. Until the end of the experiment. (2) with a reinforcement model, pore water pressure increases with the depth of further increasing; (3) at the same position, the pore water pressure of soil cement pile reinforcement model, composite pile reinforcement model of gravel pile reinforcement model that provides the minimum drainage gravel pile a good channel, contribute to the dissipation of pore water pressure. The earth pressure obtained by analysis: (1) no matter what kind of reinforcement model, soil pressure curve with the vibration load of earth pressure in the static pressure near the fluctuation after a few seconds, the earth pressure decreases to the minimum value, with the 鍚庝互姝ゅ畾鍊兼嘗鍔ㄧ洿鍒拌瘯楠岀粨鏉，

本文編號：1725919