【摘要】：以汕頭沿海經(jīng)濟(jì)帶的大范圍吹填場(chǎng)地的高等級(jí)公路地基處理工程為依托，通過(guò)現(xiàn)場(chǎng)試驗(yàn)研究典型路段采用堆載降水預(yù)壓強(qiáng)夯聯(lián)合法加固軟土地基的加固機(jī)理，分析地基變形、孔隙水壓力隨時(shí)間的變化規(guī)律、強(qiáng)夯的動(dòng)力特性、強(qiáng)夯在軟土地基固結(jié)中的作用、處理后軟土路基的加固效果,此基礎(chǔ)上對(duì)試驗(yàn)路段建立軟土固結(jié)有限元數(shù)值分析模型，將計(jì)算結(jié)果與現(xiàn)場(chǎng)監(jiān)測(cè)數(shù)據(jù)作對(duì)比，得到如下結(jié)論： （1）現(xiàn)場(chǎng)采用二級(jí)堆載填土加降水及兩次強(qiáng)夯加固軟土地基。加固后②1層淤泥的粘聚力值由8.7kPa提高到18.6kPa，④1層淤泥質(zhì)土的粘聚力值由17.2kPa提高到29.85kPa；地基承載力特征值大于120kPa。 （2）現(xiàn)場(chǎng)試驗(yàn)歷時(shí)210d，固結(jié)總沉降527mm，其中第一級(jí)堆載填土1.3m，歷時(shí)95d，固結(jié)沉降279mm，，強(qiáng)夯結(jié)束后，固結(jié)沉降428mm；第二級(jí)堆載填土2m，歷時(shí)110d，固結(jié)沉降62mm，強(qiáng)夯結(jié)束后，固結(jié)沉降99mm；第一次強(qiáng)夯結(jié)束后沉降最大值為149mm，占總沉降量的28%。第二次強(qiáng)夯結(jié)束后引起的沉降最大值為82mm，占總沉降量的15.7%，強(qiáng)夯加固作用效果明顯。 （3）超孔隙水壓力在軟基處理過(guò)程中，變化最大值都是位于強(qiáng)夯期間，增高最大值達(dá)到10kPa左右，經(jīng)過(guò)2d后恢復(fù)到強(qiáng)夯前超孔隙水壓值，強(qiáng)夯施工的兩遍點(diǎn)夯最佳間隔時(shí)間大于2d。 （4）強(qiáng)夯作用下測(cè)點(diǎn)的加速度峰值隨著測(cè)點(diǎn)與夯點(diǎn)距離的增加而不斷衰減，同一測(cè)點(diǎn)豎直方向加速度值最大是水平方向的2.4倍,強(qiáng)夯的水平影響范圍在15~20m左右；從對(duì)同一夯點(diǎn)的多遍夯擊來(lái)看，第三遍夯擊測(cè)得的加速度值最大，前兩遍夯擊能大部分消耗在對(duì)表層土的壓密過(guò)程中。 （5）數(shù)值模擬結(jié)果表明，在填土階段數(shù)值模擬結(jié)果與現(xiàn)場(chǎng)實(shí)測(cè)監(jiān)測(cè)的沉降曲線(xiàn)比較一致。在兩次堆載過(guò)程中，第一級(jí)填土數(shù)值模擬的沉降值與現(xiàn)場(chǎng)監(jiān)測(cè)數(shù)據(jù)相比大2.8%；但第二級(jí)填土數(shù)值模擬的沉降值比現(xiàn)場(chǎng)監(jiān)測(cè)數(shù)據(jù)小13%。
[Abstract]:Based on the foundation treatment project of high grade highway in Shantou coastal economic belt, the consolidation mechanism of soft soil foundation strengthened by heaped precipitation preloading and dynamic compaction method is studied by field test, and the deformation of foundation is analyzed. The variation law of pore water pressure with time, the dynamic characteristics of dynamic compaction, the effect of dynamic compaction in consolidation of soft soil foundation, the reinforcement effect of soft soil subgrade after treatment, and the finite element numerical analysis model of consolidation of soft soil in test section are established. By comparing the calculation results with the field monitoring data, the following conclusions are obtained: (1) the second stage heaped fill and precipitation and twice dynamic compaction are used to reinforce the soft soil foundation in the field. The cohesion of 21 layers of silt is increased from 8.7kPa to 18.6 KPA and the cohesion of 41 layers of silt is increased from 17.2kPa to 29.85 KPA, and the characteristic value of foundation bearing capacity is more than 120 KPA. (2) the site test lasted 210 days, and the total consolidation settlement was 527mm, among which 1.3m, 95 days, 279mm, 428mm after dynamic compaction; The second stage of loading fill is 2 m, lasting 110 days, the consolidation settlement is 62 mm, the consolidation settlement is 99 mm after the completion of the dynamic compaction, and the maximum settlement is 149 mm after the first dynamic compaction, accounting for 28% of the total settlement. The maximum settlement caused by the second dynamic compaction is 82 mm, accounting for 15. 7 mm of the total settlement, and the effect of dynamic compaction is obvious. (3) during the treatment of soft foundation, the maximum change of excess pore water pressure is in the period of dynamic compaction, the maximum value of the increase reaches about 10kPa, and after 2 days, it recovers to the value of excess pore water pressure before dynamic compaction. The optimum interval time of double point ramming is more than 2 days. (4) the acceleration peak of the measured point decreases continuously with the increase of the distance between the measuring point and the tamping point. The maximum vertical acceleration of the same measuring point is 2.4 times that of the horizontal direction, and the horizontal influence range of the dynamic compaction is about 15 ~ 20m; According to the multiple tamping at the same tamping point, the acceleration measured by the third tamping is the largest, and most of the first two tamping energies are consumed in the compaction process of the surface soil. (5) the numerical simulation results show that the numerical simulation results are in good agreement with the measured settlement curves in the filling stage. In the course of two heaps, the settlement value of the first stage filling numerical simulation is 2.8 larger than that of the field monitoring data, but the settlement value of the second stage filling numerical simulation is 13% smaller than that of the field monitoring data.
【學(xué)位授予單位】：河北大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：U416.1

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