發(fā)布時(shí)間：2019-02-09 16:02

【摘要】：機(jī)械壓實(shí)和化學(xué)灌漿是現(xiàn)今土體加固處理應(yīng)用最為廣泛的兩種方式,但其高成本、高能耗以及對(duì)環(huán)境污染和破壞的缺點(diǎn)促使了對(duì)新型土體加固技術(shù)的探索。新世紀(jì)以來(lái),基于理、化、生交叉學(xué)科衍生出的一種微生物誘導(dǎo)碳酸鈣沉淀(MICP)技術(shù)得到了廣泛重視與研究,研究表明,該項(xiàng)技術(shù)可以顯著改善土體強(qiáng)度、剛度、滲透性及抗液化性能,并且相比于傳統(tǒng)土體改良工藝,其綠色環(huán)保、環(huán)境友好型特點(diǎn)更加符合可持續(xù)發(fā)展理念。本文主要開展了巴氏芽孢桿菌(Sporosarcina pasteurii)誘導(dǎo)碳酸鈣沉淀影響因素及灌漿膠結(jié)砂土強(qiáng)度試驗(yàn)研究,并對(duì)微生物固化砂柱內(nèi)部微觀結(jié)構(gòu)進(jìn)行了觀測(cè)研究以探明膠結(jié)機(jī)理,主要研究?jī)?nèi)容和結(jié)論如下:(1)首先對(duì)巴氏芽孢桿菌誘導(dǎo)碳酸鈣沉積影響因素進(jìn)行了研究,采用對(duì)比試驗(yàn)對(duì)鈣源的選擇進(jìn)行了優(yōu)化;膠結(jié)液濃度小于1.0mol/L時(shí),隨著濃度的提升碳酸鈣產(chǎn)量得以增加,但膠結(jié)液濃度過高鈣離子對(duì)脲酶活性產(chǎn)生較大的抑制,碳酸鈣產(chǎn)量減少;p H值在6~9之間對(duì)誘導(dǎo)碳酸鈣的影響較小,但碳酸鈣產(chǎn)量隨著溫度的上升而增加。(2)開展了巴氏芽孢桿菌菌液灌注加固砂土試驗(yàn)研究,采用混合注入法和分步灌漿法膠結(jié)砂柱發(fā)現(xiàn),分步灌注更有利于砂土的整體固化效果;對(duì)比分析單一濃度和高、低濃度膠結(jié)液結(jié)合灌注對(duì)砂柱膠結(jié)效果的影響,基于微生物固化砂柱進(jìn)行無(wú)側(cè)限抗壓試驗(yàn),并分析了不同灌注方式對(duì)砂柱的破壞模式、碳酸鈣含量和強(qiáng)度的影響,高、低濃度結(jié)合灌注能在較少的灌注次數(shù)下獲得比較高的強(qiáng)度,最高強(qiáng)度達(dá)到10MPa左右,不同灌注方式對(duì)砂柱的破壞模式和碳酸鈣含量上沒有太大的影響,不同試樣的強(qiáng)度區(qū)別主要是微生物誘導(dǎo)的碳酸鈣在砂柱中分布均勻性不同導(dǎo)致。(3)利用掃描電子顯微鏡(SEM)對(duì)微生物固化砂柱進(jìn)行微觀測(cè)試,探明砂顆粒間的膠結(jié)方式,并通過化學(xué)法誘導(dǎo)碳酸鈣加固砂土開展對(duì)比試驗(yàn)。試驗(yàn)發(fā)現(xiàn)微生物誘導(dǎo)球形狀和球形聚集體碳酸鈣晶體將砂顆粒包裹,并且尺寸較小晶體間相互交錯(cuò)嵌合將砂顆粒膠結(jié)成整體,砂顆粒間依舊保存著一定孔隙,而化學(xué)法沉積碳酸鈣晶體呈斜六面體尺寸較大并未將砂顆粒粘結(jié)成整體。
[Abstract]:Mechanical compaction and chemical grouting are the two most widely used methods of soil reinforcement, but their high cost, high energy consumption and the shortcomings of environmental pollution and damage promote the exploration of new soil reinforcement technology. Since the new century, a microorganism induced calcium carbonate precipitation (MICP) technique derived from the interdisciplinary disciplines of science, chemistry and biology has been widely studied. The results show that this technique can significantly improve the strength and stiffness of soil. The properties of permeability and liquefaction resistance are more consistent with the concept of sustainable development than the traditional soil improvement technology. In this paper, the influencing factors of calcium carbonate precipitation induced by Bacillus pasteurium (Sporosarcina pasteurii) and the strength test of grouting cemented sand soil were studied, and the microstructure of microorganism solidified sand column was observed to find out the cementation mechanism. The main contents and conclusions are as follows: (1) the factors affecting the calcium carbonate deposition induced by Bacillus pasteurium were studied, and the selection of calcium source was optimized by contrast test. When the concentration of cementing solution was less than 1.0mol/L, the yield of calcium carbonate increased with the increase of concentration, but too high concentration of calcium in cementing solution inhibited urease activity greatly, and the yield of calcium carbonate decreased. The pH value between 6 and 9 had little effect on the induced calcium carbonate, but the yield of calcium carbonate increased with the increase of temperature. (2) A study on the reinforcement of sand soil with Bacillus pasteuris liquid was carried out. By using mixed injection method and step grouting method to cement sand column, it is found that step by step grouting is more favorable to the overall solidification effect of sand. The effect of single concentration, high concentration and low concentration of cementing liquid on the cementation effect of sand column was compared and analyzed. Based on the microorganism solidified sand column, the unconfined compression test was carried out, and the failure modes of different pouring methods to sand column were analyzed. Under the influence of calcium carbonate content and strength, high and low concentration of calcium carbonate can get higher intensity under less perfusion times, and the maximum strength is about 10MPa. Different pouring methods have no great effect on the failure mode and calcium carbonate content of sand column. The difference in strength of different samples is mainly due to the difference in the distribution uniformity of calcium carbonate induced by microorganism in the sand column. (3) the microcosmic test of microorganism solidified sand column is carried out by scanning electron microscope (SEM), and the cementation mode between sand particles is proved. A comparative experiment was carried out to induce calcium carbonate to reinforce sandy soil by chemical method. It was found that the microorganism induced the ball shape and the spherical aggregate calcium carbonate crystal to wrap the sand particles, and the smaller crystals interlaced each other to form the whole sand particles, and there were still some pores in the sand particles. However, the larger size of the hexahedron crystal deposited by the chemical method did not bind the sand particles into a whole.
【學(xué)位授予單位】：江蘇科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU472

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