1、重塑黃土論文：滲流條件下重塑黃土強度的變化規律試驗研究【中文摘要】滲流是黃土工程性質劣化的一個重要原因。當黃土作為防滲材料時,在長期滲流作用下,由于復雜的土-水相互作用將改變原來土體的物理力學性質,最終導致強度降低。因此,研究滲流條件下黃土的強度和化學成分等物理力學性質隨著時間的增長緩慢變化的規律具有重要的工程意義。鑒于室內模擬的難度,目前的研究主要集中于土-水相互作用機理上,對于滲流條件下黃土長期強度的研究極少。本文結合國家自然科學基金項目“黃土工程性質劣化機理與構筑物壽命預測研究”,以楊凌地區Q3重塑黃土為研究對象,通過室內試驗模擬自然狀態下土壩等黃土構筑物所經歷的長期滲流作用,研究了不同

2、pH值滲流溶液對土體短期強度的影響以及酸性溶液較長時間滲流作用下土體中碳酸鈣含量與抗剪強度之間的關系。土-水相互作用中主要有三種具有力學效應的化學作用即:溶蝕作用、沉淀或結晶作用和陽離子交換吸附作用。這三種作用發生的條件以及程度都受到土顆粒間水環境的影響。所以在不同pH值滲流溶液環境下,土體的短期強度也必然發生不同的變化。試驗研究發現:經過酸溶液滲流后土體的強度比用純水滲流之后的強度高,甚至會超過土樣的初始抗剪強度。酸性溶液滲流條件下,土中礦物成分在酸性環境中發生一系列化學反應,主要是HCO 3-易溶鹽在酸性環境下反應生成CO2氣體,對土體強度在一定程度上起到了正面作用;滲流作用下,以碳酸鈣為

3、主的膠結物以及其他鹽分發生溶蝕和沉淀或結晶作用,改變了土顆粒的聯結方式,陽離子交換吸附作用則改變土顆粒表面的雙電層。這一系列復雜的反應使土樣粘聚力c發生了不同程度的增大,而使內摩擦角發生了減小;在短期（10h）內,土體中碳酸鈣含量和強度之間沒有較強的相關性。這說明滲流初期土體中的物理化學作用比較劇烈,土中碳酸鈣的溶蝕作用不能主導土體的抗剪強度變化。而經過較長時間的滲流之后,土體中難溶鹽碳酸鈣的溶蝕將對土體強度的變化起決定作用。在酸性溶液較長時間的滲流作用下,土-水相互作用持續發生。試驗結果表明:此種情況下,由于碳酸鈣的溶蝕流失,土體強度的時程曲線將會呈現出波浪起伏的形態。在分析其影響機理的基礎

4、上,可以推斷在一定時間內土體強度時程曲線的波動幅度將逐漸減小,峰值強度也持續降低。對比發現:低壓實度土體對外部附加荷載（400kPa圍壓內）的反映相對遲鈍,具體表現為土體強度時程曲線在各圍壓情況下呈現良好的一致性;而高壓實度土體對外部附加荷載比較敏感,表現在不同圍壓情況下強度時程曲線都有差別,尤其是在低圍壓（200kPa）時。本文根據試驗結果模擬土體中碳酸鈣含量與強度（主應力差）相對變化率之間的關系,并建立了簡單的數學模型,這也是本次研究的一個創新點。但是其準確性以及模型參數的物理意義、獲取方法等還需要進行后續試驗研究?！居⑽恼縎eepage is an important reason

5、for the engineering properties deterioration of loess. The loessial physical and mechanical properties change with complex soil-water interactions carrying on under sustained seepage, which decreases its strength, when it is used as impermeable material. Therefore, it has important engineering signi

6、ficance to study on the law of loessial physical and mechanical properties （strength, chemical constituents, and so on） changing slowly with time-lapse. In view of the difficulty of laboratory simulation, the current researchs are concentrated on the mechanism of soil-water interactions, and little

7、on the loessial long-term strength under seepage. This paper studies on its short-term strength under seepage of different pH solutions and the relationship between its CaCO3 content and strength under sustained seepage of acidic solution by laboratory simulation, using Q3 remolded loess in Yangling

8、 as research object. It relies on the National Natural Science Foundation project“The Research of Properties Deterioration Mechanism of Loess Engineering and Life Prediction of Loess Structures”.It includes three chemical interactions with mechanical effect in soil-water interactions: dissolution, p

9、recipitation or crystallization, cation exchange adsorption. The water environment between soil particles affect on their occurrence and development. So the short-time strength of loess is different under seepage of different pH solutions. It is found through test that: The strength of loess after s

10、eepage of acidic solution is bigger than after seepage of pure water, even more than its initial strength. A series of chemical reaction take place between the bicarbonate in soil and acid under seepage of acidic solution, which produced carbon dioxide gas to increase the strength of loess; The diss

11、olution and precipitation or crystallization of calcareous cement and other soil salinity changed the connection between soil particles, and the cation exchange adsorption changed electric double layer on particle surface. This improved the cohesion while decreased the internal friction angle. It sh

12、ows a weak correlation between its CaCO3 content and strength in 10h. This suggests that the dissolution of CaCO3 is not the dominant factor of loess strength in the early seepage, but it could determine loess strength after long-time seepage. Soil-water interactions are continuous under long-time s

13、eepage of acidic solution. The results show that: The time-history curves present wave shape. Based on mechanism analysis, it can be deduced that the peak strength and fluctuation range of the time-history curves will decreased gradually. Comparison study shows that the remolded loess with lower com

14、pactness responded badly to external additional load （confining pressures lower than 400kPa）, while the time-history curves present strong consistency; But the remolded loess with higher compactness make good respond to external additional load, while the time-history curves are different under diff

15、erent confining pressures, especially lower confining pressures （200kPa）.This paper simulated the correlation between CaCO3 content and the relative change rate of loess strength and builds a simple mathematical model, based on the test results. It is an innovative point of this research. But it nee

16、ds more work to verify its accuracy, to determine the physical significance and acquisition method of the model.【關鍵詞】重塑黃土 長期滲流 強度 碳酸鈣含量【英文關鍵詞】remolded loess sustained seepage strength CaCO3 content【目錄】滲流條件下重塑黃土強度的變化規律試驗研究摘要5-7ABSTRACT7-8第一章 緒論11-261.1 引言111.2 飽和粘性土的滲透特性11-181.2.1 粘性土孔隙水的分類11-121.2.2

17、 粘性土中孔隙水的滲流特性121.2.3 飽和粘性土的滲透特性12-151.2.4 飽和粘性土滲透特性研究現狀15-161.2.5 長期滲流的研究現狀16-181.3 水-土化學作用機理研究18-241.3.1 水-土化學作用機理19-201.3.2 水-土化學作用研究進展20-221.3.3 酸堿環境下水-土化學作用研究22-241.4 研究目的及內容24-261.4.1 研究目的241.4.2 研究內容24-26第二章 試驗原理及方法26-322.1 試驗原理26-272.2 試驗方法27-322.2.1 滲流水溶液配制27-282.2.2 試驗材料及試樣制備28-302.2.3 試驗內容30-32第三章 不同 pH 值溶液滲流對重塑黃土強度的影響研究32-423.1 引言323.2 重塑黃土抗剪強度及其指標的獲取方法32-343.3 不同pH 值溶液滲流對重塑黃土抗剪強度的影響34-373.3.1 不同pH 值溶液滲流對土樣主應力差的影響34-363.3.2 不同pH 值溶液滲流對土樣c、值的影響36-373.4 滲流對重塑黃土強度及c、值的影響37-383.5 碳酸鈣含量對重塑黃土