廈門地區(qū)非飽和殘積土土水特征及強(qiáng)度性狀研究
發(fā)布時(shí)間：2018-10-20 07:00
【摘要】：殘積土層約占廈門島土地面積的三分之二,是工程建設(shè)巖土層的重要組成部分。在自然或人為地改變環(huán)境條件下,殘積土常經(jīng)受脫濕、增濕及干濕交替作用。此時(shí),殘積土?xí)尸F(xiàn)出與其在飽和狀態(tài)迥異的體積、強(qiáng)度、滲透和固結(jié)等性狀。非飽和土的強(qiáng)度在土坡穩(wěn)定、地基承載力及側(cè)向土壓力等分析計(jì)算中起著重要作用。而土水特征曲線(簡(jiǎn)稱SWCC)是基質(zhì)吸力與含水量或飽和度的關(guān)系曲線,它可幫助我們了解含水量對(duì)非飽和土強(qiáng)度的影響。因此,研究非飽和殘積土的土水特征曲線及抗剪強(qiáng)度具有重要的工程意義和應(yīng)用前景。本文針對(duì)廈門地區(qū)常見(jiàn)的殘積砂質(zhì)粘性土和殘積粘土,進(jìn)行了不同干密度、含水量、豎向應(yīng)力和干濕循環(huán)作用下SWCC測(cè)定、無(wú)側(cè)限抗壓強(qiáng)度和直接剪切的試驗(yàn)研究,建立了SWCC模型、無(wú)側(cè)限抗壓強(qiáng)度及剪切強(qiáng)度模型。主要研究?jī)?nèi)容如下： 1.采用濾紙法測(cè)定基質(zhì)吸力,分析了干密度、含水量、豎向應(yīng)力及干濕循環(huán)作用等因素對(duì)殘積砂質(zhì)粘性土和殘積粘土的脫濕曲線、吸濕曲線及滯回環(huán)的影響。試驗(yàn)結(jié)果表明,砂質(zhì)粘性土的SWCC與粘土的SWCC相比,前者的脫濕速率較大,進(jìn)氣值較低,持水能力較弱。砂質(zhì)粘性土的SWCC對(duì)干密度和豎向應(yīng)力的變化較敏感,而粘土SWCC對(duì)含水量的變化較敏感；3次干濕循環(huán)中,第1次干濕循環(huán)對(duì)兩類殘積土SWCC的影響較大。 2.選擇了6個(gè)SWCC模型,剔除殘余飽和度參數(shù),建立修正SWCC模型。設(shè)置了考慮參數(shù)個(gè)數(shù)的模型權(quán)值,根據(jù)已測(cè)殘積土的SWCC試驗(yàn)數(shù)據(jù),綜合考慮擬合精度及模型參數(shù)個(gè)數(shù),評(píng)估各修正SWCC模型的優(yōu)劣。計(jì)算結(jié)果表明修正Gardner模型是最適合于廈門地區(qū)的殘積砂質(zhì)粘性土和粘土的SWCC模型。推導(dǎo)了修正的SWCC模型特征值計(jì)算公式,它們可取代作圖法,從而較準(zhǔn)確地計(jì)算出空氣進(jìn)氣值、曲線拐點(diǎn)的斜率、殘余基質(zhì)吸力及殘余飽和度等參數(shù)。 3.設(shè)計(jì)了殘積砂質(zhì)粘性土和粘土的無(wú)側(cè)限抗壓強(qiáng)度試驗(yàn),得到了考慮初始干密度和含水量下砂質(zhì)粘性土的無(wú)側(cè)限抗壓強(qiáng)度經(jīng)驗(yàn)?zāi)Ｐ秃筒煌跏己肯抡惩恋臒o(wú)側(cè)限抗壓強(qiáng)度經(jīng)驗(yàn)?zāi)Ｐ�。另�?測(cè)定了不同干濕幅度、路徑及次數(shù)下兩類殘積土的無(wú)側(cè)限抗壓強(qiáng)度,得到了干濕幅度、次數(shù)和路徑對(duì)兩類殘積土的無(wú)側(cè)限抗壓強(qiáng)度的影響規(guī)律。 4.采用普通的直剪儀進(jìn)行非飽和殘積土的剪切強(qiáng)度試驗(yàn),并用濾紙法測(cè)定各不同含水量狀態(tài)下的基質(zhì)吸力,研究剪切強(qiáng)度及強(qiáng)度指標(biāo)隨初始含水量的變化規(guī)律,建立不同初始含水量下殘積砂質(zhì)粘性土和粘土的剪切強(qiáng)度模型,能夠較好地預(yù)測(cè)殘積土的抗剪強(qiáng)度及強(qiáng)度指標(biāo)。同時(shí),開(kāi)展了干濕循環(huán)作用對(duì)殘積土的試驗(yàn)研究,得到了不同干濕循環(huán)幅度、路徑及次數(shù)下兩類殘積土的剪切強(qiáng)度和強(qiáng)度指標(biāo)的變化規(guī)律,為今后干濕循環(huán)作用下殘積土強(qiáng)度模型的研究奠定基礎(chǔ)。
[Abstract]:The residual soil layer accounts for 2/3 of the land area of Xiamen Island and is an important part of the engineering construction of geotechnical strata. Under natural or artificial environmental conditions, residual soils are often subjected to dehumidification, humidification, and alternate drying and wetting. At this time, the residual soil will show different volume, strength, permeability and consolidation from its saturation state. The strength of unsaturated soil plays an important role in the analysis and calculation of slope stability, foundation bearing capacity and lateral earth pressure. The soil-water characteristic curve (SWCC) is the relationship between the matrix suction and water content or saturation, which can help us understand the influence of water content on the strength of unsaturated soil. Therefore, the study of soil water characteristic curve and shear strength of unsaturated residual soil has important engineering significance and application prospect. In this paper, SWCC measurement, unconfined compressive strength and direct shear of residual sandy clay and residual clay, under different dry density, water content, vertical stress and dry-wet cycle, are studied in Xiamen area. SWCC model, unconfined compressive strength and shear strength model are established. The main contents are as follows: 1. The effects of dry density, moisture content, vertical stress and dry wet cycle on the dehumidification curve, hygroscopic curve and hysteresis loop of residual sandy clay and residual clay were analyzed by filter paper method. The experimental results show that the SWCC of sandy clay is higher than that of clay SWCC, the former has higher moisture removal rate, lower inlet air value and weaker water holding capacity. The SWCC of sandy clay is more sensitive to the change of dry density and vertical stress, while the clay SWCC is more sensitive to the change of water content, and the first dry and wet cycle has a great effect on the SWCC of the two types of residual soils in three dry and wet cycles. 2. Six SWCC models were selected and the residual saturation parameters were eliminated. The modified SWCC model was established. The weight value of the model considering the number of parameters is set. According to the SWCC test data of the measured residual soil, the fitting accuracy and the number of model parameters are considered synthetically to evaluate the merits and demerits of each modified SWCC model. The results show that the modified Gardner model is the most suitable SWCC model for residual sandy clay and clay in Xiamen area. The modified formulas for calculating the eigenvalues of SWCC model are derived, which can replace the drawing method, so that the parameters such as air intake value, slope of curve inflection point, residual matrix suction and residual saturation can be calculated more accurately. The unconfined compressive strength tests of residual sandy clay and clay are designed. The empirical model of unconfined compressive strength of sandy clay under initial dry density and water content and the empirical model of unconfined compressive strength of clay with different initial water content are obtained. In addition, the unconfined compressive strength of the two types of residual soils under different dry-wet ranges, paths and times were measured, and the influence of dry and wet amplitude, times and paths on the unconfined compressive strength of the two types of residual soils was obtained. 4. The shear strength of unsaturated residual soil was tested with a direct shear apparatus, and the matrix suction under different water content was measured by filter paper method. The variation of shear strength and strength index with initial water content was studied. The shear strength model of residual sandy clay and clay under different initial water content can be used to predict the shear strength and strength index of residual sandy clay. At the same time, the experimental study of dry and wet cycling on residual soil was carried out, and the change rules of shear strength and strength index of two kinds of residual soil under different dry-wet cycle amplitude, path and times were obtained. It will lay a foundation for the study of strength model of residual soil under dry and wet cycle in the future.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU41;TU44
本文編號(hào)：2282403
[Abstract]:The residual soil layer accounts for 2/3 of the land area of Xiamen Island and is an important part of the engineering construction of geotechnical strata. Under natural or artificial environmental conditions, residual soils are often subjected to dehumidification, humidification, and alternate drying and wetting. At this time, the residual soil will show different volume, strength, permeability and consolidation from its saturation state. The strength of unsaturated soil plays an important role in the analysis and calculation of slope stability, foundation bearing capacity and lateral earth pressure. The soil-water characteristic curve (SWCC) is the relationship between the matrix suction and water content or saturation, which can help us understand the influence of water content on the strength of unsaturated soil. Therefore, the study of soil water characteristic curve and shear strength of unsaturated residual soil has important engineering significance and application prospect. In this paper, SWCC measurement, unconfined compressive strength and direct shear of residual sandy clay and residual clay, under different dry density, water content, vertical stress and dry-wet cycle, are studied in Xiamen area. SWCC model, unconfined compressive strength and shear strength model are established. The main contents are as follows: 1. The effects of dry density, moisture content, vertical stress and dry wet cycle on the dehumidification curve, hygroscopic curve and hysteresis loop of residual sandy clay and residual clay were analyzed by filter paper method. The experimental results show that the SWCC of sandy clay is higher than that of clay SWCC, the former has higher moisture removal rate, lower inlet air value and weaker water holding capacity. The SWCC of sandy clay is more sensitive to the change of dry density and vertical stress, while the clay SWCC is more sensitive to the change of water content, and the first dry and wet cycle has a great effect on the SWCC of the two types of residual soils in three dry and wet cycles. 2. Six SWCC models were selected and the residual saturation parameters were eliminated. The modified SWCC model was established. The weight value of the model considering the number of parameters is set. According to the SWCC test data of the measured residual soil, the fitting accuracy and the number of model parameters are considered synthetically to evaluate the merits and demerits of each modified SWCC model. The results show that the modified Gardner model is the most suitable SWCC model for residual sandy clay and clay in Xiamen area. The modified formulas for calculating the eigenvalues of SWCC model are derived, which can replace the drawing method, so that the parameters such as air intake value, slope of curve inflection point, residual matrix suction and residual saturation can be calculated more accurately. The unconfined compressive strength tests of residual sandy clay and clay are designed. The empirical model of unconfined compressive strength of sandy clay under initial dry density and water content and the empirical model of unconfined compressive strength of clay with different initial water content are obtained. In addition, the unconfined compressive strength of the two types of residual soils under different dry-wet ranges, paths and times were measured, and the influence of dry and wet amplitude, times and paths on the unconfined compressive strength of the two types of residual soils was obtained. 4. The shear strength of unsaturated residual soil was tested with a direct shear apparatus, and the matrix suction under different water content was measured by filter paper method. The variation of shear strength and strength index with initial water content was studied. The shear strength model of residual sandy clay and clay under different initial water content can be used to predict the shear strength and strength index of residual sandy clay. At the same time, the experimental study of dry and wet cycling on residual soil was carried out, and the change rules of shear strength and strength index of two kinds of residual soil under different dry-wet cycle amplitude, path and times were obtained. It will lay a foundation for the study of strength model of residual soil under dry and wet cycle in the future.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU41;TU44
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