本文選題：花崗巖殘積土　切入點(diǎn)：崩崗　出處：《華中農(nóng)業(yè)大學(xué)》2015年碩士論文

【摘要】：花崗巖殘積土廣泛分布于中國(guó)南方,形成于花崗巖殘積土上的崩崗、滑坡是南方水土流失的重要類(lèi)型。花崗巖殘積土具有顯著的不均勻性及各向異性、軟化性、崩解性,是一種結(jié)構(gòu)特殊的土壤。采取湖北省通城縣發(fā)育典型、分層明顯(表土層、紅土層、砂土層、碎屑層)的花崗巖殘積土,進(jìn)行三軸固結(jié)不排水實(shí)驗(yàn)和直剪快剪實(shí)驗(yàn),結(jié)合不同土層花崗巖殘積土的基本性質(zhì),研究發(fā)現(xiàn):1、不同土層應(yīng)力應(yīng)變關(guān)系均呈應(yīng)變硬化型,表現(xiàn)為塑性破壞,對(duì)于同一種土,4種圍壓下,應(yīng)力-應(yīng)變曲線間距均比較明顯;紅土層和砂土層在應(yīng)變初期,偏應(yīng)力變化受?chē)鷫河绊戄^小,與應(yīng)變水平關(guān)系密切;在同等圍壓條件下,表土層破壞所需的偏應(yīng)力較小,而碎屑層所破壞的偏應(yīng)力較大。毛管孔隙度在一定程度上影響了土體的孔隙壓力,破壞比Rf變異系數(shù)與毛管持水量極其顯著相關(guān),毛管孔隙度的變化是影響土體破壞比Rf發(fā)生變異的原因,即孔隙的突變影響土體破壞比在一定程度上發(fā)生變化。2、花崗巖殘積土的軟化性非常顯著,4層土內(nèi)摩擦角均和黏聚力均出現(xiàn)先增大后減小的趨勢(shì),黏聚力峰值出現(xiàn)在的平均含水率8.11%,內(nèi)摩擦角峰值出現(xiàn)在的平均含水率11.76%,在含水率在10%左右時(shí),花崗巖殘積土可能獲得最大的抗剪強(qiáng)度值,當(dāng)超過(guò)一定含水率后,隨著花崗巖殘積土含水量的增加,其強(qiáng)度顯著降低。表現(xiàn)為黏聚力迅速消散,內(nèi)摩擦角銳減,內(nèi)摩擦角的大幅降低可能是強(qiáng)度降低的主因�；◢弾r殘積土的孔隙發(fā)育,過(guò)多的水分起到了分散土粒的作用,降低了顆粒間的接觸作用。3、在處于含水率(平均為23.98%)無(wú)顯著差異的條件下(p0.5),碎屑層土體的黏聚力為顯著低于其它三層,表土層、紅土層、砂土層之間的黏聚力差異不顯著。黏聚力在表土層和碎屑層的變異較小,在紅土層和砂土層的變異較大。4層土的內(nèi)摩擦角變異均較小,表土層的內(nèi)摩擦角最小,數(shù)值分布較為集中,與相鄰的紅土層之間并無(wú)顯著性差異。紅土層的內(nèi)摩擦角處于中間水平,表現(xiàn)為只與碎屑層有顯著性差異,這可能是由于砂土層的顆粒分布、密度、膠結(jié)作用物、空隙條件等均處于適中水平的原因。砂土層內(nèi)摩擦角與紅土層的差異并不顯著,碎屑層的內(nèi)摩擦角最大,與其它三層差異性顯著。4、黏聚力隨土層深度變深,先增加,再減小,峰值深度在2m左右,隨土層深度變深,黏聚力的變異性也表現(xiàn)為先變大,再減小。內(nèi)摩擦角隨土層深度變深,而出現(xiàn)平緩增加的趨勢(shì),黏聚力的變異性則表現(xiàn)為先變大,再減小。內(nèi)摩擦角的增大對(duì)抗剪強(qiáng)度的增大貢獻(xiàn)量明顯大于黏聚力的消散對(duì)抗剪強(qiáng)度的減小量。5、影響花崗巖殘積土抗剪強(qiáng)度指標(biāo)的主要因素為水分含量以及砂粒含量。在同種土層或不同土層處于外界條件或結(jié)構(gòu)類(lèi)似的情況下時(shí),影響其抗剪性能發(fā)生變異的可能是飽和導(dǎo)水率、最大容重變化量以及土壤干密度。同時(shí)考慮水分和砂粒含量的抗剪強(qiáng)度發(fā)展趨勢(shì)為,在一定含水率范圍內(nèi),抗剪強(qiáng)度隨含水率的降低、砂粒含量的增多而增大,黏聚力總體隨含水率降低而升高,隨砂粒含量的增大而減小,內(nèi)摩擦角總體隨含水率降低而升高,隨砂粒含量的增多而增大。影響抗剪強(qiáng)度指標(biāo)趨勢(shì)面發(fā)生震蕩的原因很可能是孔隙氣水壓力的突變,土壤膠結(jié)物對(duì)花崗巖殘積土的抗剪強(qiáng)度影響可能被高估。
[Abstract]:Granite residual soil is widely distributed in the South China, formed in the granite residual soil on the slope collapse, landslide is an important type of soil erosion in the south. The granite residual soil has inhomogeneity and anisotropy, significant softening, disintegration, is a kind of special soil structure. Taking Hubei Province Tongcheng County typical development, clear layers (surface layer, clay layer, sand layer, debris layer) of the granite residual soil, three axis consolidated undrained test and quick direct shear experiment, study basic properties, combined with different layers of granite residual soil: 1 different soil stress-strain relationship were strain hardening type, show plastic failure, for the same kind of soil, 4 kinds of confining pressure, the stress-strain curve of pitch are more obvious; the clay and sand layer in the initial strain, the deviatoric stress changes influenced by the confining pressure is smaller, and the strain level is closely related; under the same confining pressure Small, partial surface damage should force required, while the detritus layer damaged by partial stress is larger. The effect of capillary porosity pore pressure of the soil to a certain extent, failure ratio Rf coefficient of variation and capillary water capacity is a significant correlation between the changes of capillary porosity, is the impact of soil damage than Rf mutation causes that is, the pore mutations affecting soil failure ratio changes.2 to some extent, the granite residual soil softening is very significant, the 4 layer soil internal friction angle and cohesion were first increased and then decreased, the cohesion peak in the average moisture content of 8.11%, 11.76% average water friction angle the peak in the rate of water content in around 10%, the granite residual soil shear strength may be obtained with the maximum value, when more than a certain water content, with the increase of granite residual soil water content, the strength is remarkably reduced. The cohesion quickly dissipated, the internal friction angle decreased, significantly reduce the internal friction angle of the strength reduction may be the main reason. The granite residual soil porosity, too much water to disperse soil particles, reduce the contact interaction between.3 particles and in water content (average 23.98%) no significant different conditions (p0.5), cohesion clastic soil layer for significantly lower than the other three layer, surface layer, clay layer, sand layer between the cohesion of the difference was not significant. The cohesion in the topsoil and the debris layer variation of friction angle variation are smaller in clay and sand layer and the variation of.4 soil layer in the surface layer of the internal friction angle of the minimum value, the distribution is more concentrated, there is no significant difference between the clay layer and the adjacent layer of clay. The internal friction angle in the middle level, only showed significant difference and detrital layer, this may be due to sand layer The particle size distribution, density, cementation, void condition etc in the cause of moderate level. The internal friction angle and the difference of sand clay layer is not significant, the internal friction angle of the largest debris layer, and the other three layers.4 significant difference, cohesion with soil depth increases, increased first and then decreased. That peak at about 2m depth, with soil depth increases and variability of cohesion as well as to get bigger, and then decreased. The internal friction angle with the soil depth becomes deeper, and the emergence of slowly increasing trend, the variability of the cohesion was larger, and a small amount of.5 reduction of internal friction decreases. Angle increases the shear strength increases with volume was significantly higher than the dissipation against cohesion shear strength. The main factors affecting the granite residual soil shear strength index for water content and sand content. In the same soil or soil in different external conditions or structure in a similar situation When the possible influence the shear performance variation is saturated hydraulic conductivity, bulk density and maximum dry density of soil. Considering the shear strength of the development trend of water and sand content, water content in a certain range, the anti shear strength decreased with increasing water content, increasing sand content increasing. The overall cohesion with the water content increased, and decreased with increasing sand content, the internal friction angle with the overall moisture content decreased, and increases with the increase of sand content. The influence of shear strength index concussion reason trend is likely to occur mutation pore gas water pressure, the shear strength may be affected overestimation of soil cement on the granite residual soil.

【學(xué)位授予單位】：華中農(nóng)業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：S157

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