本文選題：崩崗 + 無(wú)側(cè)限抗壓強(qiáng)度��； 參考：《華中農(nóng)業(yè)大學(xué)》2017年碩士論文

【摘要】：崩崗是中國(guó)南方熱帶、亞熱帶花崗巖低山丘陵地區(qū)水土流失的一種特殊類型。崩崗侵蝕的發(fā)生發(fā)展與其巖土體力學(xué)性質(zhì)有著密切的聯(lián)系,由于花崗巖風(fēng)化殼土體疏松深厚,且內(nèi)部存在軟弱結(jié)構(gòu)面,并伴隨有大量的原生節(jié)理和構(gòu)造裂隙,導(dǎo)致崩崗巖土特性差異明顯,因此,崩崗不同層次巖土體力學(xué)性質(zhì)不穩(wěn)定。崩崗崩壁巖土體在無(wú)側(cè)向約束的條件下,抵抗軸向壓力發(fā)生剪切破壞的極限強(qiáng)度稱為無(wú)側(cè)限抗壓強(qiáng)度,是反映土體力穩(wěn)性的一項(xiàng)重要指標(biāo)。因此,有必要對(duì)崩崗巖土體無(wú)側(cè)限抗壓強(qiáng)度進(jìn)行系統(tǒng)性研究,這對(duì)于豐富和完善崩崗巖土體力學(xué)性質(zhì)具有重要的指導(dǎo)意義。目前,崩崗侵蝕的治理中多采用工程措施和生物措施相結(jié)合的方法,但關(guān)于新工藝和新技術(shù)卻應(yīng)用不足,同時(shí)由于崩崗巖土體粘結(jié)性差,且在現(xiàn)實(shí)中存在劇烈的干濕變化,極易導(dǎo)致崩崗崩壁失穩(wěn)坍塌。因此,有必要對(duì)崩崗巖土體進(jìn)行適當(dāng)改良,以提高崩崗?fù)馏w強(qiáng)度和穩(wěn)定性。本文以湖北省咸寧市通城縣典型崩崗作為研究對(duì)象,通過(guò)野外調(diào)查與室內(nèi)試驗(yàn)相結(jié)合的方法,分別開(kāi)展典型崩崗不同層次巖土體基本特性研究,揭示崩崗侵蝕成因的物質(zhì)基礎(chǔ);制備重塑土試樣研究崩崗不同層次巖土體無(wú)側(cè)限抗壓強(qiáng)度,探討干密度和含水率以及干濕循環(huán)效應(yīng)對(duì)無(wú)側(cè)限抗壓強(qiáng)度的影響;利用黃麻纖維和石灰對(duì)崩崗不同層次巖土體進(jìn)行改良研究,探討改良崩崗巖土體無(wú)側(cè)限抗壓強(qiáng)度的變化規(guī)律。得到相關(guān)研究結(jié)果如下:(1)崩崗?fù)馏w容重的變化規(guī)律為碎屑層斑紋層紅土層表土層;總孔隙度的變化規(guī)律為碎屑層表土層紅土層斑紋層;土壤機(jī)械組成變化規(guī)律為從紅土層開(kāi)始隨著采樣深度的增加,砂粒含量不斷增加,而黏粒含量則不斷減少;紅土層液塑限含水量均為最大,而碎屑層液塑限含水量均為最小;土壤有機(jī)質(zhì)含量隨著土層深度的增加而顯著減少,其中碎屑層有機(jī)質(zhì)含量極少;崩崗?fù)馏w的pH值均較低,呈酸性;碎屑層陽(yáng)離子交換量最小;而游離氧化鐵含量則存在明顯差異。(2)崩崗?fù)馏w無(wú)側(cè)限抗壓強(qiáng)度隨著含水率的增加呈先增加后減小的趨勢(shì),且出現(xiàn)最大值時(shí)的含水率都在15%或20%左右;隨著干密度的增加,無(wú)側(cè)限抗壓強(qiáng)度先緩慢增加后呈近似線性減小,且減幅較大,出現(xiàn)最高值時(shí)的干密度均為1.30 g/cm3左右;干密度和含水率對(duì)崩崗巖土體無(wú)側(cè)限抗壓強(qiáng)度產(chǎn)生了明顯的交互效應(yīng),在等值線圖中可分為三個(gè)區(qū)域:干密度主效應(yīng)區(qū)、含水率主效應(yīng)區(qū)、干密度和含水率交互效應(yīng)區(qū),在三維曲面圖存在“山谷”、“山峰”、“山脊”等曲線形態(tài)。(3)崩崗?fù)馏w的無(wú)側(cè)限抗壓強(qiáng)度均隨著干濕循環(huán)次數(shù)的增加而逐漸衰減,直至最后趨于穩(wěn)定,其變化規(guī)律大致分為3個(gè)階段:急速衰減、減速衰減、衰減穩(wěn)定,其中在第1次干濕循環(huán)后衰減幅度最大,分別為26%、15%、40%和49%,在第2~4次干濕循環(huán)后衰減幅度逐漸減小,在第5次干濕循環(huán)后基本保持不變;隨著干濕循環(huán)次數(shù)的增加,崩崗?fù)馏w無(wú)側(cè)限抗壓強(qiáng)度總體表現(xiàn)為表土層紅土層斑紋層碎屑層。崩崗?fù)馏w無(wú)側(cè)限抗壓強(qiáng)度與干濕循環(huán)次數(shù)之間呈現(xiàn)較好的指數(shù)函數(shù)關(guān)系,且在通過(guò)考慮崩崗不同層次土體深度比和干濕循環(huán)次數(shù)的共同影響下,建立無(wú)側(cè)限抗壓強(qiáng)度的預(yù)估模型。(4)通過(guò)對(duì)崩崗?fù)馏w的正交試驗(yàn)設(shè)計(jì),初選出黃麻纖維的最優(yōu)加筋條件,其中表土層:加筋長(zhǎng)度15 mm、加筋率0.35%、整體加筋;紅土層:加筋長(zhǎng)度15 mm、加筋率0.25%、上部加筋;砂土層:加筋長(zhǎng)度15 mm、加筋率0.35%、整體加筋;碎屑層:加筋長(zhǎng)度15 mm、加筋率0.30%、下部加筋;黃麻纖維加筋土的應(yīng)力-應(yīng)變曲線變化規(guī)律可分為3個(gè)階段:急速衰減階段、減速衰減階段、衰減穩(wěn)定階段。在最優(yōu)加筋條件下崩崗?fù)馏w的無(wú)側(cè)限抗壓強(qiáng)度分別提高了27.81%、29.73%、23.26%、39.58%。(5)采用響應(yīng)面設(shè)計(jì)優(yōu)化得出摻灰率、齡期、含水率三者最佳配比組合。表土層:摻灰率8.99%、齡期28 d、含水率25%;紅土層:摻灰率8.98%、齡期28 d、含水率25%;斑紋層:摻灰率5.84%、齡期18 d、含水率20%;碎屑層:摻灰率6.58%、齡期28 d、含水率23%。(6)在今后的崩崗治理工作中,應(yīng)考慮改良材料的組合使用以提高崩崗巖土體的力學(xué)性能,黃麻纖維是一種成本低且綠色環(huán)保的改良材料,可在崩崗表土層和紅土層治理工作中加以利用,以提高土體強(qiáng)度;而石灰是一種效果明顯且施工方便的改良材料,可在崩崗斑紋層和碎屑層治理工作中加以利用。
[Abstract]:Avalanche is a special type of soil erosion in the low mountain and hilly region of tropical granite in southern China. The occurrence and development of the landslide erosion is closely related to the mechanical properties of rock and soil, because the soil of the granite weathering crust is loose and deep, and there is a weak structural surface in the interior, and there are a large number of primary joints and structural fractures. Therefore, the mechanical properties of rock and soil in different layers are not stable. Under the condition of no lateral constraint, the ultimate strength of the rock and soil body of the collapse and avalanche is called the unconfined compressive strength, which is an important index to reflect the stability of the earth's physical strength. Therefore, it is necessary to take the landslides. The systematic study of unconfined compressive strength of soil is of great guiding significance for enriching and perfecting the mechanical properties of the rock mass. At present, many methods are used to combine the engineering measures and biological measures in the treatment of the landslide erosion, but the new technology and new technology are not applied, at the same time, the cohesiveness of the landslides is poor. There is a severe dry and wet change in reality, which is very easy to cause the collapse of the collapse and collapse of the wall. Therefore, it is necessary to improve the soil strength and stability of the landslide soil. This paper takes the typical landslides in Tongcheng County of Xianning City, Hubei as the research object, through the method of combining field investigation and indoor test, respectively. The basic characteristics of rock and soil soil at different levels of the typical landslides were carried out to reveal the material foundation of the causes of the erosion, and the remolded soil samples were prepared to study the unconfined compressive strength of rock and soil soil at different levels of the landslides, and to explore the effect of dry density, moisture content and dry and wet cycle on the unconfined compressive strength. The same layer of rock and soil soil is improved to study the change law of the unconfined compressive strength of the soil of the improved rock mass. The results are as follows: (1) the change law of the bulk density of the landslides is the clastic layer red soil layer soil layer; the variation law of the total porosity is the red soil layer of the clastic layer soil layer, and the change of soil mechanical composition With the increase of the depth of the red soil, the content of sand increases with the increase of the sampling depth, while the content of clay particles is decreasing, and the water content of the clay layer is the largest, while the plastic limit water content of the clastic layer is the smallest, and the soil organic matter content decreases with the increase of the depth of the soil layer, and the content of the organic matter in the clastic layer is very small; The pH value of the soil soil is low and acidity, and the amount of free iron oxide in the clastic layer is the smallest, while the content of free iron oxide is obviously different. (2) the unconfined compressive strength of the sentry soil increases first and then decreases with the increase of water content, and the water content of the maximum value is about 15% or 20%. With the increase of dry density, the unconfined limit is unconfined. The compressive strength increases slowly first and decreases approximately linearly, and the decrease is larger. The dry density of the highest value is about 1.30 g/cm3, and the dry density and water content have obvious interaction effect on the unconfined compressive strength of the rock mass, and can be divided into three regions in the contour map: the main effect area of dry density, the main effect area of water cut, dry There are "valleys", "mountain peaks", "ridge" and other curvilinear forms in the three-dimensional surface maps. (3) the unconfined compressive strength of the landslides gradually attenuates with the increase of the number of dry and wet cycles, until finally tends to stability, and its variation rules are roughly divided into 3 stages: rapid attenuation, deceleration attenuation and attenuation. After first dry and wet cycles, the attenuation amplitude is the largest, which is 26%, 15%, 40% and 49% respectively. After the 2~4 dry wet cycle, the attenuation amplitude decreases gradually. After the fifth dry and wet cycles, the attenuation range is basically kept unchanged. With the increase of the dry and wet cycle times, the unconfined resistance to pressure of the landslide soil body is generally expressed as the red soil layer clastic layer of the soil layer. There is a good exponential function relationship between the unconfined compressive strength of the landslide soil and the number of dry and wet cycles, and the prediction model of unconfined compression strength is established under the influence of the depth ratio of soil mass and the number of dry and wet cycles in different levels of the landslide. (4) through the orthogonal design of the landslide soil, the jute fiber was first selected. Optimum reinforcement conditions, in which the topsoil layer: reinforcement length 15 mm, reinforcement ratio 0.35%, overall reinforcement; laterite: reinforcement length 15 mm, reinforcement ratio 0.25%, upper reinforcement; sand layer: reinforcement length 15 mm, reinforcement ratio 0.35%, integral reinforcement; detrital layer: reinforcement length 15 mm, reinforcement ratio 0.30%, lower reinforcement; jute fiber reinforced soil stress strain curve change The law can be divided into 3 stages: rapid attenuation stage, deceleration and attenuation stage, and attenuation stability stage. Under the optimal reinforcement conditions, the unconfined compressive strength of the landslide soil soil is increased by 27.81%, 29.73%, 23.26%, 39.58%. (5), using the response surface design optimization to get the best mixture ratio, age and water content three. Topsoil layer: ash blending ratio 8.99%, Age 28 d, water content 25%, red soil layer: lime content 8.98%, age 28 d, water content 25%, striped layer: ash mixing rate 5.84%, age 18 D, water content 20%; detrital layer: ash mixing rate 6.58%, age 28 d, water content 23%. (6) in the future of the collapse of the work, should consider the combination of improved materials to improve the mechanical properties of the rock mass, jute fiber is A modified material with low cost and green environment can be used in the treatment of the soil layer and the red soil layer to improve the soil strength, and the lime is a kind of improved material with obvious effect and convenient construction, which can be used in the treatment of the landslides and debris layer and debris layer.
【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】：2017
【分類號(hào)】：S157.1

【參考文獻(xiàn)】

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