發(fā)布時(shí)間：2018-03-05 06:11

  本文選題：殘余強(qiáng)度　切入點(diǎn)：損傷閥值　出處：《西安科技大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：隨著我國(guó)經(jīng)濟(jì)建設(shè)的發(fā)展,寒區(qū)的巖土工程數(shù)量及規(guī)模不斷擴(kuò)大,凍融災(zāi)害是亟待解決的關(guān)鍵問題。研究巖石在凍融條件下的損傷機(jī)理和破壞條件,可以為有效的指導(dǎo)工程建設(shè)安全生產(chǎn)提供依據(jù)。本文采用宏細(xì)觀方法與統(tǒng)計(jì)學(xué)方法相結(jié)合,對(duì)凍融與荷載條件下巖石的損傷模型及強(qiáng)度準(zhǔn)則進(jìn)行了較為深入的研究。將受荷巖石抽象為損傷和未損傷兩部分材料組成,損傷部分可承受殘余強(qiáng)度的力;基于Weibull統(tǒng)計(jì)分布和Drucker-Prager準(zhǔn)則,建立了可反映巖石殘余段變形特征的損傷模型;利用峰值點(diǎn)法求解得到模型參數(shù)的理論表達(dá)式,并分析其物理意義。針對(duì)目前常用引入修正因子建立的巖石損傷模型,就反映巖石殘余段變形特征的適用性進(jìn)行了對(duì)比,并從數(shù)學(xué)形式上進(jìn)行了分析說明�？紤]凍融因素和荷載因素對(duì)巖石的影響,基于總損傷變量的概念,建立了凍融循環(huán)與荷載共同作用下的巖石損傷模型。分析討論了總損傷變量和總損傷演化率隨圍壓和凍融次數(shù)的變化規(guī)律。當(dāng)凍融循環(huán)次數(shù)增加時(shí),巖石損傷程度加劇,宏觀力學(xué)性能劣化,抗壓強(qiáng)度和殘余強(qiáng)度減小,破壞方式逐漸趨向于延性破壞;當(dāng)圍壓增大時(shí),巖石損傷劣化程度減小,抗壓強(qiáng)度和殘余強(qiáng)度增大,脆性特征逐漸消失,延性特征逐漸明顯。通過分析巖石應(yīng)力應(yīng)變關(guān)系曲線在峰值點(diǎn)處的幾何特征,采用多元函數(shù)求全微分的方法建立了考慮凍融效應(yīng)的巖石強(qiáng)度準(zhǔn)則。該準(zhǔn)則可用于表征不同凍融循環(huán)次數(shù)下巖石在極限狀態(tài)時(shí)內(nèi)部應(yīng)力參量之間的關(guān)系,且能反映強(qiáng)度莫爾包絡(luò)線的曲線性質(zhì)。當(dāng)凍融循環(huán)次數(shù)增多時(shí),強(qiáng)度莫爾包絡(luò)線曲線性質(zhì)更為顯著,表明該準(zhǔn)則適合凍融受荷巖石強(qiáng)度的判定;據(jù)此重新設(shè)定損傷閥值,建立新型凍融受荷巖石的損傷模型。與試驗(yàn)數(shù)據(jù)進(jìn)行對(duì)比分析,結(jié)果表明,新型的凍融受荷模型無法較好的反映巖石塑性屈服階段,但在峰后段和殘余段仍與試驗(yàn)曲線吻合較好。
[Abstract]:With the development of economic construction in China, the number and scale of geotechnical engineering in cold regions are expanding, and freeze-thaw disasters are the key problems to be solved. The damage mechanism and damage conditions of rocks under freezing and thawing conditions are studied. It can provide the basis for guiding engineering construction safety production effectively. This paper combines macroscopical method with statistical method. The damage model and strength criterion of rock under freeze-thaw and load conditions are studied deeply. The loaded rock is abstracted into two parts: damaged and undamaged, and the damage part can bear the force of residual strength. Based on the Weibull statistical distribution and the Drucker-Prager criterion, a damage model reflecting the deformation characteristics of the residual rock is established, and the theoretical expression of the model parameters is obtained by using the peak point method. And its physical significance is analyzed. According to the rock damage model established by introducing correction factor, the applicability of reflecting the deformation characteristics of residual rock is compared. Considering the influence of freeze-thaw factor and load factor on rock, based on the concept of total damage variable, The damage model of rock under the combined action of freeze-thaw cycle and load is established. The variation law of total damage variable and total damage evolution rate with confining pressure and freeze-thaw times is discussed. When the freeze-thaw cycle number increases, the damage degree of rock is aggravated. When the confining pressure increases, the damage deterioration degree of rock decreases, the compressive strength and residual strength increase, and the brittle characteristics gradually disappear, when the confining pressure increases, the compressive strength and residual strength decrease, the failure mode tends to ductile failure, and when the confining pressure increases, the damage degradation degree decreases, the compressive strength and residual strength increase, and the brittle characteristics gradually disappear. By analyzing the geometric characteristics of the stress-strain relationship curve at the peak point, A rock strength criterion considering freeze-thaw effect is established by using multivariate function to solve the total differential equation. The criterion can be used to characterize the relationship between the internal stress parameters of rock under different freezing and thawing cycles under the limit state. When the number of freeze-thaw cycles increases, the properties of intensity-moire envelope curves are more obvious, which indicates that the criterion is suitable for judging the strength of frozen and thawed rocks, and the damage threshold is reset accordingly. A new damage model of frozen and thawed rock is established. The results show that the new model can not reflect the plastic yield stage of rock. But at the back of the peak and the residual section, it still agrees well with the test curve.
【學(xué)位授予單位】：西安科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O346.5

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