發(fā)布時間：2018-03-01 00:08

  本文關(guān)鍵詞： 巖石蠕變 一級加載 蠕變變形 時間效應(yīng) 聲發(fā)射監(jiān)測　出處：《江西理工大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：針對地下結(jié)構(gòu)處于一種常荷載狀態(tài)下經(jīng)過長期蠕變最終導(dǎo)致失穩(wěn)破壞的現(xiàn)象,基于單軸壓縮條件對砂巖進行一級加載狀態(tài)下的蠕變聲發(fā)射試驗,研究了砂巖在蠕變過程中的軸向、橫向與體積變形規(guī)律,進一步研究了蠕變應(yīng)力、擴容點應(yīng)力之間的比值(β值)與蠕變破壞時間的關(guān)系;最后,利用聲發(fā)射技術(shù)對砂巖在不同蠕變階段的聲發(fā)射參數(shù)進行了分析研究。主要得到以下結(jié)論:(1)砂巖在蠕變過程中的橫向蠕變進入減速與加速蠕變階段的時間及變形量都要比軸向蠕變高,且體積擴容效應(yīng)顯著;巖石粒徑越小、越均值,則砂巖越不容易發(fā)生蠕變變形;砂巖在蠕變過程中的損傷主要發(fā)生在減速與加速蠕變階段;單軸壓縮試驗得到的平均擴容點應(yīng)力可作為初步擬定蠕變應(yīng)力水平的依據(jù)。(2)砂巖蠕變應(yīng)力、擴容點應(yīng)力之間的比值(β值)與蠕變破壞時間的關(guān)系表現(xiàn)為:隨著β值的增加,蠕變破壞時間則逐漸減小。(3)聲發(fā)射信號與蠕變速率呈現(xiàn)出正比的關(guān)系,表現(xiàn)為在減速蠕變階段時,聲發(fā)射信號隨著時間的增加而逐漸減小;在等速蠕變階段時,聲發(fā)射信號大致處于較為平穩(wěn)的狀態(tài),其頻度與幅度較小;在等速與加速蠕變交界處,聲發(fā)射信號出現(xiàn)大幅度的“突升”現(xiàn)象,但進入加速蠕變階段后又很快下降并緩慢增長,但其頻度與幅度均要高于前兩個階段;在蠕變破壞時,聲發(fā)射信號大幅度、集群式的增長。聲發(fā)射∑N/∑E(簡稱聲發(fā)射r值)在減速蠕變階段的值普遍要高于等速蠕變階段,且在等速蠕變階段時,聲發(fā)射r值較為平穩(wěn);在加速蠕變階段時,聲發(fā)射r值明顯下降,且在蠕變破壞時,降至最低水平。結(jié)合聲發(fā)射參數(shù)與聲發(fā)射r值在不同蠕變階段的變化特征,在一定程度上可以對砂巖蠕變破壞進行預(yù)測與預(yù)判。(4)軸向應(yīng)變曲線在減速與等速蠕變階段時出現(xiàn)了“突變”的現(xiàn)象,這些“突變”經(jīng)過短暫的調(diào)整后,仍能恢復(fù)穩(wěn)定狀態(tài),此時的聲發(fā)射信號出現(xiàn)了“突升”的現(xiàn)象,這表明巖石內(nèi)部材料強度較低的地方發(fā)生了破裂,但對試樣整體并未構(gòu)成明顯的損傷,聲發(fā)射r值出現(xiàn)較小幅度的降低也正好說明了這一點。因此,聲發(fā)射信號及r值能較好地描述巖石變形和損傷演化規(guī)律。
[Abstract]:Aiming at the phenomenon that the underground structure is under a constant load state, the creep acoustic emission test of sandstone under the first loading condition is carried out based on uniaxial compression condition. The law of axial, transverse and volume deformation of sandstone during creep is studied, and the relationship between creep stress, the ratio of stress at expansion point (尾 value) and creep failure time is further studied. The acoustic emission parameters of sandstone in different creep stages are analyzed by acoustic emission technique. The following conclusions are obtained: 1) the time and deformation of sandstone lateral creep entering deceleration and accelerating creep stage during creep process. The amount is higher than the axial creep, The smaller the grain size of rock, the less the mean value, the less the sandstone is liable to creep deformation, and the more the damage of sandstone is in the stage of deceleration and accelerated creep. The average expansion point stress obtained by uniaxial compression test can be used as the basis for preliminary determination of creep stress level. The relationship between the ratio of expansion point stress (尾 value) and creep failure time is as follows: with the increase of 尾 value, On the other hand, the creep failure time decreases gradually) the acoustic emission signal is proportional to the creep rate, which decreases gradually with the increase of time during the deceleration creep stage, and at the constant velocity creep stage. The acoustic emission signal is in a relatively stable state, and its frequency and amplitude are relatively small. At the junction of constant velocity and accelerated creep, the acoustic emission signal appears a large "sudden rise" phenomenon, but after entering the accelerated creep stage, the acoustic emission signal decreases quickly and increases slowly. However, its frequency and amplitude are both higher than those of the first two stages, and the acoustic emission signal increases by a large margin during creep failure, and the acoustic emission 鈭，

本文編號：1549542