單向循環(huán)荷載作用下飽和重塑紅黏土的動力特性

羅文俊 王海洋 馬斌 陳曉飛

摘 要： 為探究長期循環(huán)動荷載作用下紅黏土的塑性累積應變效應，對南昌地區(qū)飽和重塑紅黏土進行單向加載循環(huán)三軸試驗，研究了動應力比、初始孔隙率、固結(jié)圍壓、加載頻率、排水條件對紅黏土塑性累積應變和動孔壓的影響。結(jié)果表明：隨著動應力比的增大，紅黏土變形曲線由漸穩(wěn)型向破壞型過渡;當動應力比小于臨界動應力比時，隨著循環(huán)振次的增加，紅黏土的塑性累積應變和動孔壓發(fā)展曲線均表現(xiàn)為起始快速增長，后出現(xiàn)拐點，最終趨于穩(wěn)定;相同的動應力比下，試樣的累積應變和動孔壓隨初始孔隙率、固結(jié)圍壓的增大而增大，隨加載頻率的增大而減小，不排水條件下的累積應變要大于排水條件下的累積應變;塑性累積應變越大，應變發(fā)展曲線拐點出現(xiàn)越滯后;隨著動應力比的增大，土體的軟化程度也越大，但在較高的循環(huán)振次下，軟化程度減弱。

關(guān)鍵詞： 重塑紅黏土;動力特性;循環(huán)荷載;三軸試驗;累積應變;動孔壓比

中圖分類號：TU435? ? 文獻標志碼：A? ?文章編號：2096-6717（2020）02-0001-09

Dynamic characteristics of saturated remodeling red clay under uniaxial cyclic loading

Luo Wenjun1， Wang Haiyang1， Ma Bin2， Chen Xiaofei2

（1.School of Civil Engineering and Architecture， East China Jiaotong University， Nanchang 330013， P.R.China; 2.China Railway Second Bureau Group Co.， Ltd.， Chengdu 610000， P.R.China）

Abstract：? In order to explore the plastic cumulative strain effect of red clay under long-term cyclic dynamic load， saturated remolded red clay in Nanchang area was used for cyclic triaxial test under uniaxial loading.The effects of dynamic stress ratio， initial porosity， consolidation confining pressure， loading frequency and drainage conditions on plastic cumulative strain and dynamic pore pressure of red clay were studied.The results of tests indicate that：with the increase of dynamic stress ratio， the deformation curve of red clay transits from gradual stable type to destructive type.When the dynamic stress ratio is less than the critical dynamic stress ratio， with the increase of cyclic vibration times， the plastic cumulative strain and dynamic pore pressure development curves of red clay both show initial rapid growth， and then the inflection points appear and finally tend to be stable.Under the same dynamic stress ratio， the cumulative strain and dynamic pore pressure of the sample increase with the increase of initial porosity and consolidation confining pressure， and decrease with the increase of loading frequency.At the same time， the cumulative strain under undrained condition is larger than that under drained condition.The larger the plastic cumulative strain is， the later the inflection point of strain development curve appears.With the increase of dynamic stress ratio， the softening degree of the soil increases， but at higher cyclic vibration times， the softening degree decreases.

Keywords： saturated remolded red clay; dynamic characteristics; uniaxial cyclic load; dynamic triaxial test; cumulative strain; dynamic hole pressure ratio

紅黏土是一種呈棕紅、褐黃等色的特殊黏性土，在江西、湖南、廣西等濕熱多雨地區(qū)皆有廣泛分布。隨著鐵路交通事業(yè)的飛速發(fā)展，很多地段都需要用紅黏土作為路基填料，紅黏土具有弱膨脹性、壓縮性低、結(jié)構(gòu)連接強度高的特點，用作鐵路路基填料可以帶來很高的經(jīng)濟效益[1]。近年來，鐵路逐漸向高速、重載方向發(fā)展，在長期循環(huán)荷載作用下，紅黏土路基產(chǎn)生變形和不均勻沉降，嚴重影響了列車運行的安全性和舒適性。……