侧限条件下压实膨胀土的侧向压力试验研究及简化预测方法

Experimental investigation and simplified estimation approach for lateral stress of compacted expansive soils under K_(0) condition

针对侧限条件(即K_(0)状态)下压实膨胀土在吸湿饱和过程中的侧向压力问题,采用K_(0)固结仪对南阳压实膨胀土开展试验研究,测定:1)竖向荷载σ_(v)与试样浸水饱和后的侧向压力P_(L)和孔隙比e的关系以及饱和试样在一维固结过程中的P_(L)−σ_(v)−e关系;2)不同初始干密度ρ_(d0)以及制样含水率w_(0)条件下等体积浸水饱和过程中试样的侧向压力P_(L)0与竖向压力σ_(v)0的关系;3)当σ_(v)=50 kPa时,ρ_(d0)和w_(0)对P_(L)的影响。探讨压实过程中产生的残余侧压力P_(r)对P_(L)的影响以及侧向膨胀力P_(EX)随σ_(v)的变化规律。研究结果表明:Pr对饱和试样的P_(L)无明显影响;膨胀过程与固结过程中的P_(L)−σ_(v)−e关系呈滞回现象;在膨胀过程中,P_(L)−σ_(v)的关系呈双线性特征,其临界点在P_(L)=σ_(v)处;P_(L),P_(L)0和σ_(v)0均与ρ_(d0)呈线性关系,它们随w_(0)增大先增大后减小,在土体的塑限附近达到峰值;P_(L)0/σ_(v)0随ρ_(d0)和w_(0)增大而增大,说明等体积浸水饱和过程中试样的各向异性特性随ρ_(d0)和w_(0)增大而降低;P_(EX)随σ_(v)增大呈先增大后减小的趋势。基于试验结果,提出预测膨胀土中支挡结构侧向压力的简便方法,该方法能够有效反映膨胀土中支挡结构侧向压力分布的非线性特征。

The lateral stress of compacted expansive soils during soaking under K_(0) condition(i.e.laterally confined condition)was studied.An experimental program was performed on compacted Nanyang expansive soil using K_(0) oedometer to reveal:1)the relationships among vertical stressσ_(v),lateral stress P_(L) and void ratio e upon soaking;2)the influences of initial dry densityρ_(d0) and compaction moisture content w_(0) on the lateral and vertical stresses upon soaking when no swelling strain was allowed(denoted as P_(L)0 andσ_(v)0,respectively);3)the influences ofρ_(d0) and w_(0) on the P_(L) of saturated specimens whenσ_(v)=50 kPa.In addition,the influence of compaction-induced residual lateral stress Pr on P_(L) and the relationships between lateral swelling pressure P_(EX) andσ_(v) were also discussed.The results show that Pr has no apparent influences on the P_(L),the P_(L)−σ_(v)−e relationship during swelling and consolidation which shows hysteretic characteristics,and the P_(L)−σ_(v) relationship during swelling is bilinear and the turning point is at P_(L)=σ_(v).P_(L),P_(L)0 andσ_(v)0 increase linearly with the increase ofρ_(d0).However,they initially increase with the increase of w_(0) but decrease with the further increase in the w_(0) and thus reaches a peak at the soil's plasticity limit.P_(L)0/σ_(v)0 increases with the increase ofρ_(d0) and w_(0),indicating that the anisotropy of the specimens decreases with the increase ofρ_(d0) and w_(0) during constant volume soaking.The P_(EX) first increases with the increase ofσ_(v) but decreases with the further increase of theσ_(v).Based on the experimental results,a simple approach is proposed to estimate the distribution of the lateral stress on retaining structures in expansive soils,which reliably represents the nonlinear characteristics of distribution of the lateral stress.