黄土地场自重湿陷量实测值与计算值差异的原因分析

在兰州和平镇做了一大型现场浸水试验，测定了场地自重湿陷量，并利用实验数据计算了其湿陷量。现场浸水试验时，必须考虑浸水时间和入渗深度的影响，当湿润峰未到达湿陷性土层底面时，则存在很大一部分剩余湿陷量，由此低估了实际湿陷量。该现场浸水试验湿陷土层深度24 m，浸水61天，湿润峰深度达到12 m左右。按平均下渗速率估算，达到湿陷土层底面，需要120天以上。在湿陷性土层完全浸水的情况下，兰州地区大厚度湿陷性黄土的实测值远大于计算值，二者的比值为2.0左右，大于规范给出的修正系数1.5。综上所述，在现场试验时，除确定试验场地地貌单元、湿陷土层厚度外，必须给定合理的浸水时间，以便使湿陷性土层充分湿陷，或浸水后，及时测定湿润峰深度，计算实际湿陷土层的湿陷量，以便得出更合理的修正系数。

Reason Analysis for the Difference between Measured and Calculated Self-weight Collapsibility of the Loess

A large-scale field water immersion test has been carried out in Heping Town, Lanzhou, the self-weight collapsibility of the site has been measured in this paper, and the amount of collapsibility has been calculated by using the experimental data. The influence of immersion time and infiltration depth must be considered in the field water immersion test. When the wetting peak does not reach the bottom of collapsible soil, there will be a large part of residual collapsibility, which underestimates the actual amount of collapsibility. In this field immersion test, the depth of collapsible soil layer is 24m, the depth of wetting peak is about 12m, and the depth of wetting peak is about 12m. According to the estimation of average infiltration rate, it will take more than 120 days to reach the bottom of collapsible soil layer. Under the condition of full immersion of collapsible soil layer, the measured value of large thickness collapsible loess in Lanzhou area is much larger than the calculated value, and their ratio is about 2.0, which is greater than the correction coefficient of 1.5 given in the investigation specification. In conclusion, in the field immersion test, in addition to determining the landform unit of the test site and the thickness of the wet soil layer, a reasonable soaking time must be given in order to fully wet the collapsible soil layer. After flooding, the depth of wetting peak should be measured in time to calculate the actual collapsing amount of soil layer in order to obtain a more reasonable correction coefficient.