北京典型地面沉降区土体压缩特征研究

A Study on Soil Compression Characteristics in Land Subsidence Areas within Beijing

北京平原区地面沉降目前处于快速发展阶段,影响因素十分复杂,其中粘性土体的存在是其赖以形成的物质基础。以北京昌平八仙庄典型地面沉降区为研究对象,采取逐级加荷、逐级卸荷以及反复加卸荷,分析100 m以浅粘性土体在不同加卸载方式下的固结特征。实验结果表明:荷载从25 k Pa分级加荷到1 600 k Pa,粘土变形量大于粉土,分别为2.822 mm、1.000 mm;荷载从400 k Pa分级卸除到50 k Pa,粘土的回弹量大于粉土,分别为0.277 mm、0.121mm;反复加卸荷条件下粉质粘土及粉土较之粘土更容易达到固结状态,蠕变时间效应为粘土>粉质粘土>粉土。建议在制定地面沉降灾害防治措施方案时,应充分考虑沉降区地层土体特征影响。

Numerous factors are attributed to the rapid development of subsidence in the plain area of Beijing. The existence of cohesive soils in this area provides the material foundation for subsidence, and therefore, this study focuses on the consolidation characteristics of cohesive soils with depth less than 100 m under different loading condition such as progressive loading, progressive unloading, and repeated loading and unloading in a typical subsidence area in Baxianzhuang within the Changping District of Beijing. According to the test results, the deformation of cohesive soils under progressive loading from 25 kPa to 1,600 kPa is greater than that of silt, which is 2.822 mm and 1.000 mm, respectively. The rebound of cohesive soils under progressive unloading from 400 kPa to 50 kPa is also greater than that of silt, which is 0.277 mm and 0.121 mm, respectively; and under repeated loading and unloading condition, silty clay and silt attain a state of consolidation faster than clay; the creep-time effect is sorted as clay〉silty clay〉silt. It is therefore recommended that a full consideration should be given to the effects of soil characteristics in subsidence areas when compiling land subsidence disaster prevention and control plans.