振杆密实法处理杂填土地基试验

Field Tests on the Improvement Effect of Miscellaneous Fills Using the Vibratory Probe Compaction Method

城市快速发展所产生的生活、工业和建筑固体废物,通常与天然土体混合堆积形成杂填土。杂填土具有不均匀、欠固结、低强度、高压缩、强湿陷等特性,工程建设中需要进行加固处理。介绍了一项全新技术——振杆密实法在郑州某杂填土地基处理中的应用,通过监测土体水平位移和分层沉降,分析了振杆施工扰动对周围土体的影响;通过施工过程中的地表振动试验,研究了不同工况和不同振动频率下的地表振动响应,确定了各工艺阶段的频率参数,研究了振动能量的传递和衰减规律;通过动力触探、面波等原位测试方法评价了加固效果。结果表明:振杆周围土体深层水平位移大于浅层,而浅层沉降大于深层;留振对扩大水平加固范围的作用有限,浅层土体比深层更易被留振密实;频率对土体振动影响显著,高频时振动集中在垂直方向且幅度较弱,低频时振动以水平和垂直方向为主,且放大效应显著;越接近系统共振频率,水平振动越明显并大于垂直振动。场地共振频率约为16 Hz。振动能量大部分被振源附近土体吸收,安全施工距离小于2 m;加固后土体强度提高1.6倍以上,达到中密状态,满足了加固要求,验证了振杆密实法处理杂填土地基的适用性。

The domestic,industrial,and construction solid wastes are largely produced in the urbanization process.To avoid environment pollution,they are typically mixed with natural soils to form miscellaneous filling foundation.However,miscellaneous filling soil has the characteristics of nonuniformity,underconsolidation,low strength,and high compression and collapsibility,which makes it unfavorable for carrying the upper structure before treatment.In this paper,comprehensive field tests were conducted to study the effect of using the vibratory probe compaction(VPC)method in the treatment of miscellaneous fills.Specifically,the influence of VPC-based construction was analyzed by monitoring the ground deformation(horizontal displacements and layered settlements)and soil responses(velocity,acceleration and frequency)around the probe.Finally,the improvement effect was evaluated using the dynamic penetration and surface wave in-situ tests.The results show that the soil surrounding the vibrating point exhibits significantly lateral extrusion during the penetration stage,which produces horizontal displacements away from the vibrating point.The horizontal displacement of deep soil is greater than that of shallow soil,and the layered settlement of shallow soil is greater than that of deep soil.Although the density of the shallow soil is improved,the prolonged vibration does not expand the horizontal improvement area any more.At high frequencies,the soils vibrate mainly concentrating in the vertical direction and the amplitude is low,while at low frequencies,the soils vibrate mainly concentrating in the radial by vertical direction and the amplitude is high.Moreover,when the frequency being close to the vibrator-probe-soil system resonance frequency the vibration amplitude in the radial direction becomes larger comparing to that in the vertical direction.Based on the analysis of the instantaneous frequency-time law after the Hilbert Transform,the most effective frequency for improving the miscellaneous fills is 16 Hz.Since most of the energy generated by the vibrations is absorbed by the soil near the vibration point,the safe construction distance of the H-probe is less than 2 m.After treatment,the soil strength increases by more than 1.6 times to reach the medium-dense state,indicating the evident effect of VPC method.