Mechanical behavior of soft clay improved with lime cloumn during vertical excavation

研制了一种可模拟飞行开挖过程的离心挖掘机，对软土在离心挖掘机开挖过程中的力学行为进行了研究。本研究进行了三个系列的离心试验。在第一个系列中，通过离心模型试验研究了不排水强度随深度增加对垂直切口稳定性的影响，在离心模型试验中，通过增加离心加速度使制备好的模型失效。在第二个系列中，用挖掘机对正常固结和轻度超固结两种软粘土进行了无支护开挖和带或不带绑扎支护墙的开挖。在开挖过程中，测量了板桩墙的土压力以及墙和粘土的变形。在第三季。主动侧采用石灰桩改良的常固结粘土无支墙开挖。研究了加固效果及加固地基在开挖过程中的力学性能。对试验结果进行分析，得出以下结论：(1)对于强度均匀和强度递增的粘土地基，无粘结板桩墙开挖破坏机理不同。前者在主动侧和被动侧均表现为平移运动，有明显的线性滑移面；后者仅在主动侧表现为绕底倾斜，有明显的线性滑移面。(2)开挖无栓板桩时，在强度均匀的粘土中，埋置不利于稳定。稳定数随埋深和强度的增加而显著增加。(3)活性状态下粘土的特性对板桩墙体的变形和应变起主导作用。4)无扎板桩主动侧采用石灰桩改造，降低了板桩应变和板桩壁主动压力，有效提高了基坑稳定性。少

A centrifuge excavator with which the process of excavation can be simulated in-flight was developed and a study on the mechanical behavior of soft clay during excavation using the centrifuge excavator is reported here. In this study three series of centrifuge tests were carried out. In the first series, the effect of undrained strength increase with depth on the stability of vertical cuts was investigated by centrifuge model tests in which prepared models were brought to failure by increasing centrifugal acceleration. In the second series, unsupported excavation and excavation with a supporting wall with or without ties were conducted with the excavator for two types of soft clay, namely normally consolidated and lightly overconsolidated clays. Earth pressures on sheet pile walls and deformations of the walls and clay were measured during excavation. In the third series. excavation with supporting wall without tie for normally consolidated clay improved with lime piles in active side … More were conducted by using the excavator. The effect of improvement and mechanical behavior of improved groud during excavation were investigated.The analyzes of the test results provided the following conclusions.1)The mechanism of failure in excavation with sheet pile walls without ties is different for clay grounds with uniform strength and increasing strength. For the former the wall shows translational movement with well-defined linear slip surface both in the active and passive side, while for the latter the wall tilts around the bottom with linear slip surface only in the active side.2)In excavation with sheet pile walls without ties, the embedment does not contribute to the stability in clay with uniform strength. but stability number increases significantly with depth of embedment in clay with increasing strength.3)The characteristics of clay in the active state have a dominant effect on the deformations and strains of sheet pile walls.4)The improvement with lime piles in the active side of sheet pile without tie reduces strains of sheet pile and active pressures on sheet pile walls, and in effective in increasing the stability of excavation. Less