Abstract
Based on analysis of the formation mechanism and characteristics of the negative friction in collapsible loess areas, this study investigates the load transfer law of a wall-soil system under a vertical load, establishes the vertical bearing model of a lattice diaphragm wall, and analyzes the vertical bearing capacity of an assembled latticed diaphragm wall (ALDW) in a loess area. The factors influencing the vertical bearing characteristics of the ALDW in a loess area are analyzed. The vertical bearing mechanism of the lattice diaphragm wall in the loess area is investigated. The failure modes of the ALDW in the loess area are mainly shear failure of the soil around the wall and failure of the wall-soil interface. In the generation and development of negative friction, there is always a point where the relative displacement of the wall-soil interface is zero at a certain depth below the ground; at this point, the wall and soil are relative to each other. The collapsibility of loess, settlement of the wall and surrounding soil, and rate and method of immersion are the factors affecting the lattice diaphragm wall. The conclusions of this study provide a reference for the design and construction of ALDWs in loess areas.
Highlights
In the excavation stage of a foundation pit, the lattice diaphragm wall is used as an enclosure structure and seepage control structure
Because the lattice diaphragm wall has very high strength and individual vertical bearing capacity, it can directly bear the vertical load of the upper structure as part of the main structure or as the main structure itself. e lattice diaphragm wall can play a role in the enclosure structure during the construction period, while it can play the role of vertical support in the use stage
Advances in Civil Engineering wall retaining structure is similar to that of a gravity retaining structure based on deformation data measured for a dock foundation pit. e field monitoring data reported by Liang et al [9] showed that the ratio of the horizontal displacement of the lattice wall to the excavation depth of the foundation pit was between 0.15% and 0.50%, and the horizontal displacement of the lattice wall was significantly lower than that of a tension anchor diaphragm wall
Summary
Friction, q, and acts on the wall, causing the end of the wall to sink into the soil by δl; the end resistance, Qb, plays a role. e soil near the end of the wall shows a positive friction, q, as shown in Figure 3(a). e contribution of the wall compressive deformation to the wall top displacement under negative friction is δf (including the total displacement, δ0, of the wall top sinking through deformation). e movement of the soil relative to the wall is zero at vertical position ln; that is, the neutral point is located there. e displacement of the decomposed wall and the corresponding lateral resistance are shown in Figures 3(b) and 3(c). E movement of the soil relative to the wall is zero at vertical position ln; that is, the neutral point is located there. During the generation and development of negative frictional resistance, there always exists a point at a certain depth below the ground at which the relative displacement between the wall and soil is zero. E soil moves downward relative to the wall in the section above this point, and the wall is subjected to a negative frictional resistance. E neutral point has three distinct characteristics: the relative displacement of the wall and soil at this point is zero, the friction resistance is zero, and the axial force is the maximum. The position of the neutral point moves downward with time; if the settlement of the soil is completed before the wall sinks, the neutral point will move upward. The core soil, inner and outer longitudinal walls, and wall end soil of the diaphragm wall in a loess area bear the upper load together. erefore, the vertical bearing capacity, Qu, of the lattice diaphragm wall in a loess area is mainly composed of five parts: the side friction, Qs, provided by the lateral soil; negative friction, Qf, of the collapsible loess; side friction, Qsi, provided by the core soil; negative friction, Qfi, of the collapsible loess; and end resistance, Qp, of the lattice diaphragm wall. e vertical bearing capacity can be expressed as follows: δ0
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