Research On No Vibration Compaction Technology Of Small Spaces Collapsible Loess Foundation

With the continusly deepening of infrastructure construction in loess area,there aremore and more small spaces collapsible loess foundation need to be treated,such astunnel,culvert,building and so on. The treatment of collapsible loess foundation is to limitthe size of the equipment,nor vibration or limited to vibration in those buildings. And theexisting equipment and processing technology can not satisfy this requirement. To dealwith these questions,a new foundation treatment technology is put forward. This researchhas defined the small spaces collapsible loess foundation at first,and analyses thecharacteristic and treatment requirements. Secondly,analysis the compaction of principalstress,the elastic and plastic zone,and the mechanical characteristic laws for compactingdevice of no vibration compacting process through the theory of cavity expansion. Thenthrough the field test by little space no vibration compacting device which is developed byNorthwest Research Institute Co.,Ltd of C.R.E.C,get the radius of influence and treatmenteffect of no vibration compaction. Finally,study the main physical and mechanicalparameters of compaction through Single-hole compacting numerical simulation. The mainresearch contents and acquired results as follows.Firstly,In view of the current foundation treatment technology is not suitable for thesmall space collapsible loess foundation,no vibration compacting technology experimentalstudy was carried out. The test results approve that this technique not only can suitable therequirements of little space collapsible loess foundation treatment,but also has good effect.Secondly,Based on the analysis of pile-hole-soil compaction process of thedeformation and failure,which the pile hole diameter is0.42m. Can obtain the rules ofdeformation and failure of soil around the pile. From the pile to the soil can be divided intothree parts,the first part is failure zone(0~40cm),the second part is plastic zone(40~ 80cm) and the third part is elastic region (more than80cm).Thirdly,no vibration compacting technology processing can eliminate collapsibility,reduce void ratio(void ratio is1.0375to0.7475),increase dry density(dry density is1.34g/cm~3to1.83g/cm~3) of soil between piles. And the foundation bearing capacity isobviously increased,usually can improve140kPa.Finally,based on the study of single-hole compacting numerical simulation,we candraw a conclusion that the monitoring point’s stress,strain and displacement is inverselyproportional to the hole center distance. The maximum influence radius is1.4m ofcompaction. And the orifice is happened uplift damage is usually because of the verticalcomprehensive stress is too large.