Model Test For Singel Jacked Pile And Grouting Surrounding Pile In Sandy Soil

Because of no noise, no vibration ,high construction speed and reliable quality , the jacked pile are more widely applied in multi-storey buildings and high-rise buildings in China's soft soil area. In recent years, with its popularization and application in the north of china , it is found that it is difficult for jacked pile to cross the middle and thick sand and hard soil in rivers and lakes'sedimentary area. When the force is small the pile can't be pressed downward , however when it's increased the pile always be broken easily.For current commonly used auxiliary methods ,such as watering and digging ,will reduce the jacked pile's compaction effect . When the pile into the sand bearing stratum, because of sand's "enhanced" and "relaxation" effect ,the resistance will increase with the growth of pressure and decreases while unloaded, which has brought two major issues those are instability bearing capacity and not easily controlled construction quality. So sometimes in order to overcome these shortcomings , drilling piles and post-grouting piles are used. However it is difficult to drilling in sand soil area, and it bringing lot of questions , such as drill stuck,drill dropped, hole wall collapses, which make the drilling pile isolated, broken, mudded, necked and make its quality can't been guaranteed. And the most important is that the drilling pile not only haven't compaction effects while holing , but also it cannot eliminate the sand liquefaction and loess collapsibility. Grouting pile can be eliminated bottom sediment question and improve pile's bearing capacity and meet the demand of deformation, but the drilling pile's bearing capacity is more lower than that of design capacity, resulting to a huge waste.In view of this, the method is proposed that installation and grouting are conducted at the same time, which belongs to the field of precast pile driving construction technology in the area of architecture. The main technical features are: the slurry are configured at first, then static piles and grouting process are executed simultaneously. In the time of pressing the pile , the grout are inject into the soil. When the pile tip reaches the design depth, then continue to inject grout into the pile, so that the pile head expand. This method reduces the construction costs and improve the quality of construction and overcome the difficulties of jacked pile's shortcomings. This method's application will reduce the dynamic friction and improve the efficiency of piling, and improve the latter part of pile shaft resistance, tip resistance, ultimate bearing capacity and reduce settlement. This techinology not only ensure the depth and pile quality, but also reduce the machine's pressure, improve construction efficiency, thus extending the scope of application of jacked pile and reduce project cost.Therefore, this article relies on Shanxi Province Natural Science Foundation project "Synchronous Dynamic grouting method to reduce jacked pile resistance and improve the bearing capacity of piling mechanism of experimental study" (item number: 2008011055), in order to study the working mechanism of jacked pile and its grouting, by carrying out a series of model tests in the sand, including different pile diameter, different pile materials, different slurry ratio, grouting and non-grouting contrast, this paper have the following conclusions:1. Under the same conditions, after grouting when punching process,the piling force and dynamic side friction resistance all reduce compared to the situation of without grouting。2. Under the same conditions, enlarging pile's diameter and increasing pile's stiffness can decrease the settlement and improve ultimate bearing capacity .3. Under the same conditions, the settlement decrease with the enhancement of sand recovery ,while the pile side friction resistance and ultimate bearing capacity are improve during the static load test.4. Under the same conditions, with the slurry setting time increases, the settlement reduced ,while the friction resistance and ultimate bearing capacity of pile are improved during the static load test.5. Under the same conditions, after grouting, the settlement significantly reduce and the friction resistance and ultimate bearing capacity significantly increases compared to the situation of without grouting during the static load test.