珠江三角洲一高速公路软基处理实例分析

CASE ANALYSIS OF FOUNDATION TREATMENT FOR SOFT SOIL IN A FREEWAY OF THE PEARL RIVER DELTA

针对珠江三角洲一高速公路穿越厚度不均匀的深厚软基,开始采用砂桩结合砂垫层、土工格栅处治,由于填土速度过快及砂桩本身的特点,路基填土出现开裂;后采用卸除填土,并利用预应力混凝土管桩结合钢塑格栅进行处治。通过对整个过程的沉降、侧向位移、孔隙水压力等现场观测数据进行分析,得出在厚度不均匀的深厚软基路段不宜采用无抗剪强度的砂桩处理,宜采用具有一定抗剪强度的处治措施,且加载过程应该采用“薄层轮加法”填筑,确保地基的稳定性。

When one freeway goes through uneven soft soil area with great depth in the Pearl River Delta,sand pile,sand bed course and geogrid are adopted firstly to consolidate the soft soil groundsill.During the loading processt,he speed of filling was faster than the allowable one,but the sand pile is without shear strength.So cracks were found on the surface of subgrade filling.In order to keep the stability of groundsill,prestressed concrete tube pile with steel geogride were then used to consolidate the soft soil after the filling was unloaded.The vertical drainage function of sand soil and transverse drainage function of sand bed course were brought to reduce the excessive pore water pressure during the prestressed concrete tube pile was driven into the soft soil.After using tube pile,the stability of groundsill was enhanced,and the filling speed was expedited to guarantee subgrade construction completion before rainy season.With the settlement analysis,the lateral deformation,in-situ pore water pressure,and the invalidation reason of sand pile are achieved.The conclusions that sand pile without shear strength is not suitable for deep soft soil treatment at slope foot and that the measurement with certain shear strength can be adopted are acceptable.In order to guarantee the stability of groundsill,rotational folium loading shall be adopted during loading process.