Within The Queensland Line Of Lao Li Duan Special Nature Of The Soft Soil And Engineering Measures

Soft soil is fine-grained soil deposited in recent period in the littoral, lake basin bog , valley flat and so on, which has high nature water content, large void ratio , high compressibility, low shearing strength. It distributes and develops widely in the nature. But the forming condition of soft soil developing in the Nei(jiang)-Kun(ming) railway, Lao-Li district, is different from the others. Formed in declivity belt, soft soil is formed from the clay in drift bed, sedentary etc. in common condition of special topographic geomorphic, stratigraphic lithological, hydro-geologic and geographical climate environment etc., rather those formed by standing water or slowly-flowing water. So it has unique composition, texture etc.. Its index of physics and mechanics is close to ordinary soft soil. It has the character of ordinary soft soil, such as high nature water content, large void ratio , high compressibility, bad water permeability , low thixotropy and fluidity, low index of mechanics, bad nature of engineering . Besides, it has complex composition, bad homogeneous large expansibility, strong camouflage and fluidal slip. So it is rather danger to engineering than ordinary soft soil, needed to be taken different measures and method in order to insure engineering stability. After doing a great quantity efforts of survey , exploration , test , experiment and analysis , being based on the detailed check on its characteristic , nature and distribution , and doing experiment in the trial district , it is in fine: binding slope laterally with anti-slide piles for the slope stability ; processing soft soil with crushed break stone pile to form the reunite subgrade for increasing strength of soft soil, and declining soft subgrade settlement; dredging groundwater through the perpendicular and horizontal percolating blind water ditch , to quickly consolidate soft soil, increase strength of soft soil , reduce soil bearing. Summing up above: "strengthening foundation and reinforcing basic" "dealing with soft soil and resisting slide", "dredging groundwater". By the way of construction, observation, check of transport, we can find that there are stable slope, raising strength of soft subgrade, reducing settlement, and descending groundwater level in this district. Every index meets to design demand, makes a better effect, and ensures steady of this railway. According to the objective existence of such a soft soil in nature condition, and having an negative effect on relevant engineering, while this soft soil has not been included in all kinds of codes by now, so we suggest adding declivity soft soil and relate content in the relevant codes, and definition such a soft soil as a clay that is formed by genesis of drift bed, sedentary etc. but not by standing water or slowly-flowing water in declivity belt, its gradient of base subgrade is larger than 10 degrees, and its various index are close to the ordinary soft soil.