Page 247 - 360.revista de Alta Velocidad - Nº 5

Soil stabilization in new railway construction

The results of the following solutions can be highlighted:

• The solution with a layer treated with cement of 25 cm thickness and 6,000 MPa modulus
of elasticity on a 20 cm of soil stabilized with cement, reduces a 34.4% deflections and a
19.8% the value of vertical stress on the upper face of the platform with respect to the
natural soil solution.
• The solution with a layer treated with cement of 25 cm thick and 4,000 MPa modulus of
elasticity on a 20 cm layer of soil stabilized with cement, reduces a 31.1% deflections and
8.88 % the value of vertical stress on the upper face of the platform with respect to the
natural soil solution.
• In case of modifying the thickness, the solution with two layers treated with cement, one
of 20 cm and 6000 MPa module over another stabilized 25 cm thick and 250 MPa module,
decreases a 28.9% deflections and a 2.29% the vertical stress value on the top side of the
platform with respect to the natural soil solution.

7. Conclusions

To carry out a practical assessment, it has been established the comparison of the different
alternatives studied with regard to the usual section in railway superstructure with ballast
(reference solution):
• 30 cm ballast (E = 600 MPa; ν = 0.35)
• 30 cm sub‐ballast (E = 200 MPa; ν = 0.35)

• 40 cm formation layer (E = 100 MPa; ν = 0.35)
• CBR soil > 5 (E = 50 MPa; ν = 0.35)
In the absence of availability of quality aggregates in many areas of Spain, the possibility to
modify this structure by replacing some of its layers made with natural soils by others treated
with lime or cement has been studied. Different thickness and modulus of elasticity has been
analyzed. In any case, the target is that aggregates and soils can ensure the stability of the
superstructure over the passage of an important number of TBR and not be obliged to frequent
maintenance tasks and high cost maintenance.
Acceptable results in comparative terms used a program prepared for road traffic have been
obtained (vertical stress σ in the upper part of the Esplanade and the deflection of the Dk are
Z
the parameters achieved).
The following alternative among the studied ones is selected:
• 30 cm ballast (E = 600 MPa)
• 25 cm of soil treated with cement (E = 4,000 MPa)
• 20 cm of soil stabilized with cement (E = 250 MPa)

This solution has been implemented in a test section with good results. Several years later,
different values were measured and compared with the ones obtained in a traditional section.
The seats of the railroad ties varies between 0,40 and 0,50 mm. The results are in similar orders
of magnitude in both sections. The stiffness increase measured is 17% higher in the case of
stabilized soils. Probably a longer term project will be necessary in order to obtain more and
best results.

International Congress on High-speed Rail: Technologies and Long Term Impacts - Ciudad Real (Spain) - 25th anniversary Madrid-Sevilla corridor 245