Method for compacting expansive soil roadbed

Abstract

The invention discloses a method for compacting an expansive soil roadbed. The method comprises the following steps: preparing test pieces by adopting a wet process, testing the CBR of the test pieces different in water contents one by one, drawing a CBR-water content curve to obtain a curve for showing the change of the CBR of expansive soil along with the change of the water contents omega 1, omega 2, omega 3, omega 4 and omega 5, selecting a point with the CBR value being greater than or equal to 3% in the curve, wherein the water content omega of the expansive soil corresponding to the point is used as a control water content of field compacted soil, and obtaining the soil sample dry density corresponding to omega by performing a compaction test, wherein the soil sample dry density corresponding to omega is used as a roadbed compacting control dry density rho. Through the method, the expansive soil with the relative high natural water content easily achieves the compaction control water content and dry density, so that the purposes of fully, reasonably and directly using expansive soil filler, guaranteeing the construction quality of the expansive soil roadbed and quickly constructing can be achieved. The method is simple, convenient to operate, good in water stability, suitable for compacting soil roadbeds manufactured by poor fine-grained soil such as expansive soil, high liquid limit soil, and red clay, and capable of greatly increasing the utilization rate of the poor soil filler.

Description

technical field [0001] The invention discloses a method for compacting expansive soil roadbeds, in particular to a method for determining the compaction of expansive soil roadbeds with the maximum bearing capacity as the target. The invention belongs to the technical field of highway expansive soil embankment construction methods. Background technique [0002] Expansive soil is a kind of highly plastic clay rich in expansive clay minerals and having obvious water swelling and water shrinkage properties. The expansive soil in the southern region has a high natural moisture content, is difficult to compact and has poor water stability, which is a kind of bad soil quality. [0003] According to the current roadbed design specification in our country, the embankment filler must meet the bearing capacity (CBR) requirements. This technical measure plays a very important role in ensuring the construction quality of expressways. However, there is no clear control standard for expa...

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Problems solved by technology

At the same time, because the maximum dry density obtained by dry compaction test is relatively large (such as Ningming expansive soil dry compacted maximum dry density is 1.82g / cm 3 ), the specification requires that the dry density of the compacted filler should reach more than 93% of the maximum dry density, thus making it more difficult for the expansive soil to meet the compaction requirements

Even if every effort is made to meet the optimum moisture content and compaction standards determined by the dry compaction test, the lower the moisture content of the expansive soil, the greater the dry density and the greater the expansion potential of the soil. The ability to absorb moisture is stronger. Through long-term water vapor migration, the moisture content of the subgrade increases significantly, the dry density decreases significantly, and significant expansion deformation occurs, which greatly reduces the stiffness and bearing capacity of the subgrade (the best moisture content of dry compaction and the bearing ratio CBR measured under the dry density state is less than 3%), causing deformation and damage to the roadbed and pavement

Therefore, the existing roadbed compaction methods have technical problems of poor water stability and low bearing capacity, and, so far, there is no good solution to the compaction of expansive soil roadbeds at home and abroad, and lime improvement or spoil replacement is often used. method, the former is expensive and the construction period is long; the latter causes a large amount of land to be borrowed and spoiled, and the ecological environment is destroyed

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