Analysis On Influencing Factors Of Real-time Moisture Content Test In The Process Of Intelligent Compaction

High-speed railway is one of the development directions of our country’s"new infrastructure"policy.At present,the intelligent compaction technology（IC）is considered to be an important part of the intelligent construction of high-speed railways in our country,which judges the quality of subgrade compaction based on the measured value of vibration compaction.It has received extensive attention from researchers.However,the technology does not consider the impact of moisture content on the compaction quality of the roadbed,resulting in inaccurate testing and low precision of intelligent compaction technology in practice.Therefore,the introduction of real-time water content test in the intelligent compaction process is of great value to improve the test accuracy and ensure the quality of subgrade compaction.Resistivity method is considered to be a possible way to test soil moisture content in real time.This paper takes the water content test of the intelligent compaction process of the high-speed railway foundation as the research object,designs the compaction test and explores the relationship between apparent resistivity,compaction index,and water content in combination with the field test,fits the relationship,and builds some test models.The main innovations achievements are as follows:（1）The hypothesis based on considering the seepage characteristics of the soil and ignoring the cementation of the three-phase material is studied through the finite element method.When the compaction load of the roadbed gradually increases,the relationship between the apparent resistivity and the porosity is consistent with the classical model of the resistivity method.There is a significant negative correlation between apparent resistivity and compaction.（2）The compaction characteristics of soil are closely related to the moisture content.When the soil moisture content is the optimal moisture content,the average soil density,the conventional compaction test index foundation coefficient,and the secondary deformation modulus are the largest;and the soil moisture content can be larger,the index that characterizes the degree of compaction may be less,When the soil moisture content less than the optimal moisture content,the compaction index changes relatively little.（3）According to the apparent resistivity of soil samples with different moisture content under compaction load and the conventional compaction detection index,a numerical relationship model is established.,The relationship between apparent resistivity and water content is fitted with based on a power function relationship model the experimental data.Similarly,there is a linear relationship model between apparent resistivity andK_{3 0}、E_v2 is selected.By simply combining the relational expressions,the moisture content test model is obtained considering the change of compaction characteristics.（4）The determination coefficient of the correlation test is greater than 0.7,between the in site vibration compaction measurement value VCV and the conventional compaction detection index.And it meets the compaction standard indicating that the VCV value can be used as the basis for the evaluation of compaction quality in most areas.According to the calibration test carried out in site about the moisture content test,the optimal compaction process combination is confirmed as static pressure+weak vibration+static pressure+strong vibration+static pressure+weak vibration+static pressure.The measured value of apparent resistivity is chose when the static pressure stage is loading.It has been verified that the water content test model has good applicability in site.In addition,although the VCV value of some measuring points meets the standard,the conventional compaction detection test is unqualified.The reason for the under pressure is that the moisture content is too large.These wet compaction areas should be remarkable that the moisture content test is larger than optimum moisture.（5）For large continuous areas,the continuous water content test model is established based on the VCV test data and the apparent resistivity,water content at the measuring point.After comparison with the measured value of the drying method,it is clear that the established relationship model has a positive effect.The wet compaction areas must be effectively monitored where the VCV value meets the standard,but the conventional compaction detection index could not meet.These examined wet compaction areas have improved the level of intelligent and refined construction.