Research On Properties Of Rammed Earth And Reinforcement Effect Tests Of Earthen Sites

Exposed environment of Northwest China causes basal sapping and corrosion of rammed-earth earthen sites.This kind of deterioration causes cavities on the bottom of earthen sites,and then form stability failures.Reinforcement measures using rammed earth are main methods to improve stability.While there still lacks research on rammed earth materials’ performance evaluation,stability evaluation and tests of reinforcement.Research of this dissertation is divided into three parts: properties of rammed earth,analysis of stability changes of reinforcement and tests for evaluation of reinforcement.Firstly,experiments were conducted for the regulation of properties changes of rammed earth due to the differences of rammed earth densities and curing ages.Relationships between salt and lime content and properties of rammed earth were also investigated.Secondly,two-dimension models of earthen sites with basal corrosion were built on the basis of field surveys on the Great Wall sites of Ming Dynasty in Yulin Shaanxi.Finite element method is used to calculate stability improvement through reinforcement.Quantitative evaluation was conducted to reveal the effect of properties changes,rate of corrosion and rate of reinforcement.Thirdly,possibility and feasibility of in-situ test on surface color and strength of reinforced areas of earthen sites is tested by instrument modification,indoor experiments,field applications and data processing,complementing analysis and evaluation methods towards reinforcement.The results are lists as follows:There exist some regulations of properties changes of rammed earth.On the basis of outcomes of our research,Shrink ability and permeability are basically stable for a 14-day-old rammed earth,and slaking characteristic of rammed earth comes to stable with 60 days curing age.Strength of rammed earth increases sharply on the beginning and come to stable gradually.This provides evidence for evaluation of properties of rammed earth and quality evaluation of reinforcement.Increase of salt content causes improvement of strength and reduction of water stability.Increase of lime content causes significant strength improvement of rammed earth and color changes on the surfaces.Therefore,it is better to lower the lime content,provided that the strength is sufficient.Good improvement of stability is shown by reinforcement towards earthen sites.Stability coefficient comes to stable soon after reinforcement.Under similar circumstances,just simple and low-rate reinforcement has good effect on improving stability.This provides reference to reduce the degree of human intervention during the reinforcement process.Systematic random sampling and statistical analysis fits in-situ surface tests of earthen sites.Surface areas with no holes and cracks and with lower than 3%-4% roughness rate fit for sampling for color test.More than 16 sampling points in an area 30cm*30cm should be tests to improve accuracy.Analysis on normal distribution regulation of data arrays should be conducted to guide scientific color prediction of different surface areas,reinforced ones included.With some certain restriction,penetration test fits for in-situ tests for horizontal compressive strength.Test results are affected by density and moisture content of rammed earth,which is still complicated and vague.In general,In-situ test methods for quantitative analysis of color and qualitative analysis of strength are investigated.Influences of rammed earth properties and reinforcement methods on results of reinforcement were analyzed.Results of this dissertation provide evidences and references for evaluation of reinforcement and properties.Besides,n-situ test methods for quantitative analysis of color and qualitative analysis of strength are also investigated.