The Characteristics And The Reclamation Potential Research On Damaged Land In Wenchuan Earthquake

On May12,2008, an8-magnitude earthquake occurred in Wenchuan has posed aserious challenge to sustainable use of land resources in the affected areas. A lot ofarable and construction land were damaged. The deficiency of land resources and thecontradiction between supply and demand are exacerbated. To carry out reclamationof damaged land is a good to effectively restore the amount of arable land, improvethe quality of arable land, and promote the rehabilitation and upgrade of the overallagricultural production capacity.This thesis takes Beichuan Qiang Autonomous County as the study subject toanalyze the characteristics of damaged land from three aspects, the earthquake impact,secondary hazards and post-camp force. The author of this thesis discovered thatearthquake caused arable land cracking, collapsing, upheaval, and infrastructurecollapse, but soil layer had not been damaged much; the landslide objects which weregenerated by secondary hazards made surface folds, upheaval and topsoil whichcaused arable land erosion, but the soil still made up to more than50%, and thecondition was good; debris flow directly covered the arable land, and rainfall madethe surface full of stones with a diameter of about5cm, a few reaching15~20cm.Below the debris flow are the compacted mud and sand which do not have a strongwater permeability and lack organic matters. Dammed lake flooded the arable landand washed away the topsoil that make the arable surface be covered with a lot ofmud. The minimal soil layer is thin and is short of fertility, but the terrain generally isflat. The post-camp force damage on land is mainly in dig pressure and dig loss.Generally it occupies the smaller slope and large area of arable land, and because ofground compaction and hardening, pollution by sewage, some areas lose the arablecapability, but the damage to the soil is not much.By analyzing the soil samples, it discovers that the soil of the study area inbetween the layer of ash and sediment layer has the ability of farming crops. The PHvalue of the damaged land in study area is7to8, which comprises to the standard forthe arable land with the PH value6to8. Through the test, it is found that the effectiveN, P, K and organic matters （mg/kg）in are54.49,22.97,93.97and16.28g/kg respectively in average, of which the effective N reaches the grade Ⅲ standard, theeffective K achieves the gradeⅡsoil standard, and the effective P reaches the grade Isoil standard. The detection about the amount of eight heavy metals in soil, namely,Cu, Pb, Zn, Cr, Ni, Cd, As and Hg, finds that the average amount（mg/kg）is177.37,36.24,500.47,187.28,146.79,11.92,50.25and1.07. Except that the amount of Cd,As and Zn exceeds the standard amount, all the oter meets the standard at grade ⅡorⅢ.This thesis analyzes about the damaged land from the following two aspects, thepossible geological disaster risks and the suitability of reclamation, and it discoversthat the geological structure of the studied area is relatively stable, and it is suitablefor reclamation in terms of economy, natural conditions, basic conditions and socialelements. It determines to take the natural conditions, basic conditions andsocio-economic conditions as the three target layers. By using the evaluation systemto evaluate the potential of reclamation, it gets the conclusion that reclamationpotential value of the study area is3.34, which is higher than the land consolidationand reclamation standard of Sichuan earthquake stricken areas, a value of3.25. All ofthese indicate that the study area has a large reclamation potential. At the same timethe fuzzy comprehensive evaluation method is adopted to take a comprehensiveevaluation on the study area, it tells that the natural condition of the study area valuesat natural0.46to the maximum, and the corresponding rating is excellent. The basicconditions value at0.32to the maximum, and the corresponding rating is good. Thesocio-economic conditions value0.34to the maximum, and the corresponding level isexcellent, which also shows that the potential of reclamation of the study area is great.