| The slope farmland of the whole country has a total area of359million Mu, whichaccounts for1/5of the total farmland. The soil and water loss area of slope farmlandaccount for just6.7%of the total soil and water loss area, but the erosion amountaccounted for28.3%of the country’s total erosion amount. The slope farmland is the mainsource of soil and water loss. Among them, the basic soil characteristics of the rock-soilmountainous region of north China, the rock-soil mountainous region of southwest China,southern red soil region of south China and the qinghai-tibet plateau are with thin soil layer.Because of the thin layer, those slope farmland is not suitable for building a high standardof level terrace, the traditional way to control soil and water loss of thin layer slopefarmland is using farming method, but those methods had some disadvantage such as lowstandard, high casualness and poor effects. A kind of once for all engineering technology isin urgent need to solve the difficult problem which had plagued China’s for a long time.According to the characteristics of development, evolution and harm of slope erosionfrom surface erosion to gully erosion, we came out with the basic technical principle andtechnical ideas to solve soil and water loss of thin slope farmland. Technical principle isbased on the development and evolution law of slope soil erosion from the occurrence ofsplash erosion and surface erosion to gully erosion (gully erosion of the soil erosionamount is2-3times of surface and splash erosion amount, and it account for50-70%of thetotal slope erosion amount) and the basic characteristics of critical slope length, the fieldengineering measures which allow surface erosion and reduce gully erosion were designedto control soil erosion amount at a certain range. Technical ideas:(1) According to idea ofimplementation of "block, filter, drainage " to the project slope runoff train, we designedthe field block and water soil discharge technology for wave-slope soil type and field blockand underground drainage technology for straight slope;(2) On the basis of slope type and combining with the characteristics of slope runoff implementation project of “cutting,permeability(or cutting), drainage”, we put forward the rock wall cutting slope andpermeability of rainfall technology for straight slope type;(3) In order to overcome theinstability and maintenance difficulties of “filter” technology, we proposed the idea of“block, sedimentation, drainage” and put forward the cement laid stone masonry block andsedimentation and underground drainage technology.The experimental runoff plots were set to evaluate the effect of soil and waterconservation, a comprehensive evaluation of all the technologies was made according tothe result of two years’ observation. The main conclusions are as follows:1. As the field block and underground drainage technology for straight slopedesigned, artificial high infiltration (gravel) layer and underground drainage facilities(double-wall corrugated pipe) were set up at critical slope of straight slope field to safelydischarge runoff and ensure the security of the field. In2012, the total runoff was1.296m3,it was1.49times of the conventional tillage annual runoff; Erosion amount was99.02kg,it was1.77times of that in conventional tillage erosion; In2013, the runoff was3.58m3, itwas2.08times of the conventional tillage; Erosion amount is669.93kg, it was1.92timesof conventional tillage. The measures were effective to intercept and discharge runoff andreduce the erosion caused by the runoff at the beginning of the test, however, with thepassage of time, the gravel filter pore was blocked with silt, as results, the infiltration ratewas down and the runoff infiltration reduced sharply. This lead to a bigger erosionintensity caused by runoff. So this measure is not successful and should be redesigned.2. As the rock wall cutting slope and permeability of rainfall technology for straightslope type designed, rock wall was set up at the critical slope of straight slope field and thereverse slope was set up just below the rock wall to shape a capacity to contain runoff. Thiscan effectively reduce the formation of gully erosion and the erosion amount as well.In2012, the annual runoff volume was0.538m3, it was61.69%of the conventional tillage.The erosion amount was99.02kg, it was just6.13%of conventional tillage erosion; In2013, the runoff volume was0.95m3, it was81.89%of conventional tillage, The erosionamount was21.23kg, which is just2.4%of conventional tillage. The technology caneffectively reduce the slope erosion which most of them were caused by super infiltrationrunoff in the north of China, at the same time, in view of the slope erosion caused by filling up runoff in the south of China, we proposed the ditch drainage on the reverse slopeexperiment design to solve the problem of suitability in different place in China.3. The cement laid stone masonry block and sedimentation and underground drainagetechnology for wave slope has a very good effect on water storage and sand block, it is anengineering measure with good prospects. In2012, the total runoff volume was0.01m3,which was just2.73%of the control plot. The erosion amount was0.03kg, which was just7.09%of the control plot; In2013, the total runoff was1.82m3, which was39.52%of thecontrol plot, the erosion amount was126.21kg, which was49.16%of the control plot.This technology can reduce the speed of runoff and the rate of erosion through block ofrunoff. Most of the sand carried by runoff sediment before the cement laid stone masonrywall and water flow was discharged out of field through underground drainage tubes afterfiltered by gravel layer. As a result, the formation of runoff and erosion rate was bothreduced.4. The mortar-laid-stone interception was launched in critical slope length ofWaveform slope mortar-laid-stone works interception slope Precipitation and drainagetechnique, pooling of water to reduced the water flow speed, leaving the sediment carriedby stream to precipitation, and then use the drain which is designed in different height ofinclined upward the supernatant fluid into soil drainage tubes, and the water dischargeslope, the sediment deposition in the cross wall directly. The runoff volume in2013is0.18m3, is2.48%of the control plot, erosion amount is0.89kg, is0.15%of the control plot.The measures can effectively reduce the slope runoff erosion, precipitation and sediment,reduce erosion.5. The cost analysis of mature technology testing scheme was launched. The actualconstruction of cross wall cut slope measures, such as slope grade10°, reverse slope5°,the cost of the measure is￥929per acre, saved78.74%compared to traditional rock ridgeterrace. When actually building waveform-slope slurry masonry precipitation and drainagetechnology, distance calculated at15m, layout overall length of44.4m per acre, theaverage cost is1887yuan per acre, save56.81%compared to traditional rock ridge terrace. |
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