The harm of perennial frozen soil to the pipeline exporting the crude oil from Mohe county to Daqing city

XING Yi-Xin，BAO Xin-Hua，YANG Ya-Fei，WANG Peng，XIN Xin

(1.Institute of Environment and Resources in Jilin University，Changchun，130026;2.Institute of 904 Engineering Investigation，Heilongjiang Province，Harbin，150027)

1 General information ofstudying area

1.1 Geography，terrain and landform

The pipeline which starts at the Mohecounty and finishes at Daqing county is 926.83 kilometers in total track length.The terrain is higher in southern and lower in northern.The north is the mountain terrain of Daxing'anling，the central is the hill，the sourth is Songnen plain.The mountain terrain of Daxing'anling is the width of 200～300 kilometers，the height above sea level is 1100～1500 meters.There are many gullis development in the mountain terrain.The majority is the rolling round valley.The quaternary strata develops in the valley，which is primarily the gravel soil，the upper sedimentary organic matter of cohesive soil.It can become the surface vein flow down relative water-resisting layer and underground perched water，forming type valley marshes.The surface lithology is mainly composed of granite，forms a large mountain after denudation.Its two grade of slope is asymmetric，the west side of the mountains is gently sloping to the Mongolian plateau，the east landform step down to the edge of Songnen plain.The stratum along the pipeline is widely distributed，the most development is the department of chola，the cretaceous and the quaternary.

1.2 Climate and hydrological conditions

The climate of this area belongs to continental monsoon climate and changing of four seasons is obviously[1].The obvious climatic characteristics is that winter is cold and dry，summer has high temperature and is rainy，spring and autumn season two climate are changeful.

The pipeline goes through 11 large and mediumsized rivers，whose tributary is dense，widely distribute to the hydrologic network.The pipeline mainly goes through the two drainages of Heilongjiang and Nen river.

1.3 The harm of perennial frozen soil to the pipeline exporting the crude oil

Because of the function，frozen heaving and uneven settlement of foundation，and the cracks in hydraulic facilities，impellers，even causing hydraulic facilities disrepair[2].The typical representative is the following:The landmark is located in the Daqing city of Heilongjiang province zhaoyuan country Maoxing town，transfer station area belongs to the area of sun rises(Fig.1).

Fig.1 The relation between the seasonable frozen soil and the pipeline[3]

Near the point at which a low-lying terrain，physiognomy unit belongs to the low plains，the geological disaster is located in the pipes upper hydraulic facility.Regional annual average temperature 4.2℃，most of the average temperature 18.5℃，extreme minimum temperature 39.2℃，the climate characteristics of the decision on the permafrost is seasonal frozen soil，the frost in 1 to 2 meter，frost heave rate for level 3.Due to function of frozen heaving and uneven settlement of foundation，the hydraulic cracking facilities at the same time，impellers，forming two large cracks，5 cm wide，1.2 meter high respectively，20 cm wide，1.2 meter high.Winter is in the low temperature，soil moisture content is the main disaster inducing factors.Stability is poorer，hydraulic facilities damaged phenomenon has a tendency to gradually expand，will e-ventually cause hydraulic facilities broken.Therefore，we suggest that arranging personnel inspection to check，monitoring of hydraulic facilities damage，when it is necessary to take the corresponding protective measures(Fig.2).

Fig.2 the plane of the disaster caused of frozen soil[3]

Fig.3 Section of the disaster caused of frozen soil[3]

2 Degree of geological disasters in partition

2.1 The high prone areas

The typical area is the amount of wood river-Xiufeng forest farm area.The area is as long as 26.35 kilometers，across the greater Xing'an mountains region Mohe county of Heilongjiang province，the Riverside forest farms，the forest farms of victory and so on，belonging to the jurisdiction of Tahe Qingguan station.Terrain fluctuation，belong to low mountain landscape，height above sea level 254～647 meters or so，the relative height of 30～110 meters.Due to the continental and Marine alternating high and low pressure and monsoon，the climate change is obvious.In general，the long winter is dry and cold;Short，hot and humid summer;The spring wind and little rain;Sharp，cool autumn frost come early.

The area belong to high latitudes in permafrost regions，and its distribution is discontinuous island permafrost，the frozen soil types are mainly less frozen soil，frozen soil and full of frozen soil;Strata are mainly in the quaternary loose debris，the main lithology is peat clay，silty clay and silty sand，sandy clay，gravel，sand，silt mass silty clay and silt，etc;Local bedrock exposed surface is given priority to with sandstone，andesite and granite.The general activity is tectonic，earthquake intensity is for＜Ⅵdegrees.The main human engineering activities are housing，roads，etc.

There are frozen geological disasters of 90，county road waterlogging of 26，Slope waterlogging at 4，Geothermal landslide at 1，in total of 121.The highest disaster risk level is 81，the higher is 29，the middle is 10，the low is 1.At the same time，there is possibility of a collapse of geological disasters.

2.2 The middle prone areas

The typical area is district in southern bank-the forehead wood，the north of the river in Heilongjiang province.

The length is 12 kilometer in this area，in xing-an town of the greater Daxing'anling mountains region of Mohe county in Heilongjiang province，affiliated to the Tahe Ging'guan station.Terrain ups and downs is bigger，belong to low mountain landscape，height above sea level 200～420 meter or so，the relative height of 200 meter.The area belongs to cool continental monsoon climate.As a result of continental and Marine monsoon alternately，microclimate change multiterminal，significant difference was found in the local climate.Along the pipeline on the climatic regionalization belongs to the moderate zone along the river plain.

The area belong to high latitudes in permafrost regions，and its distribution is discontinuous island permafrost，the frozen soil types are mainly of frozen soil，frozen soil less.Strata are mainly in the quaternary loose debris，main lithology is silty clay，silty sand，sandy clay，gravel，sand，silt mass silty clay，silt，etc;Local bedrock exposed surface with sandstone，andesite，sandy mainly andesite and granite.The general tectonic activity，earthquake intensity is for＜ Ⅵdegrees.The main human engineering activities for housing.

There are frozen geological disasters of 15，county road waterlogging of 2，Slope waterlogging at 1，in total of 18.The highest disaster risk level is 7，the higher is 7，the middle is 4.At the same time，there is possibility of a collapse of geological disasters.

2.3 The low prone areas

The typical area is district from the north of Ne'erkeqi town to Laotiejia area in Heilongjiang province.The length is 96.12 kilometer in this area，from Ne'erkeqi town to Big tree town of E'lunchun region of Inner Mongolia province，affiliated to the middle of Jiage'daqi station.The area along the greater hinggan mountains to the terrain，gradually from northwest to southeast low，hilly region，northwest to southeast in hillock fluctuation，between 300～450 m above sea level，which belongs to cool semi-humid continental monsoon climate.

The distributed area is belong to high latitudes in permafrost regions of the island，frozen soil types are mainly less.Strata are mainly in the quaternary loose debris，the main lithology is black silty clay，silty clay，silt mass silty clay，silt，etc.The general tectonic activity is little，earthquake intensity is inⅥ degrees.

Main human engineering activities are for farming，mining earth，roads，etc.There are frozen geological disasters of 6，county road waterlogging of 2，Slope waterlogging at 5，the field waterlogging of 2，in total of 15.The higher is 1，the middle is 1，the lower is 13.

3 Conclusions

The growth of geological disaster is a geological environment change and a result of the combined action of influencing factors，is constantly changing and developing.It is s long-term work that researching and controling the geological disasters.So I suggest that establishing geological disaster prevention and control management system and increasing geological disaster prevention propaganda.

For some geological disaster with important harmful，engineering anagement should be taken.For relatively small size of most geological disasters，should give priority to simple governance and strengthen monitoring;With large scale and great-devastating disasters，if its engineering management cost is higher，and cannot effect a radical cure，we should choose its recommended[4].

In the line from Mohe to Daqing，geological disaster risk control work should be strengthen in the extreme heavy rainfall climate forecast and evaluation of geological disasters[5]，for key sections and geological disasters have the real inspections and do a good job in the flood prevention work of geological disasters，and regularly carry out geological hazard investigation and planning management work，in case of generation rule，the geologic hazard in the bud.

Along pipeline although the earthquake frequency is relatively low，the intensity is weak，overall in the stable region of northeast China.But the effect on pipeline also want to wait until enough attention.

Controlled by the geological environment conditions，in the future a certain period of time，distribution pattern in geological disaster will not happen big changes.Known and potential geological disaster in certain natural conditions have triggered by may.County road waterlogging，frozen heaving and waterlogging slope of the three mined-out area is specifically to prevent.the late secondary geological disaster caused by human engineering activities will be an important work in the need of the prevention and control.

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