Case Application at Tianjin Port

Technology of marine environment information support and service for ports and shipping at Tianjin Port

Field observation and investigation at sea

Considering marine environment support required by Chinese offshore ports and marine oil and gas exploitation, the project sets the establishment of the monitoring and forecast system of sediment transport and deposition, coast and beach stabilization and sudden deposition brought about by storm as one of its main focuses. In order to achieve such a purpose, field survey is conducted for sediment transport at Tianjin Port during spring-neap tides on the basis of the stereo-monitoring system of the offshore marine dynamic environment in Bohai Gulf, so as to gain a comprehensive understanding of the sediment concentration and distribution in entrance and export at Tianjin Port, grasp basic marine current knowledge by survey and provide data foundation for numerical modelling. The implementing institution of the project conducted field surveys for marine current and suspended sediment concentration of the given station in August and November 2010, respectively. Relevant computation and analysis are conducted according to the measurement results after the survey [130, 131].

Execution specification and standardization

The Specification for Offshore Observation (GB149114-2006-T);

The Specification for Oceanographic Survey-General Rules (GB-12763.1- 2007);

The Specification for Oceanographic Survey-Marine Hydrographic Observations (GB-12763.2-2007);

The Specification for Oceanographic Survey-Exchange of Oceanographic Survey Data (GB012763.7-2007);

Code of Hydrology for Sea Harbour (JTJ213-98);

The Specification for Marine Monitoring (GB17378-2007);

Sea Water Quality Standard (GB3097-1997).

Survey of meteorology and hydrology

Meteorological conditions

1) Temperature

Temperature at Tianjin Port is shown in Table 7.1.

2) Precipitation

Precipitation at Tianjin Port is shown in Table 7.2.

TABLE 7.1: Temperature at Tianjin Port

Annual mean temperature

12.3°C

Annual maximum temperature

16.2°C

Annual minimum temperature

9.1°C

Extreme maximum temperature

39.9°C (July 24, 1955)

Extreme minimum temperature

— 18.3°C (January 17, 1953)

TABLE 7.2: Precipitation at Tianjin Port

Annual mean precipitation

586.0 mm

Annual maximum precipitation

1083.5 nrnr (1964)

Annual minimum precipitation

278.4 nrnr (1968)

Maximum daily precipitation

191.5 nrnr (July 30, 1975)

3) Wind

The prevailing wind in this region is E-direction wind, with an occurrence frequency of 11.71%, followed by S-direction wind, with a frequency of 10.34%; the frequency of E-direction wind above grade 6 (inclusive) is 1.96%; the frequency of wind above grade 6 (inclusive) in all directions is 3.65%.

4) Thunderstorm

Number of average annual thunderstorm days is 27.5, thunderstorm weather most frequently occurs in June and .July.

5) Fog

Number of average annual days of heavy fog with a visibility of shorter than 1 km is 16.5; fog whether most frequently occurs in autumn and winter and dissipates quickly after sunrise.

According to statistics, actual number of days of heavy fog with a visibility of shorter than 1 km is 5.0.

6) Relative humidity

Average relative humidity at Tianjin Port is 65%; maximum relative humidity is 100%; minimum relative humidity is 3%.

Hydrologic conditions

1) Tide

Tide observed in this region is irregular semi-diurnal tide, whose (Hoi +

Hki)/HM2 = 0.53.

a) Location relation among various datum planes

The relation of local theoretical lowest tide level with datum level of Dagu and local mean sea level is shown in Figure 7.1.

b) Tide-level characteristic value

Annual highest high-tide level: 5.81 nr (September 1, 1992)

Annual lowest low-tide level: —1.03 nr (November 10, 1968)

Note: The lowest low-tide level: —1.08 nr occurs in December 18, 1957 Annual mean high-tide level: 3.74 m

Tide-level relation

FIGURE 7.1: Tide-level relation

Annual mean low-tide level: 1.34 m Annual mean sea level: 2.56 m

Annual maximum tidal range: 4.37 m (October 1980)

Annual mean tidal range: 2.40 m

  • c) Designed water level Designed high water level: 4.30 nr Designed low water level: 0.50 m Extreme high water level: 5.88 m Extreme low water level: —1.29 m
  • 2) Marine current

Tidal current in the port region is reversing current. Marine current of the port is almost parallel to the waterway axis; current velocity of flood tide is greater than that of the ebb tide.

3) Sea ice

Sea ice of different thicknesses is observed on waters of the port region; the icing period, which lasts for around 60 days, starts from late December and ends in late February. According to statistics over the past years, average days of severe ice period stands only at 10. In normal years, sea ice exerts almost no impact on port operation and ship navigation.

Survey of sediment scouring and sedimentation

As the biggest comprehensive port in north China, Tianjin Port covers a land area of 53 km2 and has a waterway depth of 19.5m, total water and land area of 200 km2 and various berths of over 140. In 2005, it had a cargohandling capacity of 240,000,000 tons and a container-handling capability of

  • 4,800,000 tons standard boxes, which ranks 6th among the global ports and 16th among the container ports in the world respectively [132].
  • 1) Geological conditions

Survey suggests a law in the soil-layer distribution at Tianjin Port: the soil can be divided into three layers from top to bottom: dredger fill formed by artificial hydraulic reclamation; sludge and mud clay formed by marine sediment and shell-mixed cohesive soil; silt and silty-fine sand, silt and silty clay, silt and silty-fine sand formed by estuarine delta facies sediment [133].

2) Sediment scouring

Tianjin Port is located in the silt coast of Bohai Gulf. Under the wind and tide effects, a large volume of silt sediment deposits in the port and waterway. Back silting of sediment of the port has been a common concern of the world ever since its construction.

Before the construction of gate in the estuary of Haihe River, a main source of the sediment of the port is silt discharged downward from the estuary of Haihe River in flood season. The port transports 8,000,000 tons of silt every year. As the port is close to the estuary, the phenomenon of silt discharged downward entering the port by taking one tide is observed, which has a remarkable influence on the sedimentation at the port. After the completion of the gate in the estuary, the Haihe River was transformed into a waterway-based reservoir. Most of the water and silt are stored in the waterway, with only a small amount of them being discharged downward. In recent years, almost no silt is discharged. With the disappearance the primary silt source, wave-raised sediment and tidal current-transported sediment brought into the port by the rising wave. As the sea area has a weak tidal dynamic, suspended sediment transportation will not occur under the effect of a single tide in small- or no-wave weather. Hence, a huge wave is the main dynamic factor for the formation of suspended sediment on the beach. Under the effect of huge waves, sediment is evenly distributed in the water and is deposited slowly, and the impact will last for a longer period. A moveable float sludge layer forming on the bottom exerts an enormous influence on the waterway depth and water quality in the surrounding sea area. So far as deposit inten- sit.y is concerned, annual sediment volume in the port reaches about 6,100,000 m3, with 3,300,000 m3 in the port basin and another 2,800,000 m3 in the waterway. The port basin has greater deposit intensity than the waterway. The thickness of bottom floating sludge layer of North Port Basin of Dongtu Dyke in 1993 to 1994 alone reached 1.2 m.

Under the efforts launched since the end of 20th century in the improvement of waterway ability at Tianjin Port to 150,000 tons, the port has become one of the largest artificial deep-water ports in the world. Enormous dredging and maintenance efforts are required by Tianjin Port, in order to ensure smooth navigation in the waterway. Actual measurement suggests that a volume of 400 million m3 of sludge had been dredged at Tianjin Port from 1952 to 2002.

Through efforts made in the research and project implementation over the past several decades, the sludge has been reduced significantly. The ratio (m3/t (handling capability)) between sludge dredging volume and annual handling capability at Tianjin Port saw a decline to 0.08-0.09 in 1990s, lower than that of the Port of Rotterdam in Netherlands in 1980s of 0.115 (Table 7.3).

TABLE 7.3: Measured stations and measurement elements

Station

Latitude

Longitude

Measurement element

01

38°57.059'A'

117° 53.889' E

Marine current, sediment content

02

38°57.380'A'

117° 52.148' E

Marine current, sediment content

03

&38°58.071'A'

117°47.651'E

Marine current, sediment content

04

38°58.385'A'

117° 46.225'A

Marine current, sediment content

According to latest research. Tianjin Port has become a light back-silting port. Back silting of sediment is no longer a constraint for the development of the port. Instead, millions of cubic meters of back silt produced each year has become a crucial resource for reclaiming land in the port. It is expected that with the further improvement of sediment environment of the port and the implementation of effective treatment measures, silt sediment in the port will be further reduced.

Despite the alleviation of sediment intensity under huge dredging and sludge-reducing efforts, Tianjin Port displays the characteristic of two sediment peaks in a year, which occurs in the flood season and wind season, in which periods of floating sludge is commonly seen in the anchorage of the waterway. Hence, it is not easy to guarantee the water depth required by navigation, as sludge is continuously produced despite the routine dredging work. Therefore, establishing the forecast model and high-precision forecast system for sediment transport and shore stability of the port is of great importance to waterway rectification, silt sediment distribution adjustment and port safety support.

Implementation of marine survey

Ocean University of China, the implementing institution of the project, has conducted a survey on marine current and sediment in the periods from August 10 to 20, 2010, and November 20 to 30, 2010, respectively.

1) Monitoring station

In order to learn the basic characteristics of sediment content and movement in Tianjin Port, four survey stations are set up as shown in Figure 7.2.

2) Investigation periods

Survey and observation during the entire cycle of the continuous spring and neap tides selected in wet season were conducted in August 2010;

Observation during spring tide was conducted from August 11 to 12;

Observation during neap tide was conducted from August 17 to 18;

Survey and observation during the entire cycle of the continuous spring and neap tides selected in the dry season were conducted in November 2010;

Observation during spring tide was conducted from November 21 to 22;

Observation during neap tide was conducted from November 28 to 29;

  • 3) Observation layers
  • 6-point (namely surface layer, layers at water depths of 0.2H, 0.4H, 0.6H, 0.8H, respectively, and bottom layer) method is adopted.
Distribution of monitoring stations

FIGURE 7.2: Distribution of monitoring stations

  • 4) Key technical indicators of the survey equipment
  • a) Marine current investigation

SCL-9 direct-reading current meter: measurement range of current velocity: 0.03-3.5m/s. mean measurement error ±2%; measurement range of current direction: 0° to 360°. mean measurement error ±10°;

b) Sediment investigation;

Pressure-type water sampler. Water samples of various layers will be taken with the pressure-type water sampler at the site, for indoor analysis and weighing. Water sample of sediment will be taken with a pressure-type water sampler for six layers. After the water sample is taken, the sample bottle will be washed three times before holding the sample and being sealed and recorded. The volume of water sample taken is 1000 ml to 2000 ml. The water samples taken will be transported to the laboratory for filtering and analysis on the same day when the sampling is conducted. The filtered water volume, calibrated diaphragm setting and other technical issues of each station are determined by filtering tests in accordance with relevant national specifications such as Specification for Oceanographic Survey—Marine Geology and Geophysics Survey (GB/T 13909-92). Imported filter membrane with a bore diameter of 0.45 and vacuum filter are adopted; the container is washed with deionized water after seawater filtering is finished; salt-leaching is conducted with the filter membrane three times, with 50 ml distilled water consumed each time. Scale used for weighing in the laboratory has a precision of 0.1 mg/1. The analysis is conducted according to relevant specification. The blank filter membrane and suspensoid are weighed several times; weighing error between two successive measurements shall be within 1 mg/1 (i.e., 0.1 mg/1 order of magnitude). A double-layer calibrated diaphragm is set for 54 water samples in the water sample filtering, which is in line with the requirement of 20% in the specification governing suspensoid survey.

5) Investigation method

The survey is conducted according to Specification for Oceanographic Survey (GB/T 12763.2-2007) and Specification for Marine Monitoring (GB/T 17378.4-2007).

 
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