Tangshan area occurred mainly in the southern part, namely in Laoting County, the BogezhuangReclamation Area and Luannan County where sand and water were heavily ejected and in thehigh seismic intensity zone near Tangshan City. Typical earthquake damage to road subgradeand pavement with site conditions are summarized in Table 2.II. Types of Earthquake Damage1. Longitudinal cracksLongitudinal cracks on subgrades and pavement were the most common phenomenon ofearthquake damage. The width of the cracks were generally 10-30 cm and the length rangedfrom dozens of meters to over one thousand meters with a depth of 1-2 m (see Photo 1).Longitudinal cracks were usually found on the shoulders of the roads. Severely damagedsections of the Tangshan-Guye, Hugezhuang-Bogezhuang, and Hugezhuang-Laoting highwayshad many longitudinal cracks, which occurred on the shoulders and pavement with a width up to40-50 cm (see Photo 2). Longitudinal cracks were apt to occur at the joints of old and newsubgrades.1 Highway Planning and Design Institute, Ministry of Communications2 Highway Research Institute, Ministry of Communications612. Transverse cracksSevere transverse cracks occurred on the subgrade and pavement near the Daodi Bridge inthe intensity XI zone. They extended the entire width of the embankment and cut off thesubgrade and pavement with a width up to 50-60 cm.3. Settlement of pavementSettlement of the pavement and subgrade occurred on the Hugezhuang-Bogezhuang,Hugezhuang-Laoting and Lengda highways. The subgrade near Laoting on Lengda Highwaysettled 40-60 cm and trees on the roadside tilted inward over a length of 13 km.4. Cracks, settlement and slide of subgrade at bridgeheadDamage to the embankment at the bridgehead was more serious than at ordinary subgradedue to the high fill and the sliding of the riverbank. The subgrade at the bridgehead in theintensity zones VIII and above suffered various degrees of damage, which usually consisted ofthe embankment sliding toward the river and toward the side slopes, settlement, and longitudinaland transverse cracks. Settlement of the embankment at the bridgehead of the Daodi Bridgeamounted to 1.0 m.Damage was most severe on embankments at bridgeheads filled with silty soils. The 5.0 mhigh embankment at the bridgehead of the Huopao Bridge in the intensity VIII zone was filledwith silty soil, and was deformed and slumped after the earthquake settling about 1.0 m. Theembankment at the bridgehead of the Tuozitou Bridge in the intensity XI zone was also filledwith silty soil with a 1:2 side slope which cracked and settled unevenly after the quake. Four tofive cracks occurred at the same section with a crack width of 5-50 cm. The difference inelevation between the two sides of the cracks was 10-30 cm. The length of road damaged was70 m and traffic was suspended.5. The upheaval of the embankment at the bridgeheadPhoto 3 shows the upheaval of pavement on the embankment, which was caused by thethrust of the bridge span at the bridgehead at the Luanhe River BridgeIII. Earthquake Damage to Culverts Passing Beneath RoadsIn the Tangshan area there were a total of 1,852 culverts of various types, mainly of RC boxtype, with a total length of 17,126 m of which 80 of them with a cumulative length of 767.81 msuffered various degrees of damage. According to the severity of damage to the culverts therewere 4 types of damage.(1) Type I: The main damage of this type was the fracture and collapse of the side wall ormiddle pier of the RC culverts resulting in fracture of the top slab of the culvert and fall of thearch, see Photos 4 and 5. Eighteen culverts totaling 195.20 m in length suffered this type ofdamage.62(2) Type II: The main damage of this type was the tilting and cracking of the side wall ormiddle pier, or severe cracks to the top slab of the culvert or to the arch ring. Thirteen culvertstotaling 123.70 m in length suffered this type of damage.(3) Type III: The main damage of this type was the collapse of the flare wing wall at the inletand outlet of the culvert and severe damage to the water flow appurtenances with only slightdamage to the main structure. Thirty-five culverts totaling 320.19 m in length suffered this typeof damage.(4) Type IV: The main damage of this type was slight damage to the flare wing wall.Fourteen culverts totaling 128 m in length suffered from this type of damage.IV. Causes of Earthquake Damage1. Liquefaction of soil foundations and settlement of soft soil foundationsDamage to the subgrade and pavement occurred mainly in the area south of Tangshan withheavy ejection of water and sand in the high intensity zone. The foundation soil here iscomposed of saturated silty fine sand and soft clay. Liquefaction of silty fine sand took placeduring the earthquake with the ejection of water and sand in a large area and side ditches werefilled flush with ejected sand at severely damaged road sections. Samples of ejected sand weretaken from the side ditches of the embankment and sieve analyses were made and gradationcurves from samples of 4 boring holes were obtained as shown in Figures 1 and 2. Liquefactionof sandy soil or settlement of soft soil was the cause of unequal settlement of the subgrade, aswell as for longitudinal and transverse cracks and sliding of the side slopes.2. Effect of sliding of riverbanksSince an embankment is relatively high at the bridgehead and extends into the riverbankforming a high and steep free face it is more apt to slide and settle unequally. Embankments atbridgeheads filled with silty soil with low plasticity suffered the most serious damage among alltypes of subgrade.3. Inadequate compaction of subgrades and poor drainage of side ditchesNo aseismic measures had been taken for subgrades on most roads in the Tangshan andTianjin areas. Some new roads were inadequately compacted. Water accumulated year round inthe side ditches of some sections of road. Some sections of road which were close to the river,channel, pond and soil of the subgrade were saturated and strength and stability were greatlylowered. All these aggravated the degree of damage.