In water conservancy projects, river engineering accounts for a large proportion. Rivers are natural containers and pipelines for water storage and drainage, so the safety of rivers plays a vital role in flood control and flood fighting, and the construction of retaining walls is the most important in river engineering. This paper expounds its construction method. Keywords: earthwork; Foundation; The main working procedures of retaining wall construction in backfilling river engineering are: earthwork, foundation treatment, rubble masonry, backfilling, etc. The key process is rubble masonry. 1 Earthwork of earthwork retaining wall must meet the construction requirements of permanent earthwork, and the compaction of each layer shall not exceed 200mm to ensure sufficient stability and compactness. The engineering quality and artistic modeling should meet the design requirements, and at the same time, the relevant technical regulations and the structural requirements of the original design should be observed in the construction. Land leveling requirements must be set according to the design elevation, and the sedimentation coefficient of earthwork should be considered when determining the stakes, and the elevation error should be controlled within 0.05m 1. 1 earthwork excavation 1. 1 construction preparation before earthwork excavation, the underground and ground obstacles in the construction area should be cleaned and treated. Clean up the operation area, ensure the operation of construction machinery, determine the route, and take measures to reduce the groundwater level. 1. 1.2 The determination of slope depends on the soil condition, and the slope depends on the excavation depth and soil quality, which should be strictly implemented during excavation. If the slope stability cannot be guaranteed due to quicksand and other phenomena, measures such as inserting steel plates or supporting baffles can be taken for protection. 1. 1.3 excavation of foundation pit (groove) will reasonably determine the excavation sequence, route and depth, and carry out earthwork excavation in the riverbed according to the site conditions, and then carry out excavation of retaining wall foundation. Adopt different methods and machinery to shorten the construction period and complete the project with good quality and quantity. 1. 1.4 earthwork excavation shall be carried out by layers and sections from top to bottom, and a certain slope shall be prepared at any time to facilitate drainage. 1. 1.5 spoil is not on the upper side of the excavation scope in principle, otherwise the stability of the excavated slope should be ensured, and spoil should be piled up continuously, and measures should be taken to prevent the accumulated water from collecting on the slope surface and toe. The protective layer of 1. 1.6 is reserved for the easily weathered and disintegrated soil layer of the wall foundation and bank slope. If backfilling cannot be done in time after excavation, 30cm protective layer shall be reserved when excavating the wall foundation. This protective layer should be excavated manually. When cleaning the foundation surface, all thin and soft silt, roots, weeds and rocks should be removed. Deep pits and caves that need to be backfilled should be backfilled and compacted with coarse sand or gravel. 1.2 The filter layer after earthwork backfilling revetment shall be laid together with the backfill soil, and the backfill soil shall be made of cohesionless particles with good water permeability and large internal friction angle as far as possible. Gravels and stones should be properly mixed when using foundation to excavate soil materials; Before filling the soil, make statistics on the original facilities and trees, report to Party A, move or excavate according to Party A's opinions, and clean up the caves on the foundation soil or the roots, garbage and other sundries on the basement surface; Do a good job in soil quality testing. The type and particle size of backfill materials, cleaning and inspection of whether there is any miscellaneous base layer, layered compaction inspection of soil, compaction inspection, trimming and acceptance of layered soil paving materials, and water content of soil materials are controlled within the design range; Fill should be paved in layers: the thickness of each layer of soil should be determined according to the soil quality, compactness requirements and mechanical properties; Filling of filter material transition section: the filling of filter layer should be flush with the filling surface of retaining wall. When the filter layer is connected with the dam shell, it can also be filled in zigzag, but the design thickness of the filter layer must not be encroached. The filling construction parameters of the filter layer shall be determined through tests and implemented after being approved by the supervisor. Compaction of the joint between the filter layer and the dam shell can be carried out by vibrating flat grinding. The running direction of the drum should be parallel to the interface, and the core soil should be prevented from being brought to the filter layer and being polluted. 2 Foundation treatment The foundation of the mortar rubble revetment must be seated on a solid foundation, and the buried depth can be appropriately adjusted according to the soil conditions of the foundation, but it should not be less than1.2m. When the original riverbed is excavated to the design elevation, the flaky with a thickness of not less than 0.5m must be rammed in the soft foundation such as silt, and the foundation should be reinforced with wooden stakes if necessary. 3. After foundation pit excavation and mortar rubble foundation treatment, the size and elevation of the basement should be checked and reported to the supervision engineer for foundation laying after acceptance. The wall is built with 7.5 cement mortar rubble, and the rubble thickness is not less than 15cm. The foundation and abutment are connected by stalagmites to strengthen the combination between foundation and abutment. Settlement joints shall be filled with asphalt mortar. 4. After the foundation is laid, the wall is laid. The wall is made of 7.5 # cement mortar masonry stone, the thickness of flaky is not less than 15cm, and the water surface and top are made of M7.5 mortar masonry. 4. 1 material requirements 4. 1. 1 Stone grade shall meet the requirements of drawings or quality inspection and supervision engineers, and the stone shall be taken from quarries with qualified finished products. Stone should be tough, dense, firm and durable, with appropriate and detailed texture, uniform color and no weathering, peeling, cracks and structural defects. In addition to meeting the above requirements, the thickness of flaky should not be less than 15cm. Not suitable for oval or thin people. 4. 1.2 mortar mortar strength grade should meet the design requirements. Cement, sand and water used in mortar shall comply with the regulations. The sand in mortar should be medium sand or coarse sand, and the maximum particle size of sand should not be greater than 5mm when used for masonry flaky (it should not be greater than 2.5mm when used for masonry block stone and coarse stone). 4.2 Wall Masonry 4.2. 1 The basic requirement is to clean the stones before masonry and keep the cushion clean and moist. The stones should be placed on the freshly mixed mortar and fixed in place. All mortar joints should be filled with mortar. All stones should be laid in layers. When laying in sections, the elevation difference between adjacent sections shall not be greater than1.2m. Expansion joints or settlement joints shall be set between sections, and the horizontal joints of each section shall be consistent. 4.2.2 Laying-out by hanging lines: formwork shall be made according to the design size of retaining wall, and each layer of stone shall be checked by hanging lines, so that the inner and outer lines are straight, the outer line slope is 1: 0.2, the water surface slope is 1: 0.25, and the slope is gradually closed. In the process of construction, it is necessary to regularly correct the wire rod to ensure that the dimensions of each part of the masonry meet the requirements of the drawings. Masonry sequence: first build the corner stone, then build the middle stone, and finally build the belly stone. Corner stones should be made of square stones with neat processing, stable placement and accurate angle, and laid accurately and carefully; Wall rubble should be laid in layers, generally 2 ~ 3 layers form a working layer, and each working layer should be roughly leveled. In general, when building with cement mortar, the width of flat joint and vertical joint is not more than 40mm, and when building with small stone concrete, the width is 30 ~ 70 mm Vertical joints can be filled with stones, and the thickness of stones is not wider than the thickness of joints, and the stones are wrapped with mortar. The masonry of the first flaky should use larger stones, and the largest and flattest side should be closely connected with the foundation, and the stress should be uniform. Small stones shall not be stuffed under the flaky, and the foundation surface shall be cleaned before laying, and mortar shall be combined with water. The settlement joint of the wall is vertically connected with the settlement joint of the foundation and filled with asphalt mortar. The subsection position of each working section should be at the settlement joint, and the horizontal joints of each section should be consistent. The elevation difference of adjacent sections shall not exceed1.2m. After jointing, strengthen health preservation. After its strength reaches 70% of the design strength, the back of the wall can be backfilled, and it is forbidden to make a smooth surface for the slope inside the wall. Every 2.5 m, a drainage hole is staggered up and down, and the drainage hole adopts 90mmUAPVC pipe.

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