Analysis of Difficulties in Mountainous Building Construction

Analysis of Difficulties in Mountainous Building Construction

Due to the particularity of the terrain of the mountain building project, the construction organization of the whole project is different from the general flat project. So, what are the difficulties in mountain building construction?

The main features of the orogenic project are large topographic relief, many platform elevations and large drop. The construction difficulties of mountain construction projects are mainly reflected in construction organization, construction road traffic organization, material transportation organization and temporary drainage.

Keywords: mountainous area; Difficulties in construction; Support; drainage

1 Characteristics and Construction Difficulties of Mountainous Building Engineering

The main characteristics of mountain construction projects are large slope and large drop. Therefore, different from ordinary projects, the construction difficulties are mainly manifested in six aspects: slope retaining wall support, earthwork, various foundation forms with complex geological conditions, material transportation organization, road traffic organization and temporary drainage. (1) The project is located on the steep slope of the valley. In order to form a building platform and ensure the safety of the slope, a large number of slope supporting projects are designed, which have various forms and are difficult to construct. The main forms are anchor and shotcrete support, stone retaining wall, gabion retaining wall and natural greening slope; (2) The original landform of the project site is a steep valley, and the original planning and design consider the situation according to the mountain. The positive and negative zero elevation of each building is different. The villa occupies a small area, the platform working face is fragmented, and there are a large number of high slopes and high retaining walls. The excavation slope control and slope flatness control of natural greening slope and shotcrete slope require high requirements, and the platform earthwork construction is extremely difficult and has a long period.

(3) The characteristics of mountain engineering are complex and diverse geological conditions, and different foundation forms need to be selected according to different geological conditions. Moreover, the geological exploration report can not fully and accurately reflect the detailed and true geological conditions of the site, and there are many geological faults, which often lead to great differences in the geological conditions of the same building. In the field construction, contact the design unit in time to deal with the drawing changes when problems are found; (4) Due to the great change of site height difference, it is difficult to transport materials horizontally and vertically under the condition that mechanical construction can't cover them and construction roads can't reach them. Especially in outdoor engineering and retaining wall engineering, the problem of material transportation is particularly prominent because there is no tower crane to cooperate with the construction, so it is necessary to build temporary access roads and use forklifts and excavators to cooperate with multiple transshipment;

(5) The mountainous engineering site fluctuates greatly, and the road layout in planning and design is restricted by many factors. There is only one road in the two rows of buildings, and they are all broken roads, which cannot form circular traffic. Therefore, the site construction is greatly influenced by the site and traffic. Construction access roads need to be adjusted many times in different construction periods. For example, in earthwork construction, the construction access road needs to be constantly adjusted according to the on-site construction sequence, and because the temporary access road has a large slope, construction vehicles will not be able to pass in rainy days, which will affect the earthwork construction period; (6) Because the site is located in the valley area, the surface water flow in rainy season is more urgent and faster than that in general leveling works. When the rainstorm comes, the mountain torrents collected in each valley have large flow, great impact and destructive power, which has great influence on construction and serious consequences.

2 mountain construction project experience summary

Through the engineering practice of this project, the following experiences are summarized.

2. 1 Overall construction sequence

Due to our previous lack of construction experience in mountain construction projects, we failed to predict the difficulty of this project, and failed to do a good job in the overall construction organization of mountain construction projects, especially failed to comprehensively consider the construction sequence of the main building structure, retaining wall structure and surrounding outdoor pipelines. This brings the following problems: (1) In order to grab the first batch of pre-sale nodes, the main project is constructed first, and then the high retaining wall is constructed, which greatly increases the construction difficulty. During the construction of high retaining wall, the top line of the excavated slope is very close to the main structure, and no slope support is formed, which almost endangers the safety of the main building under construction, and the construction is extremely passive.

At the same time, the construction of retaining wall directly leads to the excavation and occupation of the first group of construction access roads, which leads to the inability to transport materials, the stagnation of the main structure construction and the delay of the total construction period; (2) The height difference between the high platform and the low platform is 6 ~ 1 1 m, and the width of the two platforms is very narrow, so it is extremely difficult to advance and retreat mechanically and transport materials during the construction of the high retaining wall, and it is impossible to synchronize multi-point construction for the sake of early construction, which leads to a long construction period and great hidden dangers in slope safety and cross construction during the construction of the retaining wall; (3) Although the intersection with pipeline construction was considered in the construction of retaining wall, some pipelines were constructed synchronously, and sleeves passing through the retaining wall were reserved, but some pipelines were not arranged for construction first, which led to the need to dismantle some retaining walls in the later pipeline construction, resulting in losses.

Therefore, for mountain construction projects, we must first clarify the relationship between slope support construction and building main body construction. The construction sequence of each project should be determined, and the design drawings such as general layout, outdoor pipe network, slope retaining wall structure and outdoor landscape should be familiar with in advance. During the construction of high retaining wall, the back of the retaining wall and the outdoor pipeline passing through the retaining wall should be completed together to avoid the damage to the retaining wall structure caused by trench excavation in the later period, and some platform machinery can't reach it, so manual pipeline excavation and material handling can only be adopted.

2.2 Earthwork Construction and Earthwork Balance

The topography of this project is steep and the geological conditions are complex. According to the slope drawings, there are many green slopes and shotcrete-anchor supporting slopes, so it is necessary to accurately control the slope ratio, top line and toe line. There are hundreds of platform elevations on the site, and some stones need blasting construction. Earthwork construction runs through the whole construction process. In order to ensure the smooth progress of earthwork construction, a detailed earthwork construction plan must be made before the construction, and a detailed platform elevation construction drawing should be compiled in combination with the villa civil foundation construction drawings, and technical disclosure should be made on excavation sequence, transportation road organization, earthwork balance inside and outside the site, platform boundary elevation, slope ratio and other contents. In order to avoid overbreak of platform and slope during construction, the excavation of platform landmarks must be strictly controlled.

2.3 Horizontal and vertical transportation of materials

Because the terrain of the project is particularly complex, the buildings are scattered, and there are many platforms with different elevations, the workload of horizontal and vertical transportation of materials is much greater than that of ordinary plane projects, and the problems of horizontal and vertical transportation of materials are very prominent. Therefore, we should fully realize this point in the general layout stage of construction, and a sufficient number of tower cranes must be arranged in the parts where the terrain height difference changes greatly and the outdoor engineering is complicated. In order to ensure sufficient mechanical transportation capacity during construction, the tower crane should cover all parts of the whole site as much as possible. It is best to install the tower crane before the construction of the main foundation of the building, and then dismantle it after the outdoor garden construction is basically completed. In the general layout stage of construction, attention should also be paid to the location and positioning of tower crane equipment, which should not only facilitate the traffic organization of on-site construction, but also make the tower crane foundation not interfere with the future outdoor structure and pipeline construction as much as possible, so as to create conditions for future interspersed construction in advance.

2.4 Site layout and traffic organization

Special attention should be paid to the construction site layout and road traffic organization in mountain construction projects. Due to the great relief of the terrain and the great change of the site height difference, there is only one passage around the building, and there are a large number of multi-buildings, multi-parts and multi-processes in different construction stages, and the construction road will inevitably be partially blocked or interrupted, resulting in the impassability of construction vehicles. Therefore, the project site layout, road traffic and construction organization must be grasped as a whole.

2.5 Temporary drainage and formal drainage organization

During construction in rainy season, the earthwork on site is often washed away by heavy rain, which causes the following problems: (1) The preliminary consideration of temporary drainage is not careful, and the image of civilized construction in rainy season is extremely poor, which has a considerable relationship with the imperfection of temporary drainage facilities;

(2) Temporary drainage without grit chamber is directly discharged into the municipal drainage system, resulting in a large area blockage of the municipal drainage pipe network. The amount of rainstorm and its influence on the construction area of mountain construction projects are not predicted enough, and the water flow is faster, and the influence is far greater than that of ordinary flat construction projects; (3) During the construction, the main body crosses the outdoor retaining wall, and the temporary drainage is seriously damaged. Therefore, the temporary drainage system did not play a role in the later period, which led to serious water accumulation in many low-lying areas, indicating that we lacked experience in setting up temporary drainage in mountain construction projects;

(4) Some parts of the regular drainage system are not well considered, and the drainage effect is not ideal. For example, the water flow in the valley of the original design is underestimated, the capacity of the ditch at the foot of the slope is insufficient, and the daily cleaning is not timely. During the rainstorm, the sudden increase of water flow leads to untimely drainage, and the phenomenon of earth scouring after overflow is serious. To sum up the above problems, temporary drainage and formal drainage of mountain buildings should be done in the following aspects: (1) Due to the particularity of mountain projects, temporary drainage measures of the projects must be combined with formal drainage, and some formal drainage projects need to be constructed in advance.

The permanent flood drainage system should be constructed before the earthwork excavation of the slope. A flood retaining ditch is set at the top of the high slope outside the red line of the project, a rapids trough is set in the valley, an energy dissipation basin and a grit chamber are set at the bottom of the rapids trough, and a drainage ditch is set at the foot of the slope to introduce mountain torrents into the river to prevent them from rushing into the site and affecting the construction. The primary grit chamber should be added regularly to clean the drainage system. (2) For sections with steep terrain, intercepting ditches with sufficient width are set at intervals on the temporary roads, and the intercepting ditches are connected with the temporary drainage system;

(3) Before rain, protective measures must be taken, such as putting plastic sheets around the materials and the entrances and exits of the basement, building water barriers, etc., to avoid serious consequences such as site pollution, material loss, basement soaking and drainage pipe blockage caused by rain; (4) For low-lying areas and basements that cannot rely on natural drainage, automatic start-stop pumps should be set to pump water, and generators should be configured to avoid soaking.

3 abstract

To sum up, it can be seen that the construction organization of the whole mountain building project is different from the general flat land project because of the particularity of the terrain, which greatly subverts our traditional experience and inertia thinking formed in the general flat land project construction. For mountain construction projects, if these factors can not be solved predictably in the early stage of the project, then the influence of these factors on the whole project will be very fatal during the construction process.

refer to

Lin Yongsheng. On the Development, Construction and Design Method of Mountain Villa [J]. Guangdong Science and Technology, 2012,23 (16):115.

[2] Jiang Jun. Discussion on several common problems in mountain building construction [J]. China Science and Technology, 20 1 1(4):262-263.

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