Some civil engineering knowledge points

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1. Before plastering concrete walls or components, they should be cleaned to remove any grease and dirt from the formwork; if necessary, they can be washed with a 10% caustic soda solution to prevent the plaster from peeling off. 2. If the surface of tile or ceramic grout is contaminated, it can be scrubbed with 10% hydrochloric acid, followed by rinsing with clean water. 3. The main reinforcement at the top of concrete piles should extend into the cap, and its anchorage length should not be less than 30 times the diameter of the main reinforcement; for uplift-resistant pile foundations, it should not be less than 40 times the diameter of the main reinforcement. 4. The minimum width of the cap should not be less than 500 mm. The distance from the edge of the cap to the center of the pile should not be less than the diameter or side length of the pile, and the overhang of the edge should not be less than 150 mm. The overhang at the edge of the strip-shaped cap beam should not be less than 75 mm ； The thickness of the slab for strip footings and standalone pile foundations under columns should not be less than 300 mm. The embedment depth of the cap slab should not be less than 600 mm. 5. The diameter of manually dug piles (excluding the retaining walls) must not be less than 0.8 m. When the clear distance between piles is less than 2 times the pile diameter and less than 2.5 m, sequential excavation should be employed. The minimum clear construction distance for sequential pile excavation shall not be less than 4.5 m, and the hole depth should not exceed 40 meters. 6. Yingfeng Lianhu Plaza Hotel (frame-shear wall structure, 18 floors, without piles): The cost for labor-only services is calculated based on the horizontal projected area as follows:
(1) Formwork installation and removal (including nails and wires): 25 yuan/m2
(2) Reinforcement installation and removal (including binding wires): 15 yuan/m2
(3) Concrete pouring (using a pump): 8.5 yuan/m2
(4) Foundation work: excavation of the foundation pit, brick formwork construction, chiseling of pile heads, backfilling, leveling: 5 yuan/m2
(5) Excavation, leveling, and compaction of soil and stone below ground level, as well as general labor: 1.5 yuan/m2
(6) General labor above ground level: 1 yuan/m2
(7) Bricklaying: 8 yuan/m2
(8) Interior decoration (including plastering, tile installation on stairs and elevators in public areas, and floor leveling): 20 yuan/m2
(9) Exterior decoration (labor cost for stone work adjusted according to market prices): 22 yuan/m2
(10) Roof leveling, insulation, and protective layer installation: 0.5 yuan/m2
(11) Lightning protection system, provision of openings for various specialized teams, and costs related to repairing such openings: 2.5 yuan/m2
(12) Temporary facilities, equipment foundations, and safety measures for proper construction: 2 yuan/m2
(13) Cost of welding rods, grinding wheels, saw blades, and small tools: 2 yuan/m2
(14) Management fees: 10 yuan/m2
(15) Planned profit: 10 yuan/m2
Total unit price: 133 yuan/m2 (excluding taxes).
Additionally:
① Labor for manual excavation, including transportation: 10 yuan/m2
② Bricklaying: 9.2 yuan/m2 for 18-inch thick walls, 6.2 yuan/m2 for 12-inch thick walls, 12 yuan/m2 for 24-inch thick walls.
③ Reinforcement installation and removal: 200 yuan per ton.
④ Formwork installation and removal (based on the total area): 8.5 yuan/m2.
⑤ Concrete pouring (using a pump): 12 yuan per cubic meter.
⑥ Interior plastering: 4 yuan/m2.
⑦ Hourly wage for skilled workers: 30 yuan per hour.
7. Self-compacting concrete: Suitable for waterproof concrete applications in underground and underwater environments. When pouring self-compacting concrete for concrete-filled piles, the following points should be considered in terms of materials: (1) An appropriate type of cement should be selected; cement with low hydration heat is preferable. To reduce the alkali content in the concrete, pure clinker cement should not be used, and fly ash cement or pozzolanic cement can be chosen instead. These two types of cement have high shrinkage, so proper curing is necessary; their grade ranges from 425# to 525#, with a usage amount of 320–400 Kg/m3. ⑵Adding appropriate active materials helps improve the self-waterproofing capacity of concrete. Typical active admixtures include zeolite powder and fly ash. The percentage by which they replace cement is generally kept between 15% and 20%, and the amount of sand used should be taken into account. ⑶The ratio of ash to sand should be selected appropriately. The ash-to-sand ratio represents a quality concept for cement mortar; by choosing an appropriate ash-to-sand ratio, it is possible to obtain concrete with high density and good self-waterproofing properties. With a cement content of 320 Kg/m3 and coarse aggregate in the form of pebbles ranging from 5 to 32 mm, a sand ratio of around 0.36 is generally suitable; together with a cement-to-sand ratio of 1:2–2.5, it is possible to produce self-waterproofing concrete with a water resistance grade of at least S8. ⑷The aggregate should not be too large or too small. The silt content in medium-coarse sand should be below 3%; hard gravel with a particle size not exceeding 25 mm and a silt content of less than 1% should be used. ⑸The water-cement ratio should be appropriate. The water-cement ratio has a significant impact on the compressive strength of the mixture, as well as on the concrete’s waterproofing and impermeability properties. For every 0.02 increase in the water-cement ratio, the strength of concrete decreases by 7-8%. The main measure to reduce the water-cement ratio is to use high-efficiency water reducers (such as naphthalene-based high-efficiency water reducers, resin-based high-efficiency water reducers like SM, etc.). With a dosage of 1%, the water reduction rate can reach 15–25%, and the water-cement ratio can be reduced to below 0.3. Principle of self-compacting concrete: The large amount of calcium hydroxide produced during the hydration process of cement does not contribute to the strength of the concrete. The newly added active components react with this calcium hydroxide in a secondary hydration reaction, thereby producing stable calcium silicate hydrate gels with cementing properties, which enhances the strength and density of the concrete. 8. Placement of underwater concrete: ⑴. The mix ratio of underwater concrete shall comply with the following requirements: ① Underwater concrete must have good workability, and its mix ratio shall be determined through testing ； The slump during pumping should be 180–220 ； The cement usage shall be no less than 360 Kg/m3. ②The sand content in underwater concrete should be 40–50%, and medium-coarse sand is preferred ； The coarse particle size should be less than 40 mm; a two-stage grading can be used if conditions permit. ③To improve workability and retard setting, admixtures should be added to underwater concrete, with a sand-to-lime ratio of 1:1.5–1:2.5. The water-cement ratio must not be greater than 0.55. ④When air-entraining agents or air-entraining water reducers are used, the air content in concrete should be maintained at 3–5%; when pre-mixed concrete is used, the retarding time should be around 6–8 hours. ⑵The following rules shall be followed when pouring underwater concrete: ① At the start of concrete pouring, to ensure smooth drainage through the water stopper, the distance from the bottom of the conduit to the bottom of the hole should be 300–500 mm; this distance can be increased appropriately when the pile diameter is less than 600 mm. ②There is sufficient concrete reserve to allow the conduit to be buried more than 0.8m below the concrete surface in one go. ③The burial depth of the conduit should be 2–6 meters; it is strictly prohibited to lift the conduit above the concrete surface. A dedicated person must measure the burial depth of the conduit as well as the height difference between the concrete surfaces inside and outside the conduit, and record this information in the underwater concrete pouring log. ④Underwater concrete must be poured continuously, with the pouring time for each pile determined by the setting time of the initial batch of concrete. All faults that occur during the pouring process must be recorded. ⑤The top of the pile must not be too low as a result of controlling the amount of water used in the final pouring; the height of the excess concrete that needs to be removed must ensure that the exposed concrete at the top of the pile reaches the desired strength level. ⑶. The construction and use of the conduit shall comply with the following requirements: ① The wall thickness of the conduit should not be less than 3 mm, and its diameter should be between 200–250 mm ； The manufacturing deviation of the diameter should not exceed 2 mm. The length of each segment of the conduit is determined according to the process requirements; the length of the base conduit should be no less than 4 m. Flanges or double-threaded square coupling quick connectors are recommended for the joints. ②When lifting the conduit, it must not get caught on the rebar; to this end, protective triangular stiffening plates or conical flange guards can be installed. ③Before use, the conduit should be assembled, pressure-tested, with a water pressure test of 0.6–1 Mpa. ④The stopcock used should have good water-blocking properties to ensure smooth drainage. 9. Technical requirements for the construction of autoclaved lime-sand bricks: (1) Lime-sand bricks must be left to stand for at least 28 days from the date of production before they can be used in masonry work; it is strictly prohibited to use bricks that have just been taken out of the kiln. ⑵When constructing lime-sand brick masonry, the moisture content of the bricks should be between 8–12%; it is strictly prohibited to use dry bricks or bricks with a saturated moisture content. Watering should be done at least 1–2 days in advance; building work should not be carried out immediately after watering, nor should it be done on rainy days. ⑶For gray sand brick masonry, a mixed mortar with a higher ratio of lime paste is advisable; where conditions permit, a specialized mortar with high adhesion should be used. ⑷The daily construction height of gray sand brick masonry should not exceed the height of one scaffold step or 1.5 m. ⑸For the gray sand brick lintels in mixed structures, reinforced concrete lintels should be used. ⑹Gray sand bricks shall not be used in building components that are exposed to temperatures above 200 degrees for extended periods, subject to rapid temperature changes, or affected by acidic media. ⑺Gray sand bricks have good water resistance; their strength does not change significantly in long-term humid environments. However, their resistance to erosion by flowing water is weak, so they cannot be used in areas subject to such erosion, such as at the outlets of downspouts and under faucets. ⑻. Due to the smooth and flat surface of gray sand bricks, when used in high-rise buildings, earthquake-prone areas, or silo-like structures, in addition to appropriate structural measures, it is also necessary to take measures to enhance the adhesion between the bricks and the mortar. ⑼The gray sand brick masonry should have staggered joints vertically and be laid in an overlapping pattern inside and outside. For solid masonry, a stacking pattern of one row straight and one row offset, a diamond pattern, or three rows straight and one row offset is recommended. Brick columns shall not be constructed using the core-wrapping method. ⑽The mortar filling degree of the horizontal joints in gray sand brick masonry must not be less than 80% ； For vertical joints, grout injection or addition of grout should be used; transparent joints, dead joints, and fake joints are not allowed, and it is strictly prohibited to flush the joints with water. ⑾The thickness of the horizontal mortar joints and the width of the vertical mortar joints in brick masonry should be 10 mm, but it should not be less than 8 mm nor more than 12 mm. ⑿The Clear water walls must be re-sealed with mortar; it is advisable to use a 1:1.5 cement mortar prepared with fine sand. ⒀Gray sand bricks should not be mixed with clay bricks or other types of bricks in construction. ⒁. Except for single-story and two-story residential buildings and temporary structures, hollow block masonry should not be used as load-bearing walls. ⒂For the ring beams of high and multi-story buildings constructed with gray sand brick masonry, they should be installed continuously along the exterior walls as well as on the transverse walls at intervals of about 15 meters, extending 1 meter into the remaining longitudinal and transverse walls. A reinforced concrete ring beam should be installed below the top roof slab (at the eaves), and this ring beam should run along both the inner and outer walls; the steel reinforcement should be no less than 4¢10. ⒃At the four corners of the top floor, below the ring beams, appropriate amounts of corner tie rods should be placed in the horizontal mortar joints every three layers of bricks; the length of these tie rods must be at least one bay wide. Reinforcing bars of 2¢6 should be placed in the horizontal mortar joints two bricks below the top surface of the parapet wall ； The four bricks at the top of the wall should be laid using M5 mortar. Within the horizontal mortar joints of the second layer of bricks beneath the first and second floor sills, it is advisable to install a¢4 rebar mesh; the spacing between the vertical rebars in this mesh should not exceed 60 mm, while the spacing between the horizontal rebars should not exceed 250 mm ； Or, 3¢6 rebar can be installed in the grout, extending at least 500 mm on each side of the wall between windows. ⒄At wall corners and where vertical and horizontal walls meet, tie bars should be installed vertically every 500 mm; the number of such bars shall be no less than 1¢6 per 120 mm of wall thickness, with an embedding length of not less than 500 mm on each side, measured from the joint in the wall. ⒅Reinforced concrete lintels are generally used above door and window openings. ⒆To prevent water leakage from the exterior wall due to insufficient filling of the grout, the wall should be plastered on the outside ； All load-bearing exterior walls must be designed to be at least one brick thick (i.e., 240 mm) ； When using a plain water-based exterior wall, overhangs should be installed at the four corners of the roof. ⒇The infill wall should be connected to the reinforced concrete columns or shear walls; at intervals of about 500 mm along the height of the columns or shear walls (in accordance with the modulus of bricks), 2¢6 connection bars should be provided, with these bars extending at least 700 mm into the wall. (21) When the length of the masonry is greater than 6 m or exceeds twice the floor height, it is advisable to consider installing reinforced concrete structural columns in the middle of the wall. These structural columns should be made of C20 concrete, with vertical reinforcement of 4¢12 and stirrups of¢6@200. (22) Plastering should be carried out seven days after the masonry is completed, and only after the quality of the masonry meets the requirements. Before applying the plaster, the surface of the substrate must be prepared first. The substrate should be cleaned thoroughly, and if it is dry, it should be moistened slightly. A layer of adhesive cement mortar with a thickness of 1–2 mm (ratio of cement: fine sand: construction adhesive = 1:1:1) or some other specialized interface agent should be applied as an interface treatment. After that, a leveling layer made of mortar should be applied to prevent cracking and delamination. (23) For the plastering of the exterior walls of high-rise buildings, steel mesh should be installed at the joints where masonry meets beams and columns, as well as around the frames of doors and windows. The width of the steel mesh must be at least 200 mm; after the mesh is securely fixed in place, then plastering can be carried out ； When the height exceeds 30 m and the exterior wall cladding material is heavy, it is advisable to install steel mesh on the entire upper portion of the wall. It is strictly prohibited to directly hang stone veneers on gray sand brick masonry. (24) In the plaster layer at the junctions of interior walls with beams, slabs, and columns, it is advisable to install steel mesh with a width of not less than 200 mm or apply fiber mesh along the length of the joint to prevent cracking. 10. Testing plan for pile reflection wave method: ⑴. Purpose of the test: To assess the structural integrity of the pile. ⑵. Instrumentation: The testing instruments are of the P model produced by the American company PDI. I. Two T-pile integrity testers are available; the testing equipment and on-site connections are shown in Figure 1. ⑶Basic principle: The basic principle of using the pile reflection wave method to assess the structural integrity of piles is as follows: Stress waves are generated by applying excitation signals at the top of the pile. As these stress waves propagate along the pile, they encounter discontinuities such as defects like honeycombing, mud inclusion, fractures, and holes, as well as the bottom surface of the pile, where reflection waves are produced. By analyzing the arrival time, amplitude, and waveform characteristics of these reflection waves, it is possible to determine the integrity of the pile. ⑷. Testing standards: The testing is carried out in accordance with the relevant provisions of the industry standard of the People’s Republic of China, namely the \"Technical Specifications for Testing Building Foundation Piles\" JGJ106—2003. ⑸On-site work: ① Chisel away any loose mortar from the top of the pile, or saw off any damaged parts of the precast pile’s top, so as to expose a fresh, dense concrete surface; ensure that the top of the pile is flat. For cast-in-place piles, create three evenly shaped areas with a diameter of 10 cm at a distance of 10–20 cm from the edge of the pile, in the shape of an isosceles triangle ； ②Remove debris, trash, mud, and standing water from the top of the pile to keep it clean and dry ； ③Before testing, the reinforcement shall not be tied at the pile cap. ⑹Progress schedule and result submission: Under normal circumstances, approximately 100 piles in a city can be tested using the reflection wave method per day. After the on-site inspection is completed, preliminary test results will be provided within two days; once all pile inspections are finished, a formal test report will be issued within seven working days. Hammer striking, pile integrity testing, signal input, parameter setting, data processing, result processing, piles, computer, plotter. Figure 1: Schematic diagram of the on-site connection of instruments and equipment for pile reflection wave method testing. 11. Requirements for quality assurance documents in construction projects: (1) Rebar: For each batch delivered to the site, there must be a factory certificate of conformity (if it is a copy, it should bear the red seal of the manufacturing company); samples must be taken immediately for testing, and the material can only be used after a test report confirming its compliance is obtained – it is not allowed to use it first and then conduct testing. Steel bar testing standards (as shown in the table below): Building material name and specification, Number of samples to be tested, Remarks. Tensile strength; Length: 60 cm, 3 samples. The manufacturer’s name of the steel material must be indicated on the testing form. Original steel material: ≥Ф18, Weight ； Classified by furnace/tank (batch) and diameter; cold bending test: 3 pieces of 40 cm in length, tested in batches; at least 1 sample per 60 tons is required for testing. Tensile strength: 3 pieces of 30 cm in length, tested each time ； For cold-rolled ribbed steel bars delivered in the same batch, those with a diameter ≤Φ16 shall be inspected at least once. Cold bending test: 3 specimens, each 30 cm in length. Tensile strength test: 3 specimens, each 60 cm in length. Except for double-sided welding, single-sided welding, flange welding, and electroslag pressure welding – as well as welds on steel bars with a diameter of ≥Φ18 – all other cases require cold bending tests on 3 specimens per layer; or at least one set per two layers. For sections with seams, there must be at least one set per layer. ≤Φ16 cold bending inspection: 3 pieces, each 30 cm long. Note: ① For imported steel, chemical analysis tests and retest reports are required. ②If the raw material tests or welding tests fail, double the number of samples must be submitted (or sampled) for retesting. ③, Random inspections by quality supervision authorities: One inspection for buildings with a construction area of less than 5,000 m2 ； For foundations and main structures larger than 5,000 m2, sampling inspections are conducted once each. ⑵.Cement: ① Test each batch upon arrival at the site ； Ordinary bagged cement: testing should be conducted at least once for every 100 tons ； At least __ times, 500 tons of bulk cement shall be sent for testing. ② Quantity for inspection: The cement delivered to the site must come with a factory certification (original), and 20 bags shall be sampled on-site immediately, with 0.5 kg taken from each bag. 6 kilograms must be sent for testing; it can only be used after a satisfactory test report is obtained. It is not allowed to use it first and then send it for testing, nor to use it while simultaneously sending it for retesting. ③ Cement that has been in storage for more than three months shall not be used in foundations or the main structure of a building. ④ Random inspections by quality supervision authorities: One inspection for buildings with a construction area of less than 5,000 m2 ； For foundations and main structures larger than 5,000 m2, sampling inspections are conducted once each. ⑶ Gravel and sand: ⑤ Each batch of 400 m3 shall be considered as one inspection unit, with no less than 1 set to be sent for testing ； For unit projects with a value of less than 2 million yuan, there should be no fewer than 2 sets ； For construction projects with a value of over 2 million yuan, there should be no less than 3 sets ； Re-sampling is required when changing the source of sand and gravel. ⑥ Quantity for testing: Sand: 15 kilograms per group. Stone: 10 kg per group for 1–2 cm ； 20 kilograms per group is used naturally. ⑦ Inspection by quality supervision authorities: One sample group is selected for buildings with a construction area of less than 5,000 m2 ； For foundations and main structures larger than 5,000 m2, one sample set is taken for inspection from each. Wall materials: ⑧ Frame structure: At least 1 set per construction project with a cost of less than 2 million yuan ； For construction projects worth over 2 million yuan, there should be no less than 2 sets. ⑨ Brick-concrete structure: no less than three sets per unit project. ⑩ Each batch of wall materials entering the site must be strictly approved by both parties, with the certification document being filed as part of the quality assurance records. ⑪ Number sent for testing: 25 pieces of uniform size and quality per group. ⑫ Inspection by quality supervision authorities: One sample set is taken for each unit project. ⑷. Concrete blocks (age 28 days): ①. At least one set per work shift (for mixing concrete with the same mix ratio) ； ②. For every 50 m3 of concrete prepared (with the same mix ratio), at least one set is required ； ③. For cast-in-place floors (with joints, with each joint considered as a separate unit), there shall be no less than one set per floor ； ④. Each floor of columns (with joints taken as a unit project) shall have no less than two sets ； ⑤For concrete cast-in-place piles with a diameter of less than 600 mm, there must be at least one set every 20 piles ； ⑥For concrete cast-in-place piles with a diameter of 600 mm or more, there must be at least one set per pile. ⑸. Masonry mortar (age of at least 28 days) ； Each floor (for load-bearing walls or partition walls) shall have at least one set, and mortar of different grades shall each have at least one set; for walls with joints, one set per joint. Note: Plastering mortar may be omitted (it is not allowed to use clay-based mixed mortar for plastering). ) ⑹. Waterproof materials: The materials meet the required standards and come with factory certification; for important projects, samples are sent for testing as required by the quality supervision authorities. ⑺Aluminum alloy doors and windows: Testing is required for real estate construction projects and public construction projects (Letter from the Municipal Quality Supervision Station [98‑11]). There are two doors per set, and three windows per set. ① For unit projects with a construction area of 1,000 m2 or less, one sample set each shall be taken for doors and windows ； ② The building area of each unit project ranges from 1,000 m2 to 3,000 m2; for doors and windows, two sets each of different varieties, models, and specifications are sampled for inspection ； ③ The building area of each individual project ranges from 3,000 m2 to 5,000 m2; for doors and windows, four samples each of different types, models, and specifications are taken for inspection ； ④ The building area of each unit project ranges from 5,000 m2 to 10,000 m2; six samples each of different varieties, models, and specifications are taken for inspection for doors and windows ； ⑤ For unit projects with a construction area of over 10,000 m2, eight sets each of different varieties, models, and specifications shall be sampled for doors and windows ； ⑻. Curtain walls: The inspection of building curtain wall projects shall be carried out in accordance with the provisions of Municipal Quality Supervision Letter [98‑12]. ⑼. Pile foundation inspection (Document No. Dongjianzi [1998] 23 issued by the Municipal Construction Commission): ① Small strain measurement: A. For general industrial and civil buildings, the number of piles to be inspected shall be no less than 15% of the total number of piles, and at least 10 piles ； B. For high-rise buildings (buildings with 12 floors or more) as well as important industrial and civil buildings, the number of samples inspected shall be no less than 20% of the total number of piles, and at least 10 piles ； C. The sampling rate for multi-story and high-rise buildings using single-pile or single-column foundations is 100% ； D. If it is confirmed that the construction quality of precast piles is guaranteed, the sampling rate for small strain monitoring can be reduced as appropriate. ② For testing under vertical static load: Precast pipe piles, as well as cast-in-place pile foundations with a diameter of 600 mm or less (including driven, vibrated, drilled cast-in-place piles and other cast-in-place piles), and drilled (percussed) cast-in-place piles with a length greater than 30 m must undergo vertical static load tests to determine their single-pile bearing capacity, in addition to small-strain tests for assessing integrity. The proportion of piles subject to such testing shall not be less than 1% of the total number of piles under the same conditions, and at least 3 piles per construction project must be tested in this manner ； ③ If necessary, large-strain dynamic testing or ultrasonic testing using buried pipes should be carried out; the number of samples taken shall be no less than 5% of the total number of piles, and in any case not less than 5 piles ； ④ Concrete core extraction: For cast-in-place piles other than those covered in item 2 of this pile foundation inspection, in addition to a comprehensive flow property assessment using small-strain testing, core extraction inspections must also be carried out. The number of samples taken for such inspections shall be no less than 5% of the total number of piles, and at least 5 piles in total. ⑤ If non-compliant piles are detected in the pile foundation, additional random inspections shall be conducted. The number of such additional inspections shall be determined through consultation among representatives from the construction (supervision) party, the design party, and the quality supervision party, but it must be no less than twice the number of non-compliant piles. Core sampling of the main structure concrete (Letter from the Municipal Quality Supervision Station [98‑1]). ⑥ Sampling requirements: For each construction unit, one set of columns and one set of slabs shall be sampled. ⑦ Number of samples inspected: three specimens per group. ⑧ Re-inspection: Re-inspection is required for projects where the lowest value of the strength of the sampled core samples is less than 85% of the designed strength grade, and where the average plate thickness is less than 90% of the designed value, or where the lowest value is less than 85% of the designed value. The number of retests is five groups for columns and three groups for plates. The column reinspection areas must include the columns on the first floor and the second floor. ⑽. Certificate of conformity and certification sheet for semi-finished products upon leaving the factory. ⑾Mix proportion: The mix proportion for concrete and masonry mortar is determined once for each design grade, and it must be redetermined when the source of raw materials changes. Concrete pouring work shall not be carried out without a mix design report. 12. Garden knowledge: Though gardens come in many forms, there are nine essential elements: space, light and shadow, separation, accentuation, imagery, color, climate, scent, and fruit offerings. The way of gardening is, in truth, the way of nature. The essence is one: creating a landscape by taking advantage of the existing conditions is like adding the final touch to a painting. Space is something that is everywhere; there are suggestive spaces, such as those behind high walls or in hidden dwellings ； There is a vast expanse of space, like an abyss behind the house. Other elements such as depth, the interplay of high and low levels, and the ability to convey a sense of scale within smaller spaces are all part of the spatial layout. Light and shadow are, in fact, a matter of direction; facing the sun or away from it results in a completely different appearance of the scenery. Like under the light of the sun and moon, where the shadows of flowers shift on the walls; banana trees cast shade by the window, plane trees provide shade across the ground, and locust trees offer shade in the courtyard. It is merely the use of light and shadow that can give rise to endless artistic effects. Creating visual elements is akin to adding the finishing touches to a painting; it involves using ancient vines, old trees, platforms, seats, fences, or walls, as well as pavilions, corridors, galleries, terraces, artificial hills, fish ponds, small bridges, and similar elements in key areas of the garden such as courtyards, patios, plazas, and intersections. These elements help to shape the landscape and provide focal points for viewing.